GPS-Derived Orthometric Heights - PowerPoint by pengtt

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									       GPS-Derived Heights
             Part 1

Development and Description of NGS
            Guidelines



                     NOAA, NOS, NGS
   To understand how to achieve GPS-derived
orthometric heights at centimeter-level accuracy,
       three questions must be answered:

1) What types of heights are involved?
    • Orthometric heights
    • Ellipsoid heights
    • Geoid heights

2) How are these heights defined and related?

3) How accurately can these heights be determined?


                               NOAA, NOS, NGS
    Leveled Height Differences




               B                     Topography


A
                                 C




                        NOAA, NOS, NGS
            Level Surfaces and Orthometric Heights

                                                                          WP
           Level Surfaces                                  P

                                                                      Plumb
                                                                      Line

Mean
Sea                                                                   “Geoid”
Level                                                                   WO
                                                                 PO



   Ocean             Level Surface = Equipotential Surface (W)
                 Geopotential Number (CP) = WP -WO
           H (Orthometric Height) = Distance along plumb line (PO to P)



                                                  NOAA, NOS, NGS
   Heights Based on Geopotential Number (C)

• Normal Height (NGVD 29)                              H* = C / 
       = Average normal gravity along plumb line
                                               dyn
• Dynamic Height (IGLD 55, 85) H                     = C / 45
      45 = Normal gravity at 45° latitude

• Orthometric Height                                   H=C/g
      g = Average gravity along the plumb line

• Helmert Height (NAVD 88)                    H = C / (g + 0.0424 H0)
      g = Surface gravity measurement (mgals)




                                                NOAA, NOS, NGS
   Leveled Height vs. Orthometric Height
                                        h = local leveled differences
                                       H = relative orthometric heights




                      B                                   Topography

                  hAB =  hBC
      A
                                       C

     HA                                HC
             HAC  hAB + hBC




Observed difference in orthometric height,
H, depends on the leveling route.

                                  NOAA, NOS, NGS
       Global Positioning
            System
       27 Satellites
       6 Planes, 55° Rotation
       4/5 Satellites /Plane
       20,183 km Orbit
       1 Revolution /12 Hrs




NOAA, NOS, NGS
                Z
 Zero
Meridian
                     -X
       -Y




                           Y
            X

                               Mean
                           Equatorial Plane

                -Z
                      NOAA, NOS, NGS
    Earth-Centered-Earth-Fixed Coordinates
                            Conventional
               Z Axis        Terrestrial
                                Pole
                                               P   (X,Y,Z)


                                                   Earth’s
                                                   Surface

 Zero
Meridian
                                               Z

                Origin
                (0,0,0)                                            Y Axis
           Center of Mass


                                                     X
                                 Y



X Axis                                     Mean Equatorial Plane



                                           NOAA, NOS, NGS
The Ellipsoid
                      a = Semi major axis
N
                      b = Semi minor axis
                      f = a-b = Flattening
b                           a

     a



               Geodetic Reference System 1980
S         a = 6,378,137.000 meters (semi-major axis)
          b = 6,356,752.3141403 m (semi-minor axis)
         1/f = 298.25722210088 (flattening)


                    NOAA, NOS, NGS
           GPS - Derived Ellipsoid Heights
               Z Axis
                                         P    (X,Y,Z) = P (,,h)
                                   h
                                             Earth’s
                                             Surface

 Zero
Meridian

                                                          Reference Ellipsoid


                                                        Y Axis
                            

                        




X Axis                          Mean Equatorial Plane



                                         NOAA, NOS, NGS
             Ellipsoid, Geoid, and Orthometric Heights
                                   “h = H + N”
                                                                 P
        Ellipsoid                                                         Plumb Line
                                                                h

                                                                Q

Mean                                                                 N
Sea                                                                         “Geoid”
Level
                                                                     PO




   Ocean            h (Ellipsoid Height) = Distance along ellipsoid normal (Q to P)
                    N (Geoid Height) = Distance along ellipsoid normal (Q to PO)
                    H (Orthometric Height) = Distance along plumb line (PO to P)



                                                       NOAA, NOS, NGS
       Ellipsoid Heights (NAD 83 vs. ITRF 97)
• NAD 83:       Origin and ellipsoid (GRS-80)
      a = 6,378,137.000 meters (semi-major axis)
      1/f = 298.25722210088 (flattening)

• ITRF 97: Origin (best estimate of earth’s C.O.M.)
• NAD 83 is non-geocentric relative to ITRF97 origin by
  1 - 2 meters
• ITRF 97 ellipsoid heights: Use a NAD 83 shaped ellipsoid
  centered at the ITRF97 origin
• Ellipsoid height differences between NAD 83 and ITRF97
  reflect the non-geocentricity of NAD 83



                                            NOAA, NOS, NGS
Simplified Concept of ITRF 97 vs. NAD 83


                                            h83
                                                   h97         Earth’s
                                                               Surface




            ITRF 97
            Origin



   NAD 83             Identically shaped ellipsoids (GRS-80)
   Origin
                      a = 6,378,137.000 meters (semi-major axis)
                      1/f = 298.25722210088 (flattening)


                                         NOAA, NOS, NGS
NAD83(86) to ITRF97(97) Ellipsoid Heights (meters)




                              NOAA, NOS, NGS
              High Resolution Geoid Models
• G96SSS
     1.8 million gravity measurements (marine, land, altimetry)
     30 second DTED updated with Canadian Rockies data

     Earth Gravity Model of 1996 (EGM96)

     2 min x 2 min spacing

     International Terrestrial Reference Frame ITRF94 (1996.0)


   GEOID96
     Begin with G96SSS model
     2951 GPS/Level Bench Marks (NAD83/NAVD88)

     Converts NAD83 (86) into NAVD 88

     Relative to non-geocentric GRS-80 ellipsoid



                                       NOAA, NOS, NGS
           High Resolution Geoid Models
            G99SSS (Scientific Model)
• 2.6 million terrestrial, ship, and altimetric
  gravity measurements

• 30 arc second Digital Elevation Data

• 3 arc second DEM for the Northwest USA
      Decimated from 1 arc second NGSDEM99

• Earth Gravity Model of 1996 (EGM96)

• Computed on 1 x 1 arc minute grid spacing

• GRS-80 ellipsoid centered at ITRF97 origin

                                  NOAA, NOS, NGS
NGSDEM99 is a 1 x 1 arc-second Digital Elevation Model (DEM) of the Northwest
United States, covering the region 39 - 49N latitude, and 234 - 265E longitude.



                                                   NOAA, NOS, NGS
             High Resolution Geoid Models
                      GEOID99
   Begin with G99SSS model
       6169 NAD83 GPS heights on NAVD88 leveled benchmarks
       Determine national bias and trend relative to GPS/BMs
       Create grid to model local (state-wide) remaining differences
       ITRF97/NAD83 transformation
       Compute and remove conversion surface from G99SSS

   Relative to non-geocentric GRS-80 ellipsoid

   4.6 cm RMS nationally when compared to BM data

   RMS 16% improvement over GEOID96

                                          NOAA, NOS, NGS
NOAA, NOS, NGS
                                 GEOID99




For the conterminous United States (CONUS), GEOID99 heights range from a low of -50.97 meters
(magenta) in the Atlantic Ocean to a high of 3.23 meters (red) in the Labrador Strait.


                                                         NOAA, NOS, NGS
                     Tidal Datums
• Heights Measured Above Local Mean Sea Level

• National Tidal Datum epoch; 19 year series

• Encompasses all significant tidal periods including 18.6 year
  period for regression of Moon’s nodes

• Averages out nearly all meteorological, hydrological, and
  oceanographic variability

• Leveling is used to determine relationship between bench
  marks and tidal gauges




                                      NOAA, NOS, NGS
NOAA, NOS, NGS
                        Importance of Shoreline
     AL, AK, CA, CT, FL, GA, LA, MD,
     MS, NJ, NY, NC, OR, RI, SC, WA                Territorial Seas

Privately Owned       State Owned                      Contiguous Zone
   Uplands             Tidelands

                                                             Exclusive Economic Zone
                          State Submerged Lands
                                                             Federal Submerged Lands
                                        3 n. mi.                                High Seas
                                                      12 n. mi.
          MHHW                                                    200 n. mi.
                    MHW

                                       MLLW                       Chart Datum



Privately State
Owned Owned                  Privately State
                             Owned Owned
        TX
                           DE, MA, ME, NH, PA, VA                 NOAA, NOS, NGS
 NAVD 88 minus
LMSL (1960-1978)
   (units = cm)




 NOAA, NOS, NGS
         National Geodetic Vertical Datum 1929
                      (NGVD 29)
• Defined by heights of 26 tidal stations in U.S. and Canada

• Tide gages were connected to the network by leveling from
  tide gage staffs to bench marks

• Water-level transfers used to connect leveling across Great
  Lakes

• Normal Orthometric Heights:
      H* = C / 
      C = model (“normal”) geopotential number
       = from normal gravity formula

• H* = 0 level is NOT a level surface


                                          NOAA, NOS, NGS
First-Order Leveling Network NGVD 29




                      NOAA, NOS, NGS
          North American Vertical Datum 1988
                     (NAVD 88)
• Defined by one height (Father Point/Rimouski)
• Water-level transfers connect leveling across Great Lakes
• Adjustment performed in Geopotential Numbers
• Helmert Orthometric Heights:
      H = C / (g + 0.0424 H0)
      C = geopotential number
      g = surface gravity measurement (mgals)
      H0 = approximate orthometric height (km)
• H = 0 level is nearly a level surface
• H = 0 level is biased relative to global mean sea level



                                            NOAA, NOS, NGS
Vertical Control Network NAVD 88




                       NOAA, NOS, NGS
            NGVD 29 Versus NAVD 88
Datum Considerations:         NGVD 29            NAVD 88
• Defining Height(s)         26 Local MSL        1 Local MSL

•   Tidal Epoch                 Various           1960-78
                                                (18.6 years)

Treatment of Leveling Data:
• Gravity Correction        Ortho Correction   Geopotential Nos.
                            (normal gravity)   (observed gravity)

•   Other Corrections      Level, Rod, Temp.   Level, Rod, Astro,
                                               Temp, Magnetic,
                                               and Refraction




                                          NOAA, NOS, NGS
      NGVD 29 Versus NAVD 88 (continued)

Adjustments Considerations: NGVD 29            NAVD 88
•   Method              Least-squares          Least-squares

•   Technique           Condition Eq.         Observation Eq.

•   Units of Measure       Meters            Geopotential Units

•   Observation Type    Links Between         Height Differences
                        Junction Points      Between Adjacent BMs




                                          NOAA, NOS, NGS
    NGVD 29 Versus NAVD 88 (continued)

Adjustments Statistics :     NGVD 29                NAVD 88
•   No. of Bench Marks       100,000 (est)        450,000 (US only)
•   Km of Leveling Data       75,159 (US)            1,001,500
                              31,565 (Canada)


Published Information:
• Orthometric Height Type        Normal             Helmert
• Orthometric Height Units       Meters             Meters
• Gravity Value                  Normal             “Actual”




                                             NOAA, NOS, NGS
Height Differences Between NAVD 88 and NGVD 29




                             NOAA, NOS, NGS
NOAA, NOS, NGS
                Expected Accuracies

• GPS-Derived Ellipsoid Heights
     2 centimeters

• Geoid Heights (GEOID99)
   2.5 cm correlated error (randomizing at 40 km)
   Relative differences typically less than 1 cm in 10 km

   4.6 cm RMS about the mean


• Leveling-Derived Heights
     Less than 1 cm in 10 km for third-order leveling




                                     NOAA, NOS, NGS
       GPS-Derived Ellipsoid Height
               Guidelines

• GPS related error sources

• Pilot projects were used to develop guidelines

• NOAA Technical Memorandum NOS NGS-58




                               NOAA, NOS, NGS
                    Execution of Surveys;
                      Sources of Error

• Errors may be characterized as random, systematic, or
  blunders

      Random error represents the effect of unpredictable variations in the
       instruments, the environment, and the observing procedures employed

      Systematic error represents the effect of consistent inaccuracies in the
       instruments or in the observing procedures

      Blunders or mistakes are typically caused by carelessness and are
       detected by systematic checking of all work through observational
       procedures and methodology designed to allow their detection and
       elimination



                                                 NOAA, NOS, NGS
                           GPS Error Sources
• Precise or broadcast orbit error              • Multipath
       Satellite relationship center-of-mass         Antenna phase center variation
        to L1 antenna phase center
                                                      Circular polarization
• Satellite clock error (nominal)                     L1-L2 phase center offset
       SA dither (minimized)                         Receiver clock offset
       Satellite inter-channel bias                  Receiver inter-channel bias
       L1-L2 antenna phase center offset
       Transmission multipath                  • Height of phase center above mark
                                                      Marker stability
• Ionospheric effects
                                                      Earth tides - direct effect
• Tropospheric effects                                Ocean tide loading
       Dry (hydrostatic) troposphere delay           Atmospheric loading
       Wet troposphere delay                         Crustal motion




                                                       NOAA, NOS, NGS
NOAA, NOS, NGS
The images compare the accuracy of GPS with and without selective availability (SA). Each plot shows the positional
scatter of 24 hours of data (0000 to 2359 UTC) taken at one of the Continuously Operating Reference Stations (CORS)
operated by the NCAD Corp. at Erlanger, Kentucky. On May 2, 2000, SA was set to zero. The plots show that SA
causes 95% of the points to fall within a radius of 45.0 meters. Without SA, 95% of the points fall within a radius of
6.3 meters.
As illustration, consider a football stadium. With SA activated, you really only know if you are on the field or in the
                                                                           NOAA, NOS, NGS
stands at that football stadium; with SA switched off, you know which yard marker you are standing on.
NOAA, NOS, NGS
                 Atmospheric Error Sources

• Ionosphere                            • Hydrostatic (“Dry”)
      Greatest at 1400 (local time)      Troposphere
      Typical 5 to 15 m at zenith            90% of total effect
      Extreme 0.15 to 50 m at zenith         Model accuracy only 2 to 5%
      Higher frequencies have less           Need surface atmospheric pressure
       effect                                  and temperatures
      Error correction by dual               Accurate pressure is critical
       frequency                              About 2.2 m at zenith

• “Wet” Troposphere
      10% of total effect
      Model accuracy only 10 to 50%
      Need humidity along path
      About 20 cm at zenith



                                                  NOAA, NOS, NGS
                  Signal Multipath
• Satellite signal arriving at receiver via multiple
  paths due to reflection (Leick 1995)

• Quasi-periodic signal; 5 to 50 minutes

• Maximum multipath is a fraction of wavelength
      (L1 = 19 cm; L2 = 24 cm) typically 2 cm to 5 cm

• Geometric relationship between satellite, antenna,
  and surroundings

• Same pattern in same satellite geometry on
  consecutive days produces similar results; similar
  effects
                                     NOAA, NOS, NGS
Multipath Delay :                    T = 2hSinø
(meters)                                    c




                                  d(T )ƒ~ hCosø
Multipath Freq. :
                                    dt     3
(Cycles/hr)




                                        h                                            d ø ~ 2 rad.
                                                                                     dt 12 hr.
                                                          ø             ø


                                                           Figure 1
                                                     Multipath Description

                    August 1987 -Ionospheric refraction and Multipath Effects in GPS Carrier Phase Observations
                                  Yola Georgiadou and Alfred Kleusberg
                                  IUGG XIX General Assembly Meeting, Vancouver, Canada
                                                                                NOAA, NOS, NGS
            Equipment Requirements
• Dual-frequency, full-wavelength GPS receivers
   Required for all observations greater than 10 km
   Preferred type for ALL observations regardless of length


• Geodetic quality antennas with ground planes
   Choke ring antennas; highly recommended
   Successfully modeled L1/L2 offsets and phase patterns

   Use identical antenna types if possible

   Corrections must be utilized by processing software when
    mixing antenna types




                                    NOAA, NOS, NGS
            Different
          Phase Patterns



                               Note that SV elevation and
                               varying phase patterns affect
                               signal interpretation differently
Antenna           Antenna
Type A            Type B




                            NOAA, NOS, NGS
          Analyses of Data from Pilot Projects


• Northridge Earthquake Project 1994
   GPS on leveling-derived bench marks
   Two 3-hour sessions

    » On different days

    » Different times of day

   Provided   2 cm results for short lines, i.e. 5 to 10 km




                                    NOAA, NOS, NGS
       Northridge Earthquake Project

                                                   Pearblossom
                        Castaic
Santa Paula




                                      Los Angles



                                               Norwalk




                Palos Verdes      Tidal B


                                  NOAA, NOS, NGS
        Analyses of Data from Pilot Projects

• Harris-Galveston Coastal Subsidence District’s
  CORS and PAMs
     7 stations in a 25 km radius collecting data 24 hours
      a day for 2+ years
     Various length baselines
     24, 6, 3, 2 and 1 hour solutions
     20 minute to epoch-by-epoch solutions
     Real-life influences due to multipath, atmosphere,
      and satellite geometry



                                         NOAA, NOS, NGS
Harris-Galveston Coastal Subsidence District
                               Riverside




                               P2
                                       LAKE HOUSTON
                                                                    CORS
                          P1


        LaGrange                                                P   PAM
                      P3         NORTHEAST
                                                                    GPS Site
                   ADDICKS




                     P4




 Edna




                                                      NOAA, NOS, NGS
Port-a-Measure PAM




   NOAA, NOS, NGS
                                                                     LAKE HOUSTON to NORTHEAST (23 km)
                                                                       ("Hands-Off" Automatic Processing)

                    3




                    2
Up Component (cm)




                    1
                                           Std. Dev. (0.91 cm)


                    0
                         300

                               301

                                     302

                                             303

                                                   304

                                                         305

                                                               306

                                                                     307

                                                                           308

                                                                                 309

                                                                                       310

                                                                                             311

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                                                                                                         313

                                                                                                               314

                                                                                                                     315

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                                                                                                                                                                                       326

                                                                                                                                                                                             327

                                                                                                                                                                                                   328

                                                                                                                                                                                                         329

                                                                                                                                                                                                               330
                    -1




                    -2




                    -3

                                             Day of Year ( 24 hour solutions using 15 degree elevation cut-off value)



                                                                                                                                        NOAA, NOS, NGS
                                                                                                                                          24 - Hour Solutions
                                                          LAKE HOUSTON to NORTHEAST- (23 km)                                                Day 300   -5.15
                                                                                                                                            Day 301   -5.95
                                                    Days 300 - 304; 6 Hour Solutions - With Tropo Modeling                                  Day 302   -5.70
                                                                                                                                            Day 303   -5.97
                                                                                                                                            Day 304   -5.80
                                    0
                                         0


                                             1


                                                   2


                                                           3


                                                                4


                                                                         5


                                                                               6


                                                                                   7


                                                                                         8


                                                                                              9


                                                                                                   10


                                                                                                         11


                                                                                                                 12


                                                                                                                      13


                                                                                                                           14


                                                                                                                                   15


                                                                                                                                             16


                                                                                                                                                      17


                                                                                                                                                                18
                                    -1


                                    -2
                                                                                                   Mean = -3.1
Ellipsoid Height Correction (cm)




                                                                                                                                Day 302
                                                                                                    = 0.5
                                    -3
                                                                         Day 300

                                    -4


                                    -5


                                    -6


                                    -7
                                                                                    Mean = -7.5
                                                                                    = 0.3                                              Day 304
                                    -8
                                                               Day 301
                                                 Day 303
                                    -9


                                   -10

                                                                 Time (0 = 0 to 6 hr, 1 = 1 to 7 hr,....., 18 = 18 to 24 hr)



                                                                                                        NOAA, NOS, NGS
                                                   ADDICKS to PAM 3 (4.2 km)
                                          Days 130 and 131 (3 hour solutions - w/o Sat 15)

                    3.5

                                                                                          Day 130
                                                                             Mean (1.33 cm) / Std. Dev. (0.83 cm)
                    3.0



                    2.5
Up Component (cm)




                                                                              Day 131
                    2.0                                          Mean (1.01 cm) / Std. Dev. (0.47 cm)

                                                1.3
                    1.5


                                                                                                   0.8                   0.9
                    1.0



                    0.5

                                                           0.6
                    0.0
                          3   4   5   6     7    8     9    10   11     12     13     14      15        16   17     18   19    20   21

                                           Time (3 = 3 to 6 hr, 4 = 4 to 7 hr, ...., 21 = 21 to 24 hr)



                                                                                      NOAA, NOS, NGS
                                                     ADDICKS to PAM 3 (4.2 km)
                                           Days 130 and 131 ( 2 hour solutions - w/o Sat 15)

                    4.5
                                                                                           Day 130
                                                                              Mean (1.33 cm) / Std. Dev. (1.15 cm)
                    4.0


                    3.5


                    3.0
                                                                          Day 131
Up Component (cm)




                                                             Mean (1.03 cm) / Std. Dev. (0.58 cm)
                    2.5

                                                 2.0
                    2.0
                                                                                                                          1.2
                    1.5


                                                           0.5                                     0.7
                    1.0


                    0.5


                    0.0
                           3   4   5   6    7    8     9    10    11     12      13     14    15         16   17     18    19   20   21   22

                    -0.5

                                            Time (3 = 3 to 5 hr, 4 = 4 to 6 hr, ...., 22 = 22 to 24 hr)




                                                                                             NOAA, NOS, NGS
                               Day 130
                  Mean (1.02 cm) / Std. Dev. (1.54 cm)




                         Day 131
            Mean (1.05 cm) / Std. Dev. (0.96 cm)

2.0
                                                         1.6




                                             0.2

      0.3




                                   NOAA, NOS, NGS
             Results from Pilot Project
• 24 hour solutions of data taken during “bad” atmospheric
  conditions may not always provide 2 cm results

• 1, 2, 3, and 6 hour solutions will repeat very well from day
  to day when observations are collected at about the same
  time on different days, but may produce significantly
  different results using data collected during different times
  of the days, i.e. having significantly different satellite
  geometry

• Increasing the elevation cut-off angle will decrease the
  effects due to multipath, but it will also decrease the number
  of available satellites which may significantly decrease
  accuracy of short observing sessions

                                       NOAA, NOS, NGS
        Analyses of Data from Pilot Projects

• FGCS 48 Hour Pseudo-Kinematic Network,
 Gaithersburg, MD (June 13 - 15, 1995)
  12 stations occupied in network

     Two TCORS and one rover
     10 minute observing sessions at each site continuously
      over 48 hour time span
     10 different occupations at each site
     Baselines ranged from 100 meters to 26.1 km




                                      NOAA, NOS, NGS
      FGCS 48 Hour Pseudo-Kinematic
                Network        RAPID




                                                          STATIC




                                                      KINEMATIC
                       HOLDAHL




          DICKERSON                                   SURVEY
          (TCORS)



                                                   TS19977
WINGATE
          STRANGE
                                                 NBS 5 (TCORS)
                    REMONDI                     NBS 102
                              LOVE
                                     ANDERSON




                                                NOAA, NOS, NGS
                            Distances to Stations from TCORS
                                                                                                                                RAPID
                                                            RAPID
                                                                                                                                26.1 km
                                                            25.0 km

                                              STATIC
                                                                                                                           STATIC
                                              19.9 km
                                                                                                                           21.5 km

                                         KINEMATIC
                                                                                                                         KINEMATIC
                                          15.0 km
                                                                                                                           17.8 km
                                                                                         HOLDAHL
                          HOLDAHL       SURVEY                                           8.3 km
                                                                                                                      SURVEY
                          16.1 km       10.1 km
          DICKERSON                                                                                                   15.2 km
                                                                            DICKERSON
          (TCORS)
                                                                            (TCORS)
                                        TS19977
                                                                                                                      TS19977
                                        5.1 km
                                                                                                                      15.9 km
WINGATE                                                               WINGATE
25.1 km                                                               9.3 km
          STRANGE                                                            STRANGE                                    NBS 5 (TCORS)
                                                    NBS 5 (TCORS)
           19.9 km                                                            6.9 km
                     REMONDI                                                           REMONDI
                      14.9 km   LOVE              NBS 102                               9.2 km   LOVE                 NBS 102
                                9.9 km ANDERSON   0.1 km                                         12.2 km              19.4 km
                                                                                                           ANDERSON
                                        4.5 km                                                              16.8 km




                                                                                 NOAA, NOS, NGS
NGS 48 Hour Test of GPS Vertical Guidelines (June 13 thru 15, 1995)

Differences of session ellipsoid Heights from mean value; Units = cm
Northern Line from NBS 5                                                               Western Line from NBS 5

  NBS 5        NBS 102    TS19977      SURVEY KINEMATIC        STATIC      RAPID       WINGATE      STRANGE      REMONDI     LOVE       ANDERSON HOLDAHL
   Base        (0.1 km)   (5.1 km)     (10.1 km)   (15.0 km)   (19.9 km)   (25.0 km)    (25.1 km)    (19.9 km)   (14.9 km)   (9.9 km)    (4.9 km)   (16.1 km)
Session 1        0.2         3.8          1.2        2.9          2.8         4.0         -3.0         -1.9        4.2         0.8        -2.8
Session 2        -0.7        3.0          0.9        0.3          2.3         1.6         -0.2          0.3        -1.4       -0.7        -0.3
Session 3        -0.8       -1.2         -0.6        0.2         -1.3        -2.5         17.1 F        5.0 *      1.6         0.5        -1.5
Session 4        -0.4        2.2         -0.3        -1.0        -0.1         0.0         3.6          -0.2        1.9         0.8         4.0         0.0
Session 5        -0.2       -1.7         -1.4        0.6          1.8        -1.0         4.1           1.8        2.0         2.6         0.2        -0.3
Session 6        0.1        -2.4          0.4        1.2         -1.2        -1.2         0.7          10.4 F      -1.0        0.2         0.8
Session 7        0.5         6.6 * H      0.4        -1.4        -2.9        -0.4        -36.6 F       -3.2        -3.8       -0.6         0.0
Session 8        0.1        -2.7         -0.4        -0.7        -0.9         0.1         -5.1 *       -3.1        -1.9        0.0        -1.7
Session 9        0.8        -0.7         -0.2        -0.8        -1.9        -1.1         0.2           0.9        -1.9       -1.3        -1.4        -1.0
Session 10       0.0        -7.3 * H      0.2        -1.1         1.3         0.8         57.0 F        0.2        0.3        -1.8         3.0         1.3

 Average         0.0        0.0          0.0         0.0         0.0         0.0          0.0          0.0         0.0         0.1         0.0        0.0
 Std. Dev.       0.5        3.8          0.7         1.3         1.8         1.7          3.1          2.4         2.3         1.2         2.0        0.8


             F - Could not fix integers - (FLOAT solution) - Not included in statistics
             H - RMS value greater than 1.5                                 Summary:
             * - Difference greater than 5 cm                                 FLOAT Solutions - Large Residuals
                                                                              High RMS Values - Large Residuals




                                                                                                    NOAA, NOS, NGS
         Analyses of Data from Pilot Projects

• FGCS 24 Hour Pseudo-Kinematic Network,
 Gaithersburg, MD (November 28 - 29, 1995)
  12 stations occupied in network

     Two TCORS and two rovers
     Simultaneous 10 minute observing sessions between
      rovers continuously over 24 hour time span
     8 different occupations each site
     Baselines ranged from 100 meters to 26.1 km




                                      NOAA, NOS, NGS
     FGCS 24 Hour Pseudo-Kinematic
               Network         RAPID




                                                 STATIC



                                             KINEMATIC


          DICKERSON
          (TCORS)                           SURVEY




                                          TS19977

WINGATE
                                         NBS 5 (TCORS)
      STRANGE
                                          NBS 102
             REMONDI
                       LOVE              KIN C
                              ANDERSON



                                    NOAA, NOS, NGS
NGS 24 Hour Test of GPS Vertical Guidelines (November 28 thru 29, 1995)

Differences of session ellipsoid Heights from mean value; Units = cm

Northern Line from NBS 5                                                                Western Line from NBS 5

  NBS 5        KIN C      TS19977     SURVEY      KINEMATIC     STATIC      RAPID       WINGATE      STRANGE      REMONDI      LOVE           ANDERSON     NBS 102
    Base       (0.1 km)   (5.1 km)    (10.1 km)    (15.0 km)    (19.9 km)   (25.0 km)    (25.1 km)    (19.9 km)   (14.9 km)    (9.9 km)        (4.9 km)    (0.1 km)
 Session 1      1.9         1.0   H     -0.2         2.0           1.5         3.0         -3.3         -0.7        -0.1         2.1   H        1.3          -1.4 H
 Session 2      0.6         4.0   H     13.1 H       -1.3   H     -0.2        23.4 F       -0.1 H                   -2.9   H    -1.1   H        -2.3   H
 Session 3      -0.8       -4.7   H     -3.1 H       3.5    H     -2.1        -4.1          1.5         0.1 H        5.4   H    -0.7   H        1.9    H
 Session 4      0.5        -5.8   H     -7.0         -4.9   H      2.5 H      -5.0 F                                -1.2        -2.2            -2.0   H
 Session 5      3.1 H      -2.4         2.0          1.0           2.1         0.8         -1.6         -2.7         0.3        -1.8            1.5    H     1.4
 Session 6      -1.5        8.3   H     1.1 H        -0.3          1.6                                  -0.3 H      -1.4         3.2            -0.5   H
 Session 7      -3.5       -0.5   H     1.4 H        -1.4         -5.9 H      0.3           6.9         3.8 H       -4.2   F    -1.4      H     0.4
 Session 8      -0.6       33.3   H     -7.0 H       1.4    H      0.7 H                   -3.6 H                   29.7   F     2.0      H     -0.6   H

 Average         0.0        0.0         0.0          0.0          0.0         0.0          0.0          0.0         0.0          0.0             0.0         0.0
 Std. Dev.       1.9        4.6         6.0          2.4          2.6         2.6          3.6          2.1         2.6          1.9             1.5         1.4

  48 Hour
                            3.8         0.7          1.3          1.8         1.7          3.1          2.4         2.3          1.2             2.0         0.5
  Results
 Difference
                            0.8         5.3          1.1          0.8         0.9          0.5          -0.3        0.3          0.7            -0.5         0.9
24 - 48 Hour




      F - Could not fix integers - (FLOAT solution) - Not included in statistics
       H - RMS value greater than 1.5
                                                                                                     “Bad” Weather
                                                                                                     High RMS Values

                                                                                                     NOAA, NOS, NGS
               Results from Pilot Project
• Base lines with high RMS produced outliers

• Base lines where integers could not be fixed produced outliers

• Standard deviation of a single 10 minute occupation during
  “good” atmospheric conditions was 2.1 cm

• Standard deviation of the mean of two 10 minute occupations
  during “good” atmospheric conditions was 1.4 cm

• Standard deviation of a single 10 minute occupation during
  “bad” atmospheric conditions was larger than a single 10
  minute occupation obtained during “good” atmospheric
  conditions, i.e. 3.0 cm versus 2.1 cm


                                        NOAA, NOS, NGS
        Analyses of Data from Pilot Projects

• San Francisco Bay Demonstration Project
     Test of guidelines and modifications based on results

     Phase I: Static survey test for 2 cm accuracy
       » Mixture of base line lengths; 2 to 50 km
       » Long observing sessions; minimum of 3 hours

     Phase II: Kinematic survey test for 5 cm accuracy
       » Short base line lengths; less than 5 km
       » Short observing sessions; 15 minutes

     “Real-world” conditions, i.e., traffic, trees, buildings


                                       NOAA, NOS, NGS
San Francisco Bay Demonstration Project
                                              R 1393




    941 4873 TIDAL 17         MOLATE

                                    941 4863 TIDAL 5      BRIONE
               RV 223
                                                                             CORS
                              PT. BLUNT
    941 4819 TIDAL 32                      YACHT                             GPS Site

                 941 4290 N             941 4779 ASFB                    0    5     10
                                                PORT 1
                           S 1320                                            KM
                                                 941 4750 TIDAL 7

                                                M 554           CHABOT
                        U 1320
                                                        M 148
                         L 1241                                 N 1197

                                                           WINTON




                                                          NOAA, NOS, NGS
NOAA, NOS, NGS
NOAA, NOS, NGS
Comparison of 30 Minute Solutions - Precise Orbit; Hopfield (0); IONOFREE
(30 Minute solutions computed on the hour and the half hour)                                      Two Days/Same Time
                                                                                                   -10.254 > -10.253
MOLA to RV22 10.8 Km
                                                                                                   -10.251
                                                          Day 264 *               Mean dh *        Difference = 0.3 cm
                 dh      Hours                    dh       minus diff   Mean dh    minus diff
 Day 264                          Day 265
                (m)       Diff.                  (m)      Day 265 >2      (m)      "Truth" >2      “Truth” = -10.276
                                                           (cm)   cm                (cm)   cm
                                                                                                   Difference = 2.3 cm
 14:00-14:30   -10.281   27hrs    17:00-17:30   -10.279    -0.2         -10.280     -0.5
 14:30-15:00   -10.278   27hrs    17:30-18:00   -10.270    -0.8         -10.274      0.2
 15:00-15:30   -10.281   27hrs    18:00-18:30   -10.278    -0.3         -10.280     -0.4
 15:30-16:00   -10.291   27hrs    18:30-19:00   -10.274    -1.7         -10.283     -0.7        Two Days/Different Times
 16:00-16:30   -10.274   27hrs    19:00-19:30   -10.274     0.0         -10.274      0.2
 16:30-17:00   -10.287   27hrs    19:30-20:00   -10.276    -1.1         -10.282     -0.6            -10.254 > -10.275
 17:00-17:30   -10.279   27hrs    20:00-20:30   -10.261    -1.8         -10.270      0.6             -10.295
 17:30-18:00   -10.270   27hrs    20:30-21:00   -10.251    -1.9         -10.261      1.5
 18:00-18:30   -10.277   21hrs    15:00-15:30   -10.270    -0.7         -10.274      0.2            Difference = 4.1 cm
 18:30-19:00   -10.271   21hrs    15:30-16:00   -10.276     0.5         -10.274      0.2
 19:00-19:30   -10.277   21hrs    16:00-16:30   -10.278     0.1         -10.278     -0.2            “Truth” = -10.276
 19:30-20:00   -10.271   21hrs    16:30-17:00   -10.286     1.5         -10.279     -0.3
 20:00-20:30   -10.259   18hrs    14:00-14:30   -10.278     1.9         -10.269      0.7            Difference = 0.1 cm
 20:30-21:00   -10.254   18hrs    14:30-15:00   -10.295     4.1    *    -10.275      0.1
                                                                        "Truth"
 14:00-21:00   -10.275            14:00-21:00   -10.276     0.1         -10.276




                                                                                  NOAA, NOS, NGS
Comparison of 30 Minute Solutions - Precise Orbit; Hopfield (0); IONOFREE
(30 Minute solutions computed on the hour and the half hour)                                    Two Days/Same Time
                                                                                                 20.660 > 20.661
S132 to L132 7.9 Km                                                                              20.662
                                                        Day 264 *               Mean dh *        Difference = -0.2 cm
                 dh     Hours                    dh      minus diff   Mean dh    minus diff
 Day 264
                (m)      Diff.
                                 Day 265
                                                (m)     Day 265 >2      (m)      "Truth" >2      “Truth” = 20.615
                                                         (cm)   cm                (cm)   cm
                                                                                                 Difference = 4.6 cm
 14:00-14:30   20.599   27hrs    17:00-17:30   20.624    -2.5    *    20.612      -0.3
 14:30-15:00   20.610   27hrs    17:30-18:00   20.613    -0.3         20.612      -0.3
 15:00-15:30   20.613   27hrs    18:00-18:30   20.620    -0.7         20.617       0.2
 15:30-16:00   20.607   27hrs    18:30-19:00   20.611    -0.4         20.609      -0.5
                                                                                              Two Days/Different Times
 16:00-16:30   20.594   27hrs    19:00-19:30   20.615    -2.1    *    20.605      -1.0
 16:30-17:00   20.612   27hrs    19:30-20:00   20.619    -0.7         20.616       0.1
                                                                                                  20.660 > 20.637
 17:00-17:30   20.610   27hrs    20:00-20:30   20.662    -5.2    *    20.636       2.1   *         20.614
 17:30-18:00   20.615   27hrs    20:30-21:00   20.621    -0.6         20.618       0.3
 18:00-18:30   20.614   21hrs    15:00-15:30
                                                                                                  Difference = 4.6 cm
 18:30-19:00   20.608   21hrs    15:30-16:00   20.625    -1.7         20.617       0.2
 19:00-19:30   20.609   21hrs    16:00-16:30   20.601     0.8         20.605      -0.9            “Truth” = 20.615
 19:30-20:00   20.620   21hrs    16:30-17:00   20.628    -0.8         20.624       1.0            Difference = 2.3 cm
 20:00-20:30   20.660   18hrs    14:00-14:30   20.614     4.6    *    20.637       2.3   *
 20:30-21:00   20.618   18hrs    14:30-15:00   20.630    -1.2         20.624       0.9
                                                                      "Truth"
 14:00-21:00   20.609            14:00-21:00   20.620    -1.1         20.615




                                                                                NOAA, NOS, NGS
                                                                                             Two Days/Different Times
Comparison of 30 Minute Solutions - Precise Orbit; Hopfield (0); IONOFREE                        -9.184 > -9.185
(30 Minute solutions computed on the hour and the half hour)                                      -9.185
MOLA to YACH 12.9 Km                                                                             Difference = 0.1 cm

                                                        Day 264 *               Mean dh *
                                                                                                 “Truth” = -9.218
 Day 264
                 dh     Hours
                                 Day 265
                                                 dh      minus diff   Mean dh    minus diff      Difference = 3.3 cm
                (m)      Diff.                  (m)     Day 265 >2      (m)      "Truth" >2
                                                         (cm)   cm                (cm)   cm

 14:00-14:30
 14:30-15:00
 15:00-15:30
                                                                                               Need a Network!
 15:30-16:00
 16:00-16:30                                                                                  Line is greater than 10 km
 16:30-17:00
 17:00-17:30
 17:30-18:00
 18:00-18:30   -9.216   20hrs    14:00-14:30   -9.205
 18:30-19:00   -9.228   20hrs    14:30-15:00   -9.220    -0.8          -9.224     -0.6
 19:00-19:30   -9.219   20hrs    15:00-15:30   -9.193    -2.6          -9.206      1.2
 19:30-20:00   -9.203   20hrs    15:30-16:00   -9.208     0.5          -9.206      1.2
 20:00-20:30   -9.184   20hrs    16:00-16:30   -9.185     0.1          -9.185      3.3   *
 20:30-21:00   -9.210   20hrs    16:30-17:00   -9.186    -2.4    *     -9.198      2.0
                                                                      "Truth"
 18:00-21:00   -9.217            14:00-17:00   -9.218     0.1          -9.218




                                                                                NOAA, NOS, NGS
               Results from Pilot Project
• Base lines with high RMS produced outliers
• Base lines where integers could not be fixed produced outliers
• Standard deviation of a 30 minute session for short lines, i.e.
  less than 10 km, was 1.2 cm

• Standard deviation of the mean of two 30 minute occupations
  on two different days and different times of day was 0.8 cm

• Standard deviation of a 10 minute session for short lines, i.e.
  less than 10 km, was 1.7 cm
• Standard deviation of the mean of two 10 minute occupations
  on two different days and different times of day was 1.1 cm


                                         NOAA, NOS, NGS
         Establish / Monitor
          Project Control




CORS
       NOAA, NOS, NGS
NOAA, NOS, NGS
              Precision With CORS
• How GPS positioning is affected by baseline length

• Minimum occupation time required to meet
  established specifications
    Twice the rms @ ±2 cm for horizontal components
    Twice the rms @ ±4 cm for vertical components

      » Twice the rms being approximately equal to a 95%
        confidence region

• Varying length baselines formed from 19 CORS

• 10 days data from each site; various session lengths

                                    NOAA, NOS, NGS
                Design of Research

                  Sessions Processed

•   6 - 4 hour sessions  10 days  12 baselines = 720
•   4-6 “         “         “           “        = 480
•   3-8 “         “         “           “        = 360
•   2 - 12 “      “         “           “        = 240
•   1 -24 “       “         “           “        = 120
                     (Total # of Sessions)        1920




                                   NOAA, NOS, NGS
                        Processing
• One station constrained
• Second station computed
• ITRF97 (X, Y, and Z) @ epoch January 1, 1999
     X, Y, and Z position of second station is source of results
• Automatic integer fixing (on)
• Tropospheric model (on)
• Antenna phase patterns (ant_info.001)
• Precise ephemerides (NGS ephemeredes)



                                        NOAA, NOS, NGS
            North rms Relative to Distance
                           Mean rms - 10 Days of Observation
                 0.010
r m s N o r th




                 0.005




                 0.000
                      25    50    75    100 125 150 175 200 225 250 275 300
                                       Baseline Length (kilometers)

                         4 Hrs.        6 Hrs.       NOAA, 12 Hrs.NGS 24 Hrs
                                                 8 Hrs.   NOS,
                  East rms Relative to Distance
                         Mean rms - 10 Days of Observation

              0.010
rm s E a st




              0.005



              0.000
                   25   50   75   100 125 150 175 200 225 250 275 3
                                  Baseline Length (kilometers)


                         4 Hrs.      6 Hrs.   NOAA, NOS,Hrs.
                                              8 Hrs. 12 NGS      24 Hrs
             Up rms Relative to Distance
                     Mean rms - 10 Days of Observation
           0.030
rm s U p


           0.020


           0.010


           0.000
                25    50    75 100 125 150 175 200 225 250 275 300
                              Baseline Length (kilometers)

                   4 Hrs.     6 Hrs.       NOAA, 12 Hrs.NGS 24 Hrs
                                        8 Hrs.   NOS,
                                                                                                            4 Hr/160 K                                                                                                                                    6 Hr/160 K




                                                                                                                                                                                                   North Offset from 24 hr. Mean (m)
                                                     North Offset from 24 hr. Mean (m)
                                                                                         0.05                                                                                                                                          0.05

                                                                                         0.04                                                                                                                                          0.04

                                                                                         0.03                                                                                                                                          0.03

                                                                                         0.02                                                                                                                                          0.02

                                                                                         0.01                                                                                                                                          0.01

                                                                                         0.00                                                                                                                                          0.00

                                                                                         -0.01                                                                                                                                         -0.01

                                                                                         -0.02                                                                                                                                         -0.02

                                                                                         -0.03                                                                                                                                         -0.03

                                                                                         -0.04                                                                                                                                         -0.04

                                                                                         -0.05                                                                                                                                         -0.05
                                                                                             -0.05 -0.04 -0.03 -0.02 -0.01 0.00 0.01 0.02 0.03 0.04 0.05                                                                                   -0.05 -0.04 -0.03 -0.02 -0.01 0.00 0.01 0.02 0.03 0.04 0.05

                                                                                                                                     24 Hrs/160 K
                                                                        8 Hr/160 K 24 hr. Mean (m) 12 Hr/160East Offset from 24 hr. Mean (m)
                                                                           East Offset from                  K




                                                                                                                                                                                                                                                            North Offset from 24 hr. Mean (m)
North Offset from 24 hr. Mean (m)




                                    0.05                                                                                       North Offset from 24 hr. Mean (m)   0.05                                                                                                                         0.05

                                    0.04                                                                                                                           0.04                                                                                                                         0.04

                                    0.03                                                                                                                           0.03                                                                                                                         0.03

                                    0.02                                                                                                                           0.02                                                                                                                         0.02

                                    0.01                                                                                                                           0.01                                                                                                                         0.01

                                    0.00                                                                                                                           0.00                                                                                                                         0.00

                                    -0.01                                                                                                                          -0.01                                                                                                                        -0.01

                                    -0.02                                                                                                                          -0.02                                                                                                                        -0.02

                                    -0.03                                                                                                                          -0.03                                                                                                                        -0.03

                                    -0.04                                                                                                                          -0.04                                                                                                                        -0.04

                                    -0.05                                                                                                                          -0.05                                                           -0.05
                                        -0.05 -0.04 -0.03 -0.02 -0.01 0.00 0.01 0.02 0.03 0.04 0.05                                                                    -0.05 -0.04 -0.03 -0.02 -0.01 0.00 0.01 0.02 0.03 0.04 0.05     -0.05 -0.04 -0.03 -0.02 -0.01 0.00 0.01 0.02 0.03 0.04 0

                                            East Offset from 24 hr. Mean (m)                                           East Offset from (Horizontal) East Offset from 24 hr. Mean (m)
                                                                                                               Time Scatter Plots 24 hr. Mean (m)

                                                                                                                                                                                                                                                NOAA, NOS, NGS
                                                  Up Scatter @ 160 Kilometers

                                 0.060
Up Offset from 24 hr. Mean (m)




                                 0.040



                                 0.020



                                 0.000



                                 -0.020



                                 -0.040



                                 -0.060
                                          0   4    8       12     16      20       24
                                                  Observation Time in Hours

                                                                        NOAA, NOS, NGS
                   Up rms Relative to Time
                     Mean rms - 10 Days of Observation
rm s U p   0.03



           0.02



           0.01



           0.00
                     4 Hrs.          6 Hrs.           8 Hrs.       12 Hrs.     24 Hrs.
                                         Observation Time
                  26 k        57 k            101 k        127 k       153 k      160 k
                  201 k       252 k                   299 NOS, 300 k
                                              253 k NOAA,k     NGS
                 TABLE 2 - Multiple Session rms (21, 2
                                                   )
                                     Number of Sessions (n)
                                           North (n)
                 1           2           3             4         5           6
4 hour           0.010       0.007       0.006         0.005     0.004       0.004
6 hour           0.008       0.006       0.005         0.004
8 hour           0.006       0.004       0.004                                   Multiple Occupation
12 hour          0.005       0.004
24 hour          0.003                                                                Estimates
                                             East (e)
4 hour           0.010       0.007        0.006       0.005      0.005       0.004
6 hour           0.007       0.005        0.004       0.004
8 hour           0.006       0.004        0.004
12 hour          0.006       0.004
24 hour          0.004
                                             Up (u)
4 hour           0.036       0.026        0.021     0.018        0.016       0.015
6 hour           0.029       0.020        0.017     0.014
8 hour           0.027       0.019        0.015
12 hour          0.021       0.015
24 hour          0.016
                                                 2
1
  Table values are computed using the formula         where is the rms and n is the
                                                  n
number of sessions.
2
  All baseline distances are included in the computations of the rms of each session
lengths


                                                                     NOAA, NOS, NGS
NOAA, NOS, NGS
   Comments About Results With CORS Data
• Majority of time you are less than 300 km from
  CORS (continental U.S.)

• Baseline length has little effect on positional accuracy
    No setup error or antenna measurement blunders
    < 300 kilometers

    Using NGS’ PAGES software

    Precise ephemeris, Tropo models, and antenna patterns


• Horizontal and vertical specifications can be met in
  one 4-hour session


                                      NOAA, NOS, NGS
        Recommendations to Guidelines
            Based on These Tests

• Must repeat base lines
    Different days
    Different times of day

      » Detect, remove, reduce effects due to multipath and
        having almost the same satellite geometry

• Must FIX integers

• Base lines must have low RMS values, i.e., < 1.5 cm



                                     NOAA, NOS, NGS
NOAA Technical Memorandum NOS NGS-58                                                     Available On-Line at
GUIDELINES FOR ESTABLISHING GPS-DERIVED ELLIPSOID HEIGHTS
(STANDARDS: 2 CM AND 5 CM)
                                                                                          the NGS Web Site:
VERSION 4.3

                                                                                          www.ngs.noaa.gov
David B. Zilkoski
Joseph D. D'Onofrio
Stephen J. Frakes




Silver Spring, MD

November 1997




U.S. DEPARTMENT OF   National Oceanic and         National Ocean   National Geodetic
COMMERCE             Atmospheric Administration   Service          Survey




                                                                                       NOAA, NOS, NGS
       Station Selection and Reconnaissance
• Assure accurate connections to control stations
    NGS approved CORS
    TCORS (temporary or project CORS)

    HPGN / HARN

      » Federal Base Network (FBN)
      » Cooperative Base Network (CBN)
      » User Densified Network (UDN)
    NAVD 88 Bench Marks


• NGS Database and data sheets

• Identify GPS-usable stations

                                 NOAA, NOS, NGS
   NGS Internet Page
   www.ngs.noaa.gov




NOAA, NOS, NGS
NOAA, NOS, NGS
NOAA, NOS, NGS
NOAA, NOS, NGS
NOAA, NOS, NGS
NOAA, NOS, NGS
NOAA, NOS, NGS
                 Primary or Secondary
                Station Selection Criteria
1. HPGN / HARN either FBN or CBN
      Level ties to A or B stability bench marks during this project

2. Bench marks of A or B stability quality
      Or HPGN / HARN previously tied to A or B stability BMs

3. UDN stations
      Level ties to A or B stability bench marks during this project

4. Bench marks of C stability quality

• Special guidelines for areas of subsidence or uplift

                                          NOAA, NOS, NGS
             Four Basic Control Requirements

• BCR-1: Occupy stations with known NAVD 88 orthometric
  heights
      Stations should be evenly distributed throughout project

• BCR-2: Project areas less than 20 km on a side, surround project
  with NAVD 88 bench marks
      i.e., minimum number of stations is four; one in each corner of project

• BCR-3: Project areas greater than 20 km on a side, keep distances
  between GPS-occupied NAVD 88 bench marks to less than 20 km
• BCR-4: Projects located in mountainous regions, occupy bench
  marks at base and summit of mountains, even if distance is less
  than 20 km


                                                   NOAA, NOS, NGS
  Obstruction Visibility
       Diagram




NOAA, NOS, NGS
             Equipment Requirements
• Dual-frequency, full-wavelength GPS receivers
   Required for all observations greater than 10 km
   Preferred type for ALL observations regardless of length


• Geodetic quality antennas with ground planes
   Choke ring antennas; highly recommended
   Successfully modeled L1/L2 offsets and phase patterns

   Use identical antenna types if possible

   Corrections must be utilized by processing software
    when mixing antenna types




                                     NOAA, NOS, NGS
http://www.grdl/GRD/GPS/Projects/ANTCAL/index.shtml




                    NOAA, NOS, NGS
                                        Trimble Geodetic L1/L2 Antenna
                                        (TRM 22020.00)




Ashtech Geodetic III Antenna
U.S.C.G. V Antenna (ASH 700829.A1)




                                     NOAA, NOS, NGS
NOAA, NOS, NGS
NOAA, NOS, NGS
NOAA, NOS, NGS
NOAA, NOS, NGS
             Data Collection Parameters

• VDOP < 6 for 90% or longer of 30 minute session
    Shorter session lengths stay < 6 always
    Schedule travel during periods of higher VDOP


• Session lengths > 30 minutes collect 15 second data
      Session lengths < 30 minutes collect 5 second data

• Track satellites down to 10° elevation angle




                                        NOAA, NOS, NGS
                   Meteorological Data
• Weather data must be collected at control, primary,
  and secondary base stations at height of antenna PC
     Wet and dry temperatures, atmospheric pressure
       » Sessions > 2 hrs; record beginning, midpoint, ending
       » Sessions < 2 hrs > 30 min; record beginning and ending
       » Sessions < 30 min; record at midpoint

• Note on obs log where recorded and unusual conditions

• Stabilize equipment to ambient conditions

• Check equipment prior to observations


                                        NOAA, NOS, NGS
                   Antenna Setup
• Fixed-height tripods required for 2 cm standard
   Shade plumbing bubbles at least 3 min prior to plumbing
   Check perpendicularity of poles at beginning of project


• Fixed-height poles preferred for 5 cm standard
   Alternate tripod setups; antenna heights MUST be
    measured carefully and accurately
   Check measuring system before project
   Check and adjust tribrachs at beginning of project
   Perform totally independent meter and feet measurements
   Have measurement computations checked by someone else




                                    NOAA, NOS, NGS
   “Fixed” Height
       Tripod




NOAA, NOS, NGS
    “Slip-leg” Tripod

          and

      Slant Height
      Measurement




NOAA, NOS, NGS
                                    Table 1. -- Summary of Guidelines
    Table 1. -- Summary of Guidelines.

                                    Control              Primary Base           Primary Base          Secondary Base         Secondary Base          Local Network           Local Network
                                   2 and 5 cm                2 cm                   5 cm                   2 cm                   5 cm                    2 cm                   5 cm

     Dual Frequency             Yes, if base line is   Yes, if base line is   Yes, if base line is   Yes, if base line is   Yes, if base line is    Yes, if base line is    Yes, if base line is
        Required                greater than 10 km     greater than 10 km     greater than 10 km     greater than 10 km     greater than 10 km      greater than 10 km      greater than 10 km
      Geodetic Quality
    Antenna with Ground                 Yes                   Yes                    Yes                    Yes                    Yes                     Yes                     Yes
          Plane
      Min. Number of                                                                                       No                     No                      No                      No
                                         3                      3                     3
          Stations                                                                                       Minimum                Minimum                 Minimum                 Minimum

                                                                                                                     1                          1                       1                      1
      Occupation Time                5 Hours                5 Hours               5 Hours               30 Minutes             30 Minutes              30 Minutes             No Minimum

    Number of Days Station                                                                                       2                      2                       2                      2
                                         3                      3                     3                      2                      2                       2                      2
         Is Occupied
    Max. Distance Between
     Same or Higher-Order              75 km                 40 km                  50 km                   15 km                 20 km                   10 km                   20 km
           Stations
      Average Distance
                                   No Maximum            No Maximum             No Maximum             No Maximum             No Maximum                   7 km                   10 km
      Between Stations

           Repeat                             3                     3                      3                     3                          3                       3                      3
                                        YES                   YES                    YES                   YES                     YES                     YES                     YES
        "Base Line"

     Collect Met Data                   Yes                   Yes                    Yes                   Yes                     Yes                      No                      No


     Fixed Height Pole                  Yes                   Yes                     No                   Yes                      No                     Yes                      No


     Rubbing of Mark                    Yes                   Yes                    Yes                   Yes                     Yes                     Yes                     Yes


    Precise Ephemerides                 Yes                   Yes                    Yes                   Yes                     Yes                     Yes                     Yes

                                              4                     5                      5
       Fix Integers                     Yes                   Yes                    Yes                   Yes                     Yes                     Yes                     Yes

Notes for Table of Summary of Guidelines:
1
  Analyses have indicated that when following all guidelines in this document, 30 minutes of observations over base lines that are typically less than 10 kilometers will meet the standards.
For base lines greater than 10 km, but less than 15 km, 1 hour sessions should meet the standards. For observing sessions greater than 30 minutes, collect data at 15-second epoch interval.
For sessions less than 30 minutes, collect data at 5-second epoch interval. Track satellites down to at least 10-degree elevation cut-off.
2
  Base lines must be reobserved on different days with significantly different satellite geometry.
3
  The observing scheme requires that all adjacent stations have base lines observed at least twice on two different days with significantly different geometry.
4
  If base line is greater than 40 kilometers, a partially fixed or float solution is permitted.
5
  For all station pairs except those involved with control stations (see note 4
                                                                                                                     NOAA, NOS, NGS
Appendix B. - - GPS Ellipsoid Height Hierarchy

            HARN/Control Stations
                      (75 km)


                 Primary Base
                      (40 km)


                Secondary Base
                      (15 km)


               Local Network Stations
                    (7 to 10 km)




                                        NOAA, NOS, NGS
      HARN/Control Stations

                 CS1




CS2            75 km            CS3




                       NOAA, NOS, NGS
            Primary Base Stations
                      CS1
                     PB1




      PB2             40 km            PB3

CS2                                            CS3




                              NOAA, NOS, NGS
                    Primary Base Stations

• Basic Requirements:
      5 Hour Sessions / 3 Days

      Spacing between PBS cannot exceed 40 km

      Each PBS must be connected to at least its nearest PBS neighbor and
       nearest control station

      PBS must be traceable back to 2 control stations along independent
       paths; i.e., base lines PB1 - CS1 and PB1 - PB2 plus PB2 - CS2, or
       PB1 - CS1 and PB1 - PB3 plus PB3 - CS3




                                               NOAA, NOS, NGS
            Secondary Base Stations
                       CS1
                      PB1
            SB1                   SB2



            SB3       15 km       SB4


      PB2                               PB3

CS2                                             CS3




                               NOAA, NOS, NGS
                    Secondary Base Stations

• Basic Requirements:
      30 Minute Sessions / 2 Days /Different times of day

      Spacing between SBS (or between primary and SBS) cannot exceed 15 km

      All base stations (primary and secondary) must be connected to at least its 2
       nearest primary or secondary base station neighbors

      SBS must be traceable back to 2 PBS along independent paths; i.e., base lines
       SB1 - PB1 and SB1 - SB3 plus SB3 - PB2, or SB1 - PB1 and SB1 - SB4 plus
       SB4 - PB3

      SBS need not be established in surveys of small area extent




                                                     NOAA, NOS, NGS
             Local Network Stations
                        CS1
                       PB1
                      LN1
       SB1                            SB2
                LN2            LN3

        LN4                           LN5

                LN6    7 km    LN7

       SB3                            SB4
 PB2                                        PB3

CS2                                               CS3




                               NOAA, NOS, NGS
                       Local Network Stations

• Basic Requirements:
      30 Minute Sessions / 2 Days / Different times of the day

      Spacing between LNS (or between base stations and local network stations) cannot
       exceed 10 km

      All LNS must be connected to at least its two nearest neighbors

      LNS must be traceable back to 2 primary base stations along independent
       paths; i.e., base lines LN1 - PB1 and LN1 - LN2 plus LN2 - SB1 plus SB1 -
       SB3 plus SB3 - PB2, or LN1 - PB1 and LN1 - LN3 plus LN3 - SB2 plus SB2 -
       SB4 plus SB4 - PB3




                                                       NOAA, NOS, NGS
      Sample Project Showing Connections
                                                              CS2
CS1
                                                 LN4
             LN1                     LN3
                         LN2                           PB2
       PB1

             SB1               LN5         SB2




                               SB3


                                       SB5
                   SB4
       PB3                                             PB4


CS3                                                           CS4




                                             NOAA, NOS, NGS
Sample Project




             NOAA, NOS, NGS
             Project Information

• Area: East San Francisco Bay Project
   Latitude   37° 50” N to 38° 10” N
   Longitude 121° 45” W to 122° 25” W



• Receivers Available: 5

• Standards: 2 cm GPS-Derived Heights




                                NOAA, NOS, NGS
                             GPS-Usable Stations
38°20’N
               CORS
               HARN
               NAVD’88 BM
               New Station
               Spacing Station
               Primary Base Station




    122°35’W                          LONGITUDE                    121°40’W




                                                  NOAA, NOS, NGS
                               Primary Base Stations
38°20’N
               CORS
               HARN
               NAVD’88 BM                                  D191
               New Station               10CC

               Primary Base Station




                                                                  LAKE
                                                MART
                         MOLA




    122°35’W                           LONGITUDE                         121°40’W




                                                       NOAA, NOS, NGS
                                  East Bay Project Points
38°16’N
          CORS
          HARN                                    TIDD             D191
          NAVD’88 BM
          New Station             10LC
          Spacing Station
           Primary Base Station
                                                          MONT            X469        Z190
                                                                                                   DROU
                                          BM20
                                                                        Q555

                                         04KU
                                                                               CATT             TOLA
                                     TIDE          5144

                                          ZINC
                            PT14                                          R100
                                                                 P371
                                                                                                04HK

                                           MART                                          LAKE

    122°20’W                                        LONGITUDE                                     121°40’W




                                                                        NOAA, NOS, NGS
                                    Observation Sessions
38°16’N
          CORS          Session F
                                                             Session E
          HARN
          NAVD’88 BM                                                     Session D
          New Station
          Spacing Station
           Primary Base Station




                Session G




                  Session A
                                                                         Session C
                                                 Session B
    122°20’W                               LONGITUDE                          121°40’W




                                                         NOAA, NOS, NGS
                                  Independent Base Lines
38°16’N
          CORS
          HARN
          NAVD’88 BM
          New Station
          Spacing Station
           Primary Base Station




    122°20’W                              LONGITUDE                    121°40’W




                                                      NOAA, NOS, NGS
        Observation Schedule
Day   Session          Start Time   Stop Time
 1       A               8:00 AM     8:45 AM
 1       B               9:15 AM    10:00 AM
 1       C              10:30 AM    11:15 AM
 1       D              11:45 AM    12:30 PM
 1       E               1:00 PM     1:45 PM
 1       F               2:15 PM     3:00 PM
 1       G               3:30 PM     4:15 PM
 2       D               8:00 AM     8:45 AM
 2       E               9:15 AM    10:00 AM
 2       F              10:30 AM    11:15 AM
 2       G              11:45 AM    12:30 PM
 2       A               1:00 PM     1:45 PM
 2       B               2:15 PM     3:00 PM
 2       C               3:30 PM     4:15 PM




                       NOAA, NOS, NGS
                 Field Observations
• Observation logs
   Record complete receiver/antenna manufacturer, model part
    number, and serial numbers
   Record meteorological data and unusual conditions
   Record station and observer information
   Record height of antenna and measurement computations


• Obtain a clear station rubbing
   Rubbing for each occupation of station
   Make complete plan sketch of mark when rubbing not
    feasible




                                    NOAA, NOS, NGS
                        4-Char ID:           Station Name:                                                                                   Day of Year:              Date (UTC):
 GPS Station               BEAV                      BEAVER MARSH                                                                                 230                      08/18/98
   Observation
       Log              Location:                                                                                                            Observing Agency Full Name:
    (04-06-99)                       In Beaver Marsh, OR                                                                                     Nat ional Geodet ic Survey

Station PID:            Project Name:                                                                                                        Project Number:           Station SSN:
   PB0632                                Oregon FBN, 1998                                                                                    GPS- 1333                       0026

Station                       Latitude                                       Longitude                                Elevation (h) Information         Datum-Ellipsoid:        Session Obs.
Coords.                                                                                                                                                                            230 A
                 4308' 00.33708"                    N                  1 48' 1 91
                                                                         21     7.21 5"                   W      Ellipsoidal _1392.66 _ meters              NAD-83


Observing Period:
Scheduled Start (UTC) __1500 ___         Actual Start (UTC) ___1447____
                                                                                         Epoch Interval
                                                                                   15 Second ___ X__
                                                                                                                 Geoid (96) ___-21 _ _meters
                                                                                                                                  .41

                                                                                                                               41 58
                                                                                                                 Orthometric _1 4.1 _meters
                                                                                                                                                        Operator Name:
                                                                                                                                                                 Curt L. Smit h
                                                                                                                                                        Phone Number:
                                                                                                                                                                                               Sample Observation Log
Scheduled Start (UTC)   __2030 ___       Actual Stop (UTC)   ___2030 ____              30 Second _______                                                         503-986-3543

    TRACKING EQUIPMENT
                            Trimble 4000SSE
                                                                                       ANTENNA HEIGHT COMPUTATIONS
                                                                                                                                                                                                    (Front Side)
Receiver MFR & Model:                                                                      Slant/Vertical Height Measurements
Receiver S/N:       5A1
                 351 0453                                        Measurements Taken                                  Before                                          After
                                                                From/To Or Notch #                     (M)                       (FT)                    (M)                     (FT)
Reciver P/N:     18292-20

Antenna Manufacturer:    Trimble
                                                              Top of Mark t o #4                       1.286                     4.22                   1.286
Antenna Model:                   /L2
                       Compact L1 w/GP
                                                              Bottom of Ground Plane

Antenna S/N:             0220003686
                                                                          #8                           1.285                   1.286                   1.285
Antenna Part Number:     22020-00
Antenna Mounting Method: Fixed Height Pole (FHP)___
Fixed Mount: ____    Slip Leg Tripod: __ X _
                                          _                              #12                           1.285                                            1.285

Tripod/FHP Manufacturer: _Wild_____ S/N: _A_____              Mean Slant Height                       1.2853                                            1.2853
                         _
Tribrach: Wild GDF 22: _X Topcon: ____ None: ___
Trivet: ____ Other: ____ Calibration Date:08/08/98
                                                              Vertical Height to ARP                 1.2084                                             1.2084

Total Antenna Cable Length:                     0
                                             _ 1 _ (M)                                                                                            ***See Back of Form****

Antenna Plumb Check: Before? __Y__ After? __Y__               Height Entered Into Receiver: _____1.2084_____ (M)                  Be Very Explicit as to Where and How Measured

Eccentric Occupation? Y _____, N __X (if Y, see back)
                                    _                         Antenna Oriented True North? Yes _X No ____ if No, Explain
                                                                                                 _

                  POWER SOURCE
Camcorder Batteries:     ________                                                                             WEATHER DATA
External 12 Volt:             ____ X____                                      Time            Temperature Dry           Temperature Wet            Reletive                  Pressure
Commercial AC 110 Volt:       ________                                       (UTC)             (F)       (C)             (F)        (C)           Humidity%        (in Hg)              (Mb)
Barometer MFR/Model: __W  allace-Tiernan___
Serial Number: __WP-551 _ Units Read: __Ft ___
                       79                                     Before           1457           58.0            14.4      56.0         13.3           90.0           29.98           1 5.3
                                                                                                                                                                                    01

Obstructions>10 degrees above horizon? __Y__ (Y or N)         Middle           1745           78.0            25.6      68.0        20.0            58.0           30.00            01
                                                                                                                                                                                   1 6.0
Obstruction Survey Performed?
Yes: ____     No: ____     Performed Previously: _ _X_         After         2031             82.0            27.8      64.0         17.8           36.0           30.01           1 6.3
                                                                                                                                                                                    01
Other (explain):
                                                               Mean of Readings                               22.6                                   61.3                           01
                                                                                                                                                                                   1 5.9

Data File Name (Format: aaaaddds.nnn)                                                              5-Digit Weather Code (see reverse for codes)
      BEAV230A.DAT
                                                              Before:     02020                           Middle:          01
                                                                                                                         01 1                           After:     00102
aaaa=4-Char ID, ddd=julian day, s=session,
nnn=MFR or software dependent extension                       Weather Taken At Antenna Height? Yes: _ X No: ____ If Not Explain:
                                                                                                       _


Remarks (Comments on Problems, etc):
          *Not e* Dimple on disk is about 3 mm deep
              3
          SV 1 list ed as unhealt hy
          SV 24 Off/on due t o probable obst ruct ions
Note: Entries are Required in All Unshaded Areas.                       Vehicle is parked    10    meters      NE     (direction) from antenna.          Log Checked By:          JDD

                                                                                                                                                                                           NOAA, NOS, NGS
                                        GPS           OBSERVATION                      LOG
RADIO FREQUENCY INTERFERENCE: (Report any problems that may be caused by RFI. Give source and location if known.)

                          /4
Microwave ant enna about 1 mile east of st at ion. No apparent int erference not iced during session.

Station Rubbing or Photograph on Separate Sheet / Unusual Antenna Setups Illustrated on Separate Sheets if Necessary.

Views of Antenna Setup and All Measurements (include known specific antenna constants, radius, and phase center measurements):



                                                                                                                                                 Sample Observation Log
                                                                                                                                                      (Back Side)


Indicate the distances of the plumb point relative to the station    Slant height measurements are read from the station mark to the
mark= reference point if the horizontal eccentricity for the
      s                                                              following identifiable antenna feature, explain:
plumb point is greater than 0.5 mm.                                    Inside not ch, bot t om of ground plane.
                                                              TN     VERTICAL antenna height computations from the slant height


                                                             
                                                                     measurements (GP=ground plane; ARP=antenna reference point):

                                                                     Identify ARP =       Bot t om of ant enna pre-amp

               None Not ed                                             E (measured slant height) =        1.2853
                                                                       R (ground plane radius)         = 0.2334
                              +                                        C (constant; GP to ARP)         = -0.0556
                                                                                               _________
                                                                                               
                                                                        VERTICAL H.I. to ARP = ( E 5 - R 5 ) + C

                                                                     H.I. Computations to ARP                Feet/Meter Check
                                                                                                                      4.22              (M)
                                                                      .26
                                                                     1 396 + (-0.0556 )                                  
                                                                                                                    0.3048
                                                                         1.20836                (M)                1.286 3          (FT)
  CODE         PROBLEM            VISIBILITY        TEMPERATURE            CLOUD COVER               WIND            CONDITION = ENTRY

                                                        NORMAL                                                        N,G,W,CL,C    =   00000
                                    GOOD              (0 C TO 27C)            CLEAR                  CLAM             N,F,W,CL,C    =   01000
   0         NO PROBLEMS        (OVER 15 MILES)       (32F TO 80F)         (BELOW 20 %)          (UNDER 5 MPH)         Pr,P,W,C,M   =   12001
                                                                                                                       N,G,W,F,M    =   00200
                                                         HOT
               PROBLEM               FAIR             (OVER 27C)          PARTLY CLOUDY            MODERATE           N = NONE, P = POOR
   1         ENCOUNTERED         (7 MI - 15 MI)       (OVER 80F)            (20 % - 70 %)       (5 MPH - 15 MPH)      W = WARM, F = FAIR
                                                                                                                      G = GOOD, C = CALM
                                                         COLD                                                         M = MODERATE
                                   POOR               (BELOW 0 C)            OVERCAST               STRONG            Pr = PROBLEM
   2           NOT USED        (UNDER 7 MILES)       (BELOW 32 F)           (OVER 70 %)          (OVER 15 MPH)         CL = CLEAR
                                                                                                                                                NOAA, NOS, NGS
                  Rubbing of Survey Disk or Logo Cap

                    FBN/CBN Observations
Station Name:       OGILVIE                PID:        QC1049
                                                                       Sample Station Rubbing
Location:       At John Day Airport , OR   County:     Grant

Observer:       Curt is L. Smit h          Date:       8/26/98

Agency/Company:          NGS               Phone:    (503) 986-3543




Stamping:           OGILVIE 1989

Monument by Agency:      ORDT / NGS

Remarks: Oregon Primary GPS St at ion Disk in t op 35 cm round
concret e monument recessed 1cm
                                                                      NOAA, NOS, NGS
           Basic Concept of Guidelines
• Stations in local 3-dimensional network connected
  to NSRS to at least 5 cm uncertainty

• Stations within a local 3-dimensional network
  connected to each other to at least 2 cm uncertainty

• Stations established following guidelines are
  published to centimeters by NGS




                                   NOAA, NOS, NGS
Network / Local Accuracy




                 NOAA, NOS, NGS
                     Points of Contact

• National Geodetic Survey
  NOAA, N/NGS12
  Geodetic Services Division
  Bldg. SSMC3, Station 9202      • Curtis L. Smith
  1315 East-West Highway           Phone: 208-332-7197
  Silver Spring, MD 20910-3282     E-mail: Curt.Smith@noaa.gov
  Phone: 301-713-3242
  Fax: 301-713-4171

• Internet Web Site:
    www.ngs.noaa.gov




                                        NOAA, NOS, NGS

								
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