Radar pointing down by QoA2W6h7

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									Radars Pointing
    Rivers
Water Surface Velocity
          &
     Bed Profiling
    OUTLOOK
   Following monitoring practice in ocean and
    atmosphere  river monitoring moves toward
    remote sensing practices
   USGS has put forth a team (Hydro 21) for remote,
    non-contact, river monitoring to replace the over
    7,000 stream gages
   Remote sensing might revolutionize the current
    multi-task (discharge – velocity – depth - slope)
    river monitoring practice
   Intensive and extensive developments needed to
    overcome practical implementation
 MEASUREMENT CANDIDATES
  Wave-based techniques: electromagnetic radiation
   and sound (magnetic and pressure waves): radars,
   image velocimetry, sonars




http://www.geocities.com/kbachhuber2000/ems.html

http://imagine.gsfc.nasa.gov/docs/science/know_l1/emspectrum.html
RADARS

   Most extensive tested so far for riverine
    environment
   Wavelenghts from microwaves to radio waves
   Doppler (coherent) or non-Doppler systems
   Various configurations
   Measurement objectives:
    – free-surface velocities
    – bathymetry
    – stage
    OPERATING PRINCIPLE
Velocity: Bragg scattering

Issues:
                                                      
- what represents v?
                                                          f
- how to relate v to velocity                    f'
  in the water column?
                                                                     v
- how to get the proper free-
  surface wavelength (only      v = fd / (2 cos), (f d = f-f')
  one detected for a given           v : water velocity
  radar wavelength)                  : wave length
                                     fd : Doppler frequency


                                                                   KOWACO
   OPERATING PRINCIPLE
Configurations: Monostatic (same antenna for emission
  and reception)
- Scanning strategy
- Assumptions:
  - Velocity constant over spot
  - Streamwise direction known
  OPERATING PRINCIPLE
Configurations: Bistatic (distinct antennas)
 RADARS: PROs & CONs


         PROs                              CONs
Analytical support        Directional velocity measurement
Independent of lighting   Local (point) measurement
Visual output             Signal (not intuitive) as output
                          See issues
                          Measurements F(λ, Λ, geometry)
                          Cost
     OPERATING PRINCIPLE
Ground Penetrating Radar (GPR)
  for Bathymetry: reflection of
  pulsed high-frequency
  electromagnetic waves

Issues:
-   Site specific f(surface and
    subsurface permittivity)
-   Performance f(speed of sound in
    the measured media, reflectivity,
    depth of investigation, resolution,
    interferences, calibration)
                                          http://fate.clu-in.org/gpr.asp?techtypeid=41
GP RADARS: PROs & CONs



            PROs                        CONs
Analytical basis             Complex signal processing
Unique for such measurements See issues
Visual output                Cost
SELECTED RADAR
CONFIGURATIONS & MEASUREMENTS



 Microwave Water Surface Current Meter (KOWACO)
 UHF RiverSonde Radar (CODAR)
 Ground Penetrating Radars (MALA GeoScience AB)
 Flo-Dar (Marsh-McBirney Inc.) DEMO
Microwave Water Surface Current
Meter (MWSCM-KOWACO)
MWSCM SPECIFICATIONS
   Detection Method :
    Microwave, Doppler effect
   Frequency : 10 GHz
   Measurement Range : 0.5~10m/s
   Measurement Angle :
    –   Vertical : 20 ~ 45°
    –   Horizontal : 0 ~ 10°
   Weight
    –   Antenna : 4.9Kg, Signal processor : 4.2Kg
   MWSCM VERIFICATION
Korea Institute of Construction Technology
                                                  5




                                                  4




                        Measured velocity (m/s)
                                                  3




                                                  2

                                                                             Velocity Comparison

                                                                                   Vertical angle : 20 deg.

                                                  1                                Vertical angle : 30 deg.

                                                                                   Vertical angle : 40 deg.

                                                                                   Vertical angle : 45 deg.

                                                  0

                                                      0   1       2            3               4              5
                                                              Carridge velocity (m/s)
MWSCM MEASUREMENTS
Daechung Dam                           4




                                       3




                     Velocity (m/s)
                                       2




                                                              Taechung Dam

                                                              2433 m^3/s(EL. 31.40M)
                                       1
                                                              1960 m^3/s(EL. 30.90M)

                                                              1593 m^3/s(EL. 30.24M)

                                                              999 m^3/s(EL. 29.42M)

                                       0
               Elevation (m)




                                      30




                                      20

                                           0   40   80        120        160           200
                                                    Distance (m)
   RIVERSONDE RADAR
Transmitter




Receiver




                Barrick et al. (2003)
GPR
USGS Measurements with MALA GPR




                         Haeni et al. (2003)
DEMO
FLO-DAR (Marsh-McBirney Inc.)
Doppler 24 GHz radar




http://www.marsh-mcbirney.com/classes/flo-dar_technology/
DEMO
FLO-DAR (Marsh-McBirney Inc.)
Instrument control: FFT of the Doppler shift




   Output: channel discharge
 VALIDATION
 FLO-DAR (Marsh-McBirney Inc.)
                                                                               SP
                                                                                V
                                                                               LI
                                                           4c
                                                           2m
        iu
        qd
        Li                                                                9c
                                                                          7m
         o
         a
        Sp
                                   u e
                                    b
                                    b
                                   B lr
                                                                           L D
                                                                            O R
                                                                           F - A
                                                  a
                                                  Fn
                    o
                    Fm
                     a                                         . m
                                                              6c
                                                              17

                                                                   u e
                                                                    b
                                                                    b
                                                                   B ls        c
                                                                               1m
             0c
             1m
                                                                                 D
                                                                                 L



1.   Best measurements: continuous foam layer (errors up to 10 %)
2.   Good results: floating particles (2-3 mm diameter)
3.   Poor results: controlled waves (errors up to 40%)
4.   Not reliable: natural free surface waviness and lower than 0.5 m/s

								
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