Lecture 02 Topo Maps UTMs Compass

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Lecture 02 Topo Maps UTMs Compass Powered By Docstoc
     360º make a circle
 (earth is divided into 360º)

Degrees are divided up into 60
     smaller units called:


 Each minute is spilt into 60
        parts called:


                                 NASA Image
                 To precisely locate points on the earth,
degrees latitude and longitude have been divided into minutes and seconds

        (e.g., Lat:38º53’23”N; Long:77º00’27”W       U.S. Capitol
      Lat: 46° 52' 19.7" N, Long: 113° 59' 38.4" W   Missoula, MT)

                       Parallels                                Meridians

                  Missoula, MT
  Lat: 46° 52' 19.7" N, Long: 113° 59' 38.4" W

Great…but what about the realities of declination?
Magnetic declination = the difference between true north (the geographic North
                       Pole) and magnetic north (the north that your compass
                      points to).

                             True North Pole (star symbol)
                             The geographic North Pole; the axis around which earth rotates

                             Magnetic North Pole (MN)
                             The north that your compass points to

                             Grid North (GN)
                             The direction of reference lines shown on the map
Magnetic declination = the ANGLE between True North
and Magnetic North.

* The amount of declination at any given point depends on the location
of that point on the continent.

•Where true and magnetic north are in the same direction, the
declination is ZERO.

* In North America, a line of zero declination runs from just west of
Hudson Bay, down along Lake Michigan, to the Gulf Coast in western
Florida. At any point EAST of that zero line, a compass needle will
point west of True North (called “westerly declination); in North
America, magnetic declination varies from 30° east in AK to 30° west
in Labrador.
                                           Missoula’s current
                                          Magnetic declination:
                                            14° 13' EAST

            For online declination adjustments:
A compass consists of a magnetized pointer that aligns itself accurately with
Earth's magnetic field. A compass provides a known reference direction which is of
great assistance in navigation. The cardinal points are north (0°), south (180°), east
(90°), and west (270°).

  The composition of the earth
  acts as a bar magnet sitting
  upside down in the middle of the
  planet. Since its South end is at
  the north pole and its North end
  is at the south pole, the North
  end of a compass needle is
  pulled north.
         PACE = 1 natural step

PACE = # of meters or feet / # of steps

(e.g., 100 feet/25 steps = 4 feet per step)

                                              Wright Brothers
Scale = the relationship between distance on the map
and distance on the ground.

   Large scale maps
   Cover large areas

   1 inch = 8 miles

   1 inch = 4 miles
     Small scale maps
Show details, smaller areas

   1 inch = 2,000 feet

      1 inch on map =
24k inches in the real world
Most USGS topographic maps use brown contours to show the shape and elevation of
the terrain. Contour intervals vary, depending on the terrain and the scale of the map.

National Parks Digital Guide Tour (Maptech)
                            This grid layout has roots in
                                 horseback survey…

  Union Peak Quadrangle,
T13N R14W , NW Section 33
     7.5 Minute Series,
       Revised 1965
   (Declination 19 1/2°)
                   John Wesley Powell

          1869 Explored the Grand Canyon
1881-1884 U.S. Geological Survey Director

The People of the American West met John Wesley Powell’s expeditions across the American West; Powell insisted on an initial
survey before entry into the West (beyond the 100th meridian), which inadvertently suspended things like the Homestead Act of
1862. Photo courtesy of the Smithsonian Institution; students of Powell on 1868 expedition; painting Down the Colorado by N.
Eggenhofer (1960).
  Public lands of the western U.S. were surveyed & divided into townships and
  ranges, according to the U.S. Rectangular System. Similar to latitude and
  longitude, townships and ranges measure a land area from north to south
  (township) and east to west (range).

             T2S R3W
lies in the 2nd township south of a
particular baseline & the 3nd range
west of a particular principal

Standard township: 6 miles square                                    Range

Township divided into 36 sections of
1 square mile each (640 acres)
Township of 36 sections, each 1 square mile (640 acres)

Standard township:
6 miles square
 Early surveyors established section corners
                       numbered sections

The U.S. Geological and Geophysical Survey of the Territories, 1871, National Archives & Records Administration
     Find the tiny red
  cross/plus sign on this
    topographic map.

   It refers to a section
  corner marker and the
      elevation at that
    particular location.

Sometimes corner markers consist
of a poured concrete monument
with a brass cap; and sometimes
they consist of a wood post in a
pile of rock (e.g., areas not
surveyed since the early 20th
                                   NW Missoula Quadrangle, Revised 1999
 Also, keep an eye out for benchmarks
(references points used in surveying, with
     known locations and elevations).

These are often noted on topographic maps
             with a black “X.”

  You should be able to locate them on the
 ground by searching for a brass cap with an
             elevation number
  (e.g., “2296” which denotes 2296 ft amsl)

                                               Mauna Kea Benchmark, HI; CSUS Archives
How do we get more precise than a 640-acre section for our site forms?

  T40N, R8W Section 7      SE ¼ of the SE ¼ of the SE (SE SE SE)

                                 NW               NE

                                 SW               SE
                  (Universal Transverse Mercator)
              The earth is divided into 60 Zones. Each zone is 6° wide.
Each zone is numbered beginning at the 180° meridian near the International Date Line.
Each zone divided into 1000-meter (1 km) units.
Tick marks along the side of 7.5. minute topo maps represent 1 km within those 1000-m units
                          Any point in a zone can be
                            referenced by citing:
                         1. its zone number;
                         2. its distance in meters from
Zone 11 Zone 12
                         the equator (northing); and
                         3. its distance in meters from
                         a N-S reference line (easting)
                         in each zone; that line is the
                         meridian/longitude line
                         bisecting each UTM zone.

        114° longitude
  NAD 27? NAD 83?
  The North American Datum = official datum used for the primary geodetic network in
  North America. In the fields of cartography and land-use there are currently two North
  American Datums in use: the North American Datum of 1927 (NAD27) and the North
  American Datum of 1983 (NAD83). Both are geodetic reference systems, but each is
  based on different measurements.
  While most USGS topographic maps use the 1927 North American Datum (NAD 27), maps
  are being slowly revised to NAD 83.
                                             Because Earth deviates significantly from a perfect
                                             ellipsoid, the ellipsoid that best approximates its
                                             shape varies region by region across the world. NAD
NAD 1927 is based on the                     1927 best suited North America as a whole. Likewise,
Clarke Ellipsoid of 1866; it                 historically most regions of the world used ellipsoids
was created by manual                        measured locally to best suit the earth's shape those
surveying of the entire
continent. The geodetic                      As satellite geodesy and remote sensing technology
"center" of NAD27 is a base                  reached high precision and were made available
                                             for civilian applications, it became feasible to
station at Meades Ranch                      acquire information referred to a single global
in Kansas.                                   ellipsoid. This is because satellites naturally deal with
                                             Earth as a monolithic body. Therefore the GRS 80
                                             ellipsoid was developed for best approximating the
                                             earth as a whole, and it became the foundation for
                                             the North American Datum of 1983. Though
                                             generally GRS 80 and its close relative WGS 84 are
                                             not the best fit for any given region, a need for the
                                             closest fit largely evaporates when a global survey is
                                             combined with computers, databases, and software
                                             able to compensate for local conditions…

                                         DATUM = a fixed reference point which measurements are taken.
NAD 27 base station at Meades Ranch in
Kansas. located at 39°13′26.71218″N
                 / 39.2240867167°N       Geodetic = scientific discipline that deals with the measurement and
98.5421516778°W39.2240867167; -
                 /                       representation of the Earth, including its gravitational field, in a three-dimensional time-
98.5421516778 (39.224087, -98.542152,
NAD83).                                  varying space
             National Register Bulletin 28:
  Using the UTM Grid System to Record Historic Sites

                           1. Draw a line from the top of the topo to
                           the bottom, connecting UTM tick marks
                           immediately to the west of the point.
                           2. Draw a line from the left to the right,
                           connecting UTM ticks marks immediately
                           to the south of the point.
                           3. Align the counter so that the side of the
                           scale that reads from right to left lies
                           along the east-west line and the side that
                           reads from left to right passes thru the
                           4. Read the coordinate counter scale:
                           right to left for easting & up for northing.

                          NOTE: easting values increase going east;
                          northing values increase going north

303 (303,000)   305
What if a site spans more than 10 acres?

                       Garnet Ghost Town, c. 1860s-1912 (1940s), Monte Dolack 2004
Label points clockwise starting from NE point
REDUCE extraneous area around complex site boundaries
           The UTM references for Garnet are:
                         Zone 12
               A 322405m E, 5187765m N;
               B 321000m E, 5187771m N;
               C 321702m E, 51886650m N;
               D 322425m E, 5188605m N.

The legals are: E3/4 of Section 3 and the W1/4 of Section 2
There’s always GPS…
“No matter what discovery or sampling techniques are
used, the spatial location of the archaeological remains
must be RECORDED…
…discovery and geographical location are the essential
aspects of reconnaissance”

                                    (Sharer and Ashmore 2003:242)

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