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STATIC AND KINEMATIC GPS SURVEYS
GPS ground surveys that have centimeter-scale horizontal and vertical
accuracy serve to calibrate and evaluate the accuracy of airborne surveys
and to bring various topographic data, such as beach profiles measured
with electronic total stations, into a common reference frame. Kinematic
vehicle surveys also provide high-accuracy topographic data of beaches.
image to enlarge
Static geodetic GPS surveys, real-time differential GPS surveying
and navigation, and surveying by means of electronic total stations.
2. Kinematic GPS surveys of beached for coastal research.
3. This figure shows the distribution of elevation measurements
along a 100 meter length of beach at Galveston Island State
Park. The blue circles (o) are data points from a kinematic
GPS vehicle survey conducted on 1 May 1995. The position and
elevation of a GPS antenna mounted on a 4x4 vehicle was measured
twice per second as the vehicle made seven passes along the
beach. The red crosses (+) are
laser ground points collected during two aircraft passes on
6 August 1998. The airborne laser operated at 5000 pulses per
second and scanned a swath approximately 350 m wide. A two-meter
grid is superimposed on this map view to illustrate the data
density possible with airborne laser terrain mapping (ALTM).
Three-dimensional surfaces of the beach constructed from the vehicle
and ALTM elevation data. The horizontal blue lines represent 10-cm
contour intervals and the bold, red line is the -27.2 m height
above the WGS84 reference ellipsoid. The vertical exaggeration
is 2.4x. The kinematic GPS vehicle survey has an RMS of about
1 cm and the resulting surface is precise enough to reveal subtle
features such as beach cusps. These ALTM data have an estimated
RMS of 9 cm and the beach surface derived from laser mapping is
subsequently rougher. Nevertheless it is still easy to distinguish
the major features of the coast such as the foredune, berm, and
beachface. The obvious advantage of ALTM is the data continuity
across the beach and back barrier area. The advantage of the kinematic
vehicle survey is the superior accuracy capable of measuring subtle
rhythmic features along tens of kilometers of beach.
more information, please contact Jeff Paine