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Desert Pumping Project. Meetings on using the APTS to profile the Great
salt Lake Desert began in January 1985, and an agreement for the project
was signed on April 15, 1985.
DESIGN OF THE PROFILING SURVEY
The transition from the APTS application testing program to the Salt Lake
Desert Profiling Project was significant and offered a considerable chal-
lenge. Several factors about the new project are important:
e The size of the project, 40 x 40 miles, was much larger than any
previous project. Whereas the previous projects required only a
few hours of flying to obtain the profile data, the Salt Lake
Desert Profiling Project would require 30-50 hours of flying.
® All the previous surveys were in eastern Massachusetts with cool
temperatures, elevations near sea level, moderate topographic
relief, many lakes and rivers, and thick stands of timber. With
respect to all of these environmental factors, the Salt Lake
Desert Project presented extremely contrasting conditions.
The selection of retroreflector sites was influenced by the location of
existing elevation control. Fortunately, control elevations of sufficient
accuracy were available at many points within the project area. Most were
the result of USGS map control surveys made in 1973 when elevations were
established at many of the township corners. Elevations also were
recently established in the remote regions of the desert by Caldwell,
Richards, and Sorensen Engineers under contract to the Utah Department of
Natural Resources. This fortunate coincidence of the desired retro-
reflector spacing matching the distance between township corners (6 miles
or about 3 minutes of flying time) was utilized, and the retroreflectors
were generally positioned at township corners (fig. 2). Profile flight-
lines were planned in a crisscrossing pattern such that profiles were
obtained between all adjacent retroreflectors. This profile pattern
agreed well with an earlier estimate that profiles not be separated by
more than 2 miles in order to capture sufficient topographic detail in the
mud-flat type desert country.
The project was divided into seven flight mission areas (fig. 3). Small
areas were necessary because of the limited number of retroreflectors
available (28) and because the aircraft flight time is limited to about
2 1/2 hours due to the amount of fuel that can be carried. The two flight
missions for area C are given in figures 4 and 5. The first flight pro-
duced the diagonal profiles and the second produced the profiles in the
cardinal directions. Both areas B and C were covered by the flightline
shown in figure 5.
RETROREFLECTOR SITE SURVEYS
The ground survey work began in late May 1985 with a USGS field party
operating from Wendover, Utah. A Bell Ranger helicopter was made avail-
able to provide transportation into the remote regions of the project. At
that time of year, most of the Great Salt Lake Desert is inaccessible by
ground travel due to excessive moisture, which forms a thin surface layer
of slick mud.
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