The collection of terrain and climatic information.
Arrangements for access to private or government property.
The availability of billeting, mess, medical, maintenance, and other required support.
2-40. Global Positioning System. Interreceiver visibility is not required for GPS surveying. Stations
can be set according to network design principles rather than traversing around buildings or mountains.
The only requirement for receiving GPS signals is a clear view of the sky. Choose a station with no
obstructions above an incline of 15, to 20,. Draw a station-obstruction diagram to assist in the planning
of GPS sessions. Verify the station accessibility, draw maps with directions to the stations, and mark
each station clearly. The field crew will be in a hurry to set up when they arrive, and unmarked stations
can waste valuable time.
2-41. Triangulation. When the need to locate the position of a point that cannot be occupied arises, as
in a special survey, triangulation is necessary. This technique makes special demands on the
reconnaissance party. The mathematical computations place stringent requirements on the size and
shape of the geometric figures that are used to determine coordinates. For this reason, the location of the
stations will normally be dictated to the field-reconnaissance party, based on the results of the office
reconnaissance. The reconnaissance party must ensure that the observation stations, which form the
baseline, are intervisible. A thorough knowledge of triangulation criteria is absolutely necessary.
2-42. Traverse. The demands for
a traverse reconnaissance are less stringent than for triangulation.
Ensure that both the rear and forward stations are visible from each proposed station. Wherever
possible, distances between stations should be uniform. In control surveys that may become part of the
United States National Control Network, the Standards and Specifications for Geodetic Control
Networks (SSGCN) must be satisfied. Spacing between stations is dependent on the available EDME.
2-43. Electronic Distance-Measuring Equipment. An EDME traverse reconnaissance requires
intervisibility between stations. The minimum and maximum allowable distances are based on the
EDME characteristics and the clearance above possible obstructions. Use of infrared EDME is
dependent on the weather.
2-44. Differential Leveling. Differential leveling should follow routes containing the
change in elevation between BMs and individual setups. The routes frequently follow roads with
moderate traffic, so care must be taken to ensure the safety of the leveling party.
2-45. Trigonometric Leveling. Trigonometric-leveling
reconnaissance is performed during
reconnaissance. If possible, select a relatively level area