water can impede leveling operations. Signals from the GPS constellation generally require a clear line
of sight to the sky. Urban and forested areas can mask or deflect the direct signal needed for accurate
measurements. Good reconnaissance and proper planning can alert the field parties of the best times and
methods to use.
experience level of the assigned personnel. The most effective method for training personnel is under
real training conditions.
Modern, well-maintained equipment can often increase the rate of progress. Older equipment, if
properly maintained or adjusted, will yield accurate results. Having to stop to repair or replace broken
instruments or parts can result in a slowdown or halt a field survey. All equipment should be calibrated
during combat checks, before survey missions.
2-17. Survey Purpose. The purpose and the type of survey determine the accuracy requirements, and
the accuracy requirements dictate both the equipment and the techniques used. For instance,
comparatively rough techniques can be used for elevations in site surveys, but control-network leveling
requires much more precise and expensive equipment and extensive, time-consuming techniques. First-
order GPS, triangulation, traverse, or leveling for the control networks must have high-accuracy
standards; cuts and fills for highways are much lower. In some surveys, distances to inaccessible points
must be determined. High-accuracy distance and angle measurements are required so that these values,
when used in trigonometric formulas, will yield acceptable results. This type of survey is directly
dependent on the clearness of the atmosphere. Observing measurements for a single position can be
delayed for days while waiting on good weather.
2-18. Errors. All measurements contain errors. Errors classified as systematic and accidental are the
most common uncontrollable errors. Besides errors, measurements are susceptible to mistakes that arise
from misunderstanding problems, poor judgment, confusion, or carelessness. The overall effect of
mistakes can be greatly reduced by following a preestablished systematic procedure. This procedure is
advantageous in all phases of a survey.
2-19. Progress. Rates of progress vary, depending on personnel experience and repetition. As skill and
confidence increase, so will speed. Proper preparation and planning will reduce duplication of effort
and increase efficiency.
2-20. Enemy. A hostile environment often forces a schedule adjustment. Night work requires greater
speed, fewer lights, and increased security. Adding security forces increases the number of vehicles and
personnel, which reduces efficiency and retards the time schedule.
2-21. Observations of Distances and Directions. Topographic surveyors observe distances and
directions (angles) to establish the following:
EN0593
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