differential pseudorange solution is generally found to be in the range of 0.5 to 10 meters. These
accuracies are largely dependent on the type of GPS receiver used.
b. Carrier beat phase formulations can be based on the L1, the L2, or both carrier signals.
Accuracies achievable using the carrier beat phase measurement are generally accepted to be 1 percent
of the wavelength. Using the L1 frequency where the wavelength is around 19 centimeters, the
theoretical resultant range measurement is 1 percent of 19 centimeters (about 2 millimeters). The L2
carrier can only be used with receivers that employ cross correlation, squaring, or another technique to
get around the effects of AS.
PART D - PLANNING PRECISE-POSITIONING SURVEYS
5-29. General. Using differential carrier phase surveying to establish control for military projects
requires operational and procedural specifications for a project-specific function of the control being
established. To accomplish these surveys in the most efficient and cost-effective manner and to ensure
that the required accuracy criteria are obtained, a detailed survey-planning phase is essential. This
section defines global positioning system-survey (GPS-S) design criteria and other specifications that
are required to establish control for survey projects.
5-30. Planning a Control Survey. The first step in planning a control survey is to determine the
ultimate accuracy requirements. Survey accuracy requirements are a direct function of the project's
functional needs--the basic requirements needed to support the planning, engineering design,
maintenance, and operations. This is true for GPS or conventional surveying in order to establish
project control. Most military activities require relative accuracies (accuracies between adjacent control
points) ranging from 1:1,000 to 1:50,000, depending on the nature and scope of the project. Few
topographic projects demand positional accuracies higher than the 1:50,000 level (second-order, Class
I). Although a GPS-S may be designed and performed to support lower-accuracy project-control
requirements, the actual results could generally be several magnitudes better than the requirement.
Although higher accuracy levels are easily achievable with GPS, it is important to consider the ultimate
use of the control on the project in planning and designing GPS control networks. Thus, GPS-S
adequacy evaluations should be based on the project's accuracy standards, not those theoretically
obtainable with GPS.
a. Project Functional Requirements. Project functional requirements must include planned and
future design and mapping activities. Control density within a given project is determined from factors
such as planned construction, site plan mapping scales, master plan mapping scales, and
artillery/aviation survey positioning requirements. The relative accuracy for project control is also
determined based on such things as mapping scales, design needs, and project types.
b. Project Control Surveys. Project control surveys should be planned, designed, and executed to
achieve the minimum accuracy demanded of the project's functional requirements. To most efficiently
use resources, control surveys should
5-15
EN0593
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