Taken from "Nebraska Geographic Information Systems Steering Committee - Gis Technical Standards" December 15, 1993, version.
Chapter 5. GPS Data Capture Standards
Role of GPS
(Obj 4 Task 1 - Promote integration of GPS with GIS by recommendation and adoption of appropriate standards)
Global Positioning System (GPS) surveying is an emerging technology that can significantly reduce the cost of both surveys and establishing extremely accurate map controls. A GPS system uses the transmissions from navigational satellites to triangulate and calculate x and y coordinates and elevation of a surveyed point. Although there are not enough satellites currently in orbit to cover all areas in the United States at all times, we are reaching a level of saturation of satellites that will permit 24 hour visibility in most areas for GPS activity.
Due to the intentional degradation of satellite signals by the military, single GPS units are unable to gain accurate positional fixes. However, if accuracy within a few centimeters rather than tens of meters is needed, additional GPS units can be used. One unit is located on a known location and, through differential processing, the location of the other units can be corrected and determined to much greater accuracy. For real time coordinate accuracy, a base unit can be established and, using radios, transmit its location to other units so that their location can be determined relative to the base station.
Recommendation:
The US National Geodetic Survey is developing a High Accuracy Reference Network (HARN) using GPS, which the State of Nebraska should compliment in its GPS development.
