CSI Wireless GBX, Reference Manual

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GBX Reference Manual 3
1.2.2 Real-Time DGPS
The base station transmits the range error corrections to remote
receivers in real-time. The remote receiver corrects its satellite range
measurements using these differential corrections, yielding a much
more accurate position. This is the predominant DGPS strategy used
for a majority of real-time applications. Positioning using corrections
generated by DGPS radiobeacons will provide a horizontal accuracy of
1 to 5 meters with a 95% confidence. More sophisticated, short-range
DGPS systems (10 to 15 km) can achieve centimeter-level accuracy,
but are very expensive and often limited to precise survey applications
due to technical constraints on their use.
1.3 DGPS Format
For manufacturers of GPS equipment, commonality is essential to
maximize the utility and compatibility of a product. The governing
standard associated with GPS is the Interface Control Document, ICD-
GPS-200, maintained by the US DoD. This document provides the
message and signal structure information required to access GPS.
Like GPS, DGPS data and broadcast standards exist to ensure
compatibility between DGPS networks, and associated hardware and
software. The Radio Technical Commission for Maritime Services
Special Committee 104 has developed the primary DGPS standard
associated with radiobeacon DGPS, designated RTCM SC-104 V2.2.
Various broadcast standards may exist for the beacon networks
installed internationally, controlled by their respective operating
authority. The United States Coast Guard maintains a broadcast
standard that is referenced in the Further Reading section of this
manual.