What is DGPS?
Differential GPS (DGPS) is the regular Global Positioning
System (GPS) with an additional correction (differential)
signal added. This correction signal improves the accuracy
of the GPS and can be broadcast over any authorized communication
channel.
How does DGPS work?
The GPS determined position of a reference station is computed
and compared to its surveyed geodetic position. The differential
information ... some systems use the error in fix position,
while others use individual satellite range errors ... is
transmitted to user receivers by radio or other means.
Why use DGPS?
DGPS accuracy and integrity are better than GPS.
* Accuracy improvement (2drms): Positions of 10 meters or
better are achievable using DGPS (USCG signals) vs. 100 meters
or better for GPS (Standard Positioning Service)
* Integrity improvement: Provides an independent check of
each GPS satellite's signal, and reports whether it's good
or bad.
Where do I get Radiotechnical Commission Maritime Services
(RTCM) documents?
The Coast Guard does not provide RTCM documents. You can
order them directly from the RTCM
website or via mail. All orders must identify specific
documents being ordered and number of copies.
How is DGPS used?
DGPS receivers collect navigational signals from all GPS
satellites in view, plus differential corrections from a nearby
DGPS site. (Many DGPS receivers consist of two units: a GPS
receiver, with a data "port" for DGPS corrections,
directly connected to a radio receiver.) DGPS receivers display
position, velocity, time, etc., as needed for their marine,
terrestrial, or aeronautical applications.
What are the Coast Guard's plans
for DGPS?
The Coast Guard is developing a DGPS service for public use
in harbor entrance and approach (formerly harbor and harbor
entrance) areas of the continental United States, the Great
Lakes, Puerto Rico, and portions of Alaska and Hawaii. The
DGPS signals will be broadcast via USCG marine radiobeacons.
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