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DSM 132/132RS Receiver User Guide 21
Overview 2
23.3 Position Output
Geographic data obtained from different sources must be referenced to
the same datum, ellipsoid, and coordinate format. Different formats
provide different coordinate values for any geographic location. In
North America, the datums NAD-27 and NAD-83 are commonly used
in marine applications.
The DSM 132 receiver outputs position coordinates in several datums
and ellipsoids depending on the source of DGPS being used. See
Table 2.3.
For more information, go to the National Geodetic Survey website:
www.ngs.noaa.gov/faq.shtml#WhatDatum.
Note – To convert GPS positions in the NAD-83 datum to background
maps for the old NAD-27 datum, use the conversion program
Corpscon. This is available free from the Topographic Engineering
Center (http://crunch.tec.army.mil/software/corpscon/corpscon.html).
Table 2.3 DGPS source
Differential Source Datum Ellipsoid
None – Autonomous mode
WGS-84
1
1
World Geodetic System 1984. Datum and ellipsoid.
WGS-84
OmniSTAR 3 North American Beams NAD-83
2
2
North American Datum 1983. Equivalent to WGS-84.
–
OmniSTAR Rest of World Beams ITRF
3
3
International Terrestrial Reference Frame. Contact the DGPS provider for details.
GRS-80
Thales Beams ITRF GRS-80
WAAS Beams WGS-84 WGS-84