32 G12 OEM Board & Sensor Reference Manual
more satellites are used in the position solution and the VDOP value is
below the VDOP mask, whichever is most recent.
• Fixed Altitude Mode 1
Only the last altitude entered through the command $PASHS,ALT is used
in the position fix solution.
On initial power-up, or after issuing the $PASHS,INI command (initialize memory)
or $PASHS,RST command (restore defaults), the antenna altitude is set to zero.
Geoid Model
The G12 uses the Ohio State University 91A geoid model (OSU91A). For more
information on OSU91A, refer to the Ohio State University:
Rapp, R.H., Y.M. Wang and N.K. Pavlis, 1991: The Ohio State 1991
Geopotential and Sea Surface Topography Harmonic Coefficient Models,
Report No. 410. Columbus: Department of Geodetic Science and
Surveying, The Ohio State University.
The Ohio State University
Department of Civil and Environmental Engineering and Geodetic Science
470 Hitchcock Hall
2070 Neil Avenue
Columbus, OH 43210 USA
Tel: 614-292-2771
Fax: 614-292-3780
Web: http://www-ceg.eng.ohio-state.edu
Ionospheric Model
The G12 can use ionospheric and tropospheric models in its position
computations to compensate for errors caused by ionospheric and tropospheric
delay. This mode of operation is typically used to improve autonomous accuracy
by minimizing the influence of the ionosphere and troposphere on the code phase
of the GPS signal. When the G12 is in differential mode (base or rover),
ionospheric and tropospheric modeling is disabled because differential GPS
already compensates for delays associated with the ionosphere and troposphere.
When the receiver is in autonomous mode, ionospheric and tropospheric
modeling is enabled.
DEFAULT SETTINGS
$PASHS,FIX— Fixed Altitude Mode (0)
G12RevD.book Page 32 Tuesday, April 2, 2002 4:33 PM
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