ashtech DG14, Reference Manual

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42 DG14 and DG16 Board & Sensor Reference Manual
The DG16 can use ionospheric and tropospheric models in its position
computations to compensate for errors caused by ionospheric and tropospheric
delay when needed. 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 DG16 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.
The ionospheric model used by the DG16 is based on the model defined in ICD-
GPS-200, Revision B. The tropospheric model is based on the Bean and Dutton
model. For more information on ICD-GPS-200, refer to ARINC Research
Corporation:
ARINC Research Corporation
2250 E. Imperial Highway, Suite 450
El Segundo, CA 90245-3509 USA
Tel: 310-524-1557
Web: http://www.arinc.com/products_services/gpshome.html
The DG16 uses the Joint US/UK 1995 Epoch World Magnetic Model (WMM-95).
For more information on WMM-95, refer to the USGS National Geomagnetic
Information Center:
USGS National Geomagnetic Information Center
Box 25046, Mailstop 968
Denver Federal Center
Denver, CO 80225-0046 USA
Tel: 303-273-8475
Fax: 303-273-8450
Web: http://geomag.usgs.gov