Magellan GPS PROMARK X User Manual page 136

Appendix ProMARK X
RTCM Corrections.
RTCM corrections are determined by a GPS receiver at a control site, which
are broadcast by a radio beacon at the same site. The difference is that the
GPS receiver at the control site tracks and computes a range error for all
visible satellites. This means that the broadcast corrections are not limited
by distance from the control site or tropospheric conditions.
The ProMARK X can receive RTCM corrections in two ways. It can be
connected to a differential radio beacon receiver (also referred to as a DGPS
receiver or an MSK, or minimum shift key, receiver) such as the Magellan
DBR™ to receive the corrections directly from the beacon. This requires that
the receiver be within range of a beacon (usually 300 miles) and that the
receiver be compatible with the ProMARK X. To be compatible, the
differential radio beacon receiver must receive and demodulate the correc-
tions, then relay them to the ProMARK X through an RS-232 line. The
ProMARK X will then apply the corrections to the positioning information it
collects to calculate and display differentially corrected position fixes.
Alternatively, the ProMARK X can accept RTCM corrections via PC or
telephone modem through its RS-232 data port. This method has no
distance limitations, but does require the appropriate equipment.
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