NorthStar 2201 Installation Manual page 10

SECTION ONE Introduction
Understanding the 2201
and 2201/NMEA
Understanding WAAS
satellite differential
Page 2
The 2201 is available in either of two configurations:
•
2201 (binary output) — for interfacing with new and
existing Northstar 941X/XD, 951X/XD, and 952X/XD units
in order to provide WAAS differential corrections. (In the
future, the 2201 will be able to interface with Northstar's
961X/XD and 962X/XD.)
•
2201/NMEA (NMEA) — for interfacing directly with
autopilots, plotters, components of integrated or
standalone marine navigation systems that accept NMEA
0183 data, or NMEA 0183-compatible laptop PC's, in order
to receive WAAS differential-corrected GPS position data.
NOTE: For the binary 2201 to provide WAAS corrections to
a Northstar 941, 951, or 952, these units must be
running software version 3.18 or higher. To obtain
an Upgrade CD and a PC loader cable (Northstar
part number 1100-LC), dealers should contact the
Northstar Sales Department. End users should
contact their local Northstar dealer for upgrading.
As with Coast Guard radiobeacons, WAAS satellites use
surveyed reference stations to monitor GPS signals from each
visible satellite and determine if errors exist, and then develop
corrections. However, unlike Coast Guard radiobeacons or
other land-based transmitters on other frequencies, WAAS uses
a network of geostationary communication satellite
transponders, in fixed positions at approximately twice the
distance from the earth's surface as the orbiting GPS satellites,
on the same frequency as GPS.
These satellite-based transmissions provide consistent position
corrections over a much greater contiguous geographic
location than the other radiobeacons. WAAS differential
corrections maintain a position accuracy of better than 3
meters 2dRMS, without the signal interference problems
periodically experienced with low-frequency, shore-based
radiobeacon differential signals.
2201 INSTALLATION MANUAL, Revision B