Garmin GPS 120XL - Manual (Page 48)

To disable all interfacing capabilities, select the
None/None setting. If you want to output NMEA data
to compatible external devices without any differential
input capability, select the None/NMEA setting. Once a
NMEA output setting has been selected (with or with-
out RTCM input), the NMEA field will become high-
lighted. NMEA formats 0180, 0182 or 0183 (1.5 or 2.0)
are available.
To select a NMEA format:
1. Press F to begin a NMEA selection.
2. Use
U
and
D
to select a format, and press
F
.
DGPS Interface
The last two format settings allow the differential-
ready GPS 120XL to accept RTCM DGPS corrections in
RTCM 104 version 2.0 format. Using DGPS corrections
will improve receiver accuracy to 5-10 meters, regard-
less of errors induced by the U.S. government’s Selective
Availability (SA) program. The RTCM/NONE format
will allow connection to any manually tuned beacon
receiver by using the proper output interface. The baud
rate is selectable from the GPS 120XL.
The RTCM/NMEA selection controls the GARMIN
GBR-21 differential beacon receiver. Once a RTCM set-
ting has been selected, the GPS 120XL will either auto-
matically try to tune the last frequency and bit rate you
selected or will switch to the default frequency of 304.0
kHz with a bit rate of 100 bps if no previous beacon
has been tuned. You may also enter your own frequency
and bit rate if desired.
DGPS Interface
REFERENCE
44
The ‘NONE/NMEA?’ set-
ting makes it possible to
output data to output infor-
mation to devices like chart-
plotters and autopilots.
The selectable baud rate is
available for all RTCM
interface options.
120XL Man RevB 7/10/98 10:55 AM Page 44