Garmin GPS 48 - Manual (Page 56)

Interface Setup
The GPS 48’s interface page lets you specify the for-
mats for connecting external devices. There are six
options: GRMN/GRMN, None/None, RTCM/None,
RTCM/NMEA, NMEA/NMEA, and None/NMEA. Each
option lists the input format first, followed by the output
format.
To select I/O format:
1. Highlight the I/O field, and press
E
.
2. Select the desired setting, and press
E
.
The GRMN/GRMN setting is a proprietary format
that lets you exchange information such as waypoints,
routes, and track logs between two GARMIN GPS units
or a GARMIN GPS and a PC. There are eight data trans-
fer options: send alm, send wpt, send trk, send rte,
request alm, request wpt, request trk, request rte.
To select a transfer option:
1. Highlight ‘HOST’, and press
E
.
2. Select a desired setting, and press
E
.
To disable all interfacing capabilities, select the
None/None setting. If you want to output NMEA data
without any differential input capability, select
‘None/NMEA. Once a NMEA output setting has been
selected, the NMEA field will become highlighted. NMEA
formats 0180, 0183 or 0183 (1.5 or 2.0) are available.
The data transfer rate can be set to 130, 300, 600, 1200,
2400, 4800 or 9600 baud.
DGPS Interface
The last two format settings allow the differential-
ready GPS 48 to accept RTCM DGPS corrections in
RTCM 104 version 2.0 format. Using DGPS corrections
will improve receiver accuracy to 1-5 meters, regardless
of errors induced by the government’s Selective
Availability (SA) program. Two RTCM options are avail-
able: RTCM/NONE, which allows connection to a beacon
receiver with no output capability; and RTCM/NMEA,
which allows DGPS input and NMEA output.
Once a RTCM setting has been selected, the GPS 48
will either automatically try to tune the last frequency
and bit rate you selected or will switch to the default fre-
quency of 304.0 kHz with a bit rate of 100 bps if no pre-
vious beacon has been tuned. You may also enter your
own frequency and bit rate if desired.
Interface Setup
REFERENCE
52
Choose an interface
option based upon what
equipment you are using
to transfer information.
Once the RTCM option is
selected the GPS 48 will
automatically tune itself
or display a default fre-
quency.
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