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SECTION SIX: Interfacing the 957 system
957 INSTALLATION MANUAL, Revision C1 Page 45
• XX.XX ’ (lat/lon precision to two decimal places/
hundredths of minutes/or 60 feet)
• XX.XXX ’ (lat/lon precision to three decimal places/
thousandths of minutes/or 6 feet; this is the factory
setting)
• XX.XXXX ’ (lat/lon precision to four decimal places/
ten-thousands of minutes/or roughly ½ foot)
The 957 conforms to the NMEA version 2.00 standard, and is
also compatible with version 1.50. Electronic and pen plotting
devices typically benefit the most from three and four decimal
places of precision. However, many older devices (and some
current autopilots) designed to operate with the original 0183
and other formats can only function with two-place precision.
Choosing the output rate The default rate for standard NMEA 0183 output is two
seconds. The 957 lets you use a one-second update interval, a
rate of 1 Hz, under limited circumstances, for NMEA and
diagnostic data output. Using the 1-Hz output option requires
some thought when specifying either NMEA 0183 (NMEA
version 2.0) or Raytheon (RAY 0183). Because there isn’t
enough time to transmit all available sentences within one
second, you must select for output only those that are needed.
If you select more sentences than can be output in one second,
the 957 displays the following error message:
SORRY, CAN’T DO THAT. TOO MANY SENTENCES FOR 1 SEC
INTERVAL
In this case, you must select fewer sentences.
There are some applications that need a longer update period.
In that case, you can increase the span to 999 seconds.
Choosing the waypoint
identification (ID)
Many marine devices can display waypoint names if they’re
output by the 957. At the PORT 1 SETUP or PORT 2 SETUP
screen, highlight the NMEA 0183 WAYPT ID AS option, then
press the EDIT menu key. Change the option from NUMBER to
NAME, and press the ENTER key when done. If capable, the
listening device will now display six-character waypoint names.
NOTE:
Position information can be output and displayed to
four decimal places, but the ability to actually
navigate with such accuracy is limited by the
accuracy of the Loran and GPS systems.
Therefore, choosing more decimal places doesn’t
necessarily increase navigating accuracy.