Nmea_Monitor - SeaSpace TeraScan 1.5M Operation And Maintenance Manual

10.3.6 nmea_monitor

Monitors the NMEA data messages sent by external equipment and stores the messages in shared
memory.
Format:
nmea_monitor unit delay
Description:
nmea_monitor reads either (a) the NMEA 0183 messages (V2.10, V2.30, or V3.00), or (b) the NAV1
messages, decodes them, and stores them in shared memory. Programs such as antenna and whereami
will use the data to provide a ship heading, land location if the system is so configured.
NMEA 0183 messages contain current position information (such as latitude, longitude, altitude,
heading, roll, pitch, and speed over ground, or time), and information about the next waypoint of a
route (waypoint number, latitude, longitude, distance, bearing). Not all NMEA devices transmit all
types of data.
NAV1 100-ms messages contain heading, latitude, longitude, and time.
The superuser runs this program that is started by tsched. All other users access shared memory to use
the data.
One or two serial ports can be configured for reading NMEA messages. The ports are numbered 1
and 2. Port [nav-1] always defines the port that supplies ship heading.
If the time is supplied by NMEA messages, unit specifies the port (1 or 2), and delay specifies the delay
between time readings, in minutes.
In order to run nmea_monitor using port [nav-1], the following settings must be defined in the
$PASSDIR/system.config or $PASSDIR/config/system.config file:
[nav-1] nav.type
[nav-1] nav.device
[nav-1] nav.msgfmt
[nav-1] nav.sentences
[nav-1] nav.timeout
type of device associated with the first port (NMEA).
device name of the serial port attached to the first nmea port.
For example: "/dev/term/1".
Message format for data sent to nmea_monitor
0183 v2.10=NMEA 0183 Version 2.10
0183 v2.30=NMEA 0183 Version 2.30
0183 v3.00=NMEA 0183 Version 3.00
nav1-cdg=NAV1 -CDG
(optional setting) Valid NMEA sentences to be read and processed
by nmea_monitor.
(optional setting) Number of seconds to wait for ship heading data before
showing the ship heading as BAD. If the timeout value is =0 or the setting is
not included, then no timeout occurs and the last good heading remains for
TeraScan 1.5m Polar Satellite Tracking Antenna O & M Manual 187