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GPS 18 Technical Specifications (190-00307-00) Rev. D
Page 15
4.2 TRANSMITTED NMEA 0183 SENTENCES
The subsequent paragraphs define the sentences that can be transmitted by the GPS 18 PC and LVC.
4.2.1 Sentence Transmission Rate
Sentences are transmitted with respect to the user selected baud rate.
The GPS sensor will transmit each sentence (except where noted in particular transmitted sentence
descriptions) at a periodic rate based on the user selected baud rate and user selected output sentences. The
GPS sensor will transmit the selected sentences contiguously. The length of the transmission can be
determined by the following equation and Tables 2 and 3:
total characters to be transmitted
length of transmission = ---------------------------------------------
characters transmitted per second
Sentence Output by Default? Maximum Characters
GPRMC
74
GPGGA
82
GPGSA
66
GPGSV (PC and LVC only) 70
PGRME (PC and LVC only) 35
GPGLL 44
GPVTG (18-5Hz only) 42
PGRMV 32
PGRMF 82
PGRMB (PC and LVC only) 40
PGRMT Once per minute 50
Table 2: NMEA 0183 Output Sentence Order and Size
Baud Characters per Second
300 30
600 60
1200 120
2400 240
4800 480
9600 960
19200 1920
38400 3840
Table 3: Characters per Second for Available Baud Rates
The maximum number of fields allowed in a single sentence is 82 characters including delimiters. Values
in the table include the sentence start delimiter character “$” and the termination delimiter <CR><LF>. For
the GPS 18 PC and LVC, the factory set defaults result in a once per second transmission at the NMEA
0183 specification transmission rate of 4800 baud. For the GPS 18-5Hz, the factory set defaults will result
in a five times per second transmission at 19200 baud.
For the GPS 18 LVC: Regardless of the selected baud rate, the information transmitted by the GPS sensor
is referenced to the one-pulse-per-second output pulse immediately preceding the GPRMC sentence, or
whichever sentence is output first in the burst (see Table 2 above).
For the GPS 18-5Hz: Regardless of the selected baud rate, the information transmitted by the GPS sensor is
referenced to the preceding five times per second output pulse.