190-00266-01
GPS 15H & 15L Technical Specifications
Rev. D
Page 20
4.3
BAUD RATE SELECTION
Baud rate selection can be performed by sending the appropriate configuration sentence to the GPS sensor
as described in the $PGRMC section
, field <10>.
4.4
ONE-PULSE-PER-SECOND (PPS) OUTPUT
The highly accurate one-pulse-per-second (PPS) output is provided for applications requiring precise
timing measurements. The signal is generated after the initial position fix has been calculated and continues
until power down. The rising edge of the signal is synchronized to the start of each GPS second.
Regardless of the selected baud rate, the information transmitted by the GPS 15H & 15L is referenced to
the pulse immediately preceding the NMEA 0183 RMC sentence.
The accuracy of the one-pulse-per-second output is maintained only while the GPS 15H & 15L can
compute a valid position fix. To obtain the most accurate results, the one-pulse-per-second output should be
calibrated against a local time reference to compensate for cable and internal receiver delays and the local
time bias.
The default pulse width is 100 ms, however; it may be programmed in 20 ms increments between 20 ms
and 980 ms as described in $PGRMC section
, field <13>.
4.5
RECEIVED RTCM DATA
Position accuracy of less than 5 meters can be achieved with the GPS 15H & 15L by using Differential
GPS (DGPS) real-time pseudo-range correction data in RTCM SC-104 format, with message types 1, 2, 3,
7, and 9. These corrections can be received by the GPS 15H & 15L on COM 2. The RTCM data must be
received at the same baud rate as the COM 1 port. For details on the SC-104 format, refer to RTCM Paper
134-89/SC 104-68 by the Radio Technical Commission for Maritime Services.
