GPS-R35 User Manual
Levave
www.levave.com
Page 5 of 17
1.3.3. Firmware Characteristics
Items Description
Core of firmware SiRF version 2.3
Baud rate 9600
Code type NMEA-0183
Datum WGS-84
Protocol message &Output frequency GGA(1Hz), GSA(1Hz), GSV(1Hz), RMC(1Hz),VTG(1Hz)
1.3.4 Interfaces
1) Dual channel RS-232 or TTL compatible level, with user selectable baud rate
(4800-Default, 9600, 19200, 38400).
2) NMEA 0183 Version 2.4 ASCII output (GGA, GSA, GSV, RMC, option GLL, VTG, ZDA).
3) Real-time Differential Correction input (RTCM SC-104 message types 1,2 and 9).
4) SiRF binary protocol.
2. Operational characteristics
2.1 Initialization
As soon as the initial self-test is complete, the GPS-R35 begins the process of satellite
acquisition and tracking automatically. Under normal circumstances, it takes approximately
42 seconds to achieve a position fix, 38 seconds if ephemeris data is known. After a position
fix has been calculated, information about valid position, velocity and time is transmitted over
the output channel.
The GPS-R35 utilizes initial data, such as last stored position, date, time and satellite
orbital data, to achieve maximum acquisition performance. If significant inaccuracy exists in
the initial data, or the orbital data is obsolete, it may take more time to achieve a navigation
solution. The GPS-R35 Auto-locate feature is capable of automatically determining a
navigation solution without intervention from the host system. However, acquisition
performance can be improved as the host system initializes the GPS-R35 in the following
situation:
1) Moving further than 500 kilometers.
2) Failure of data storage due to the inactive internal memory battery.
2.2 Navigation
After the acquisition process is complete, the GPS-R35 sends valid navigation
information over output channels. These data include:
1) Latitude/longitude/altitude
2) Velocity
3) Date/time
4) Error estimates
5) Satellite and receiver status
The GPS-R35 sets the default of auto-searching for real-time differential corrections in
RTCM SC-104 standard format, with the message types 1, 5, or 9. It accomplishes the
satellite data to generate a differential (DGPS) solution. The host system, at its option, may
also command the GPS-R35 to output a position whenever a differential solution is available.
