Spatial Reference Manual
Page 95 of 158
Version 4.4
04/06/2019
12.4.3
Odometer Input
This function is designed for low resolution vehicle speed sensors and odometers. It
expects a normally low input with a high state for the trigger. If the pulse length is
more than 0.1 metres this odometer input function should be used, if it is less than 0.1
metres the wheel speed sensor function should be used. Please contact Advanced
Navigation support for help integrating with your speed sensor.
Parameter
Value
Trigger
Low → High
Maximum Frequency
600Khz
Maximum Pulse Rate
4294967 pulses/metre
Table 21: Odometer input specifications
12.4.4
Zero Velocity Input
In this function, a high state indicates to Spatial that the vehicle is stationary. The low
state indicates that the vehicle could be moving. Use of this function can significantly
improve drift performance when a GNSS signal is not available.
12.4.5
Pitot Tube Input
This function is designed for fixed wing aircraft to enhance navigation through the use
of a pitot tube to measure airspeed. It requires a differential pressure sensor that has a
frequency output such as the Kavlico P992 (frequency output option) or the
Paroscientific series 5300. Please contact Advanced Navigation support for help
integrating with a pitot tube.
12.4.6
NMEA Input
This function accepts external data in the NMEA format. Advanced Navigation
recommends against using NMEA where possible due to the inefficiency, inaccuracy
and poor error checking of the format. All NMEA messages received must have a valid
checksum. Supported messages are listed below. The recommended combination of
messages are GPGGA, GPVTG and GPZDA with optional messages GPGSV and GPGSA.
