Spatial Reference Manual
Page 57 of 158
Version 4.4
04/06/2019
10.9 Odometer Pulse Length
For Spatial to use a wheel speed sensor or odometer input, it must know the pulse
length of the signal. The pulse length is the distance in metres between low to high
transitions of the signal. The odometer pulse length can either be entered manually or
automatically calibrated by Spatial. To enter the pulse length manually, please use the
odometer configuration dialogue in Spatial Manager, see section 11.8.8. To
automatically calibrate the odometer pulse length please use the procedure listed
below in section 10.9.1. By default the odometer will automatically calibrate itself.
10.9.1
Odometer Automatic Pulse Length Calibration Procedure
1. Ensure that the signal is connected correctly and that the GPIO pin is configured
as an odometer input using the GPIO configuration dialogue in Spatial Manager,
see section 11.8.7.
2. Open Spatial Manager, connect to Spatial and open the odometer configuration
dialogue, see section 11.8.8. In the odometer configuration dialogue tick the
automatic pulse length calibration check box and press the save button.
3. Wait until Spatial has a continuous GNSS fix and then drive 1000 metres over
flat terrain with as little turning as possible.
4. If Spatial loses a GNSS fix for more than several seconds during the calibration,
the distance travelled will be reset. The distance travelled can be checked in the
odometer configuration dialogue to ensure that it has passed 1000m.
5. Once 1000 metres has been driven, check that the automatic pulse length
check box becomes un-ticked and the pulse length value has changed. This
indicates a successfully completed calibration.
10.10 Reversing Detection
Reversing detection is an algorithm that can detect when the vehicle is travelling in
reverse. Knowledge of reverse motion is important when using velocity heading or
odometer input to provide correct results. If Spatial is fitted to a vehicle that does not
reverse or doesn't use velocity heading or odometer, this function should be disabled.
For all other applications it is best to leave it enabled. Reversing detection is enabled
by default and it can be disabled using the filter configuration window in Spatial
Manager, see section 11.8.3.
10.11 Motion Analysis
Motion analysis is an artificial intelligence algorithm that associates patterns in high
frequency inertial data with the speed of the vehicle. After power on it takes some
time to match patterns with speed before it will become active. Motion analysis only
activates when dead reckoning and is most effective when the vehicle is moving
slowly or stationary. Motion analysis does not work in all situations and its primary
benefit is in ground vehicles. It should be enabled in any car application. When active
it can be recognised by 2Hz steps in velocity data. Motion analysis is disabled by
default and can be enabled using the filter configuration window in Spatial Manager,
