Data Anti Aliasing; Vehicle Profiles; Odometer Pulse Length; Odometer Automatic Pulse Length Calibration Procedure - Advanced Navigation Spatial Dual Reference Manual

inaccurate and in some cases it can cause the filter to reset.
By default Spatial Dual comes configured in the lowest sensor ranges. In this
configuration it is possible to send the gyroscopes over range by quickly rotating the
unit in your hand. It is recommended to watch what happens in Spatial Dual Manager
when you do this.
The sensor range can be set using the sensors range dialogue in Spatial Dual
Manager, see section 11.8.2.
10.6

Data Anti Aliasing

Internally Spatial Dual's filters update at 1000 Hz. When Spatial Dual outputs data,
most applications require the data at a much lower rate (typically < 100 Hz). This
causes a problem for time based data such as velocities and accelerations where
aliasing will occur at the lower rate. To prevent this problem, if the output rate is lower
than 1000 Hz, Spatial Dual will low pass filter the values of the time dependent data
between packets to prevent aliasing. This is only the case when a packet is set up to
output at a certain rate. If the packet is simply requested no anti aliasing will occur.
Additionally there is no anti aliasing for non time dependent fields such as position.
10.7

Vehicle Profiles

Spatial Dual supports a number of different vehicle profiles. These vehicle profiles
impose constraints upon the filter that can increase performance. If your application
matches one of the available vehicle profiles, it is recommended to select it for use in
the filter options dialogue in Spatial Dual Manager, see section 11.8.3. For a list of the
different vehicle profiles please see section 13.10.6.1. Please note that if the wrong
vehicle profile is selected it can cause a significant decrease in performance.
10.8

Odometer Pulse Length

For Spatial Dual 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 Dual. To enter the pulse length
manually, please use the odometer configuration dialogue in Spatial Dual Manager. To
automatically calibrate the odometer pulse length please use the procedure listed
below in section 10.8.1. By default the odometer will automatically calibrate itself.
10.8.1

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 Dual
Manager, see section 11.8.8.
2. Open Spatial Dual Manager, connect to Spatial Dual and open the odometer
configuration dialogue. In the odometer configuration dialogue tick the
automatic pulse length calibration check box and press the write button, see
section 11.8.8.
3. Wait until Spatial Dual has a continuous GNSS fix and then drive 1000 metres
Spatial Dual Reference Manual
Page 46 of 137
Version 2.3
12/04/2016