Overview
The CAN Wheel Speed Input feature allows OXTS products to use wheel speed data from a CAN bus to improve navigation accuracy, particularly when GNSS signals are weak or unavailable.
This guide explains how to:
Configure your OXTS unit to receive CAN wheel speed data
Optimize the setup using the correct parameters
Verify that the wheel speed input is working correctly
Requirements
Before starting, ensure the following are available:
Device has CAN Acquisition and GAD feature codes enabled
NAVsuite 3.13 or later installed on your PC
Firmware version 240917 or later installed on your device
A vehicle CAN Bus transmitting wheel speed data
The correct DBC file for your CAN Bus
Configuration
You can configure CAN wheel speed under the Interfaces → CAN Acquisition and Advanced → CAN Wheel Speed tabs
Step 1 — Configure CAN Acquisition
Go to the Interfaces → CAN Acquisition tab.
Tick Enable CAN Interface.
Load the DBC file that defines your CAN messages.
-
Tick Enabled on the message that provides wheel speed data.
The signal information should automatically populate from the DBC file.
Note: this will only enable the signal to be acquired - further configuration required to enable use as wheel speed input
Step 2 — Configure CAN Wheel Speed
Navigate to the Advanced → CAN Wheel Speed tab.
Enable the speed signal identified in step 1.
-
Set the parameters of the signal.
Refer to the Optimising Configuration Parameters section below
Navigate to the Lever Arm sub-tab and enter the linear offsets from the IMU to the wheel speed sensor
Your OXTS unit is now configured to receive and interpret wheel speed data from the CAN interface.
Optimising Configuration Parameters
Accurate wheel speed data depends on correctly tuning several parameters. These can be set and refined using recorded datasets compared against the OXTS NCOM speed outputs under good GNSS conditions.
| Parameter | Purpose | How to Tune |
| Unit Scale (m/s) | Converts the raw CAN signal into m/s. | Typically read directly from the DBC file. Confirm the value results in speeds displayed in m/s. |
| Latency (s) | Accounts for delay between wheel speed measurement and arrival at the OXTS device. | Plot CAN and NCOM speeds. Adjust until peaks and transitions align. |
| Real-World Scale Factor | Corrects for consistent over- or under-reporting of CAN speeds. | Compare average CAN and NCOM speeds. If CAN speeds are 5% too low, set the scale factor to 1.05. |
| Scaling Error | Percentage uncertainty of the CAN signal. | Use the standard deviation of (NCOM speed ÷ CAN speed) ratios after tuning scale and latency. |
| Measured Absolute Error (m/s) | Represents noise or minimum measurable error. | When the vehicle is stationary, take the average non-zero CAN speed or use half the smallest measurable non-zero speed. |
Tips:
Start with simple values (e.g., scale factor = 1.0, latency = 0).
Refine using recorded data and visual comparisons in NAVgraph.
Please contact support@oxts.com for assistance with parameter optimisation.
Verifying CAN Wheel Speed Usage
To confirm that your OXTS device is actively using the CAN wheel speed input:
Open the NCOM stream of device in NAVdisplay.
Open a new graph widget for Wheel Speed Innovations measurement.
If the innovations are updating and small in magnitude, the system is successfully integrating CAN wheel speed data into its navigation solution.
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