Using VBOX 4 Products with Wheel Speeds

Introduction

GPS measurement of speed, position and acceleration has become an essential part of the process in assessing the performance of many aspects of a vehicle. Test tracks are rarely perfect places for satellite reception, with trees, bridges and tunnels all having an effect on the quality of the measured data. When the tests are carried out on the road, this problem becomes even greater, with more objects obscuring the direct view to the satellites.

VBOX 4 units can limit these obstacles by utilising the latest multi-frequency, multi-constellation GNSS receiver and integrating inertial and vehicle speed data.
 

Accuracy within a built-up urban area
 

An added advantage of using multi-frequency techniques is the time taken to recover accuracy after a bridge or tunnel is often less than 2 seconds. In areas where there is no view of the sky at all, such as tunnels, inertial sensors and wheel-speeds can fill in the gaps for periods of up to 5 minutes.
 

Accuracy through tunnel

In the data above, you can clearly see the difference that the inertial and wheel-speed data is making to the accuracy of the estimated trajectory, with the IMU doing a good job of estimating the position during the tunnel, ending up with a 15 m error at the end (purple trace). Adding the wheel-speeds into the system (blue trace) significantly reduces the errors, tracking the vehicle through the tunnel with great accuracy.

Configuration

To use wheel speeds, you must first configure the VBOX 4. The configuration steps depend on the hardware and firmware you are using. 

Elevation mask

You may also have to adjust the Satellite Elevation Mask depending on the environment. You can find more information about this here.