VBOX IISX – Dual Antenna (VB2SL)

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Vbox 2SX

VBOX IISX – Dual Antenna (VB2SL)

The VBOX IISX is a powerful instrument used for measuring the speed, position and angle of a moving vehicle. It is based on a new generation of high performance satellite receivers, and will measure acceleration figures, braking distances, lap times, cornering forces, slip angle, pitch angle and more.
The VBOX IISX dual antenna has all of the same features as the VBOX IISX single antenna version, but contains a second GPS engine. By utilising two GPS engines configured in a ‘Fixed baseline RTK setup’, extra parameters can be measured which are not normally available from a single point GPS setup.
These parameters include Slip angle and Pitch angle (or in an alternative configuration roll angle).

How Does it Work?

The two antennas are placed on the vehicle a set distance apart. This distance is then entered into the VBOX using the front panel and display. An algorithm then uses this ‘Fixed baseline’ to determine the relative position and height of each antenna to a few millimetres. This can be done because errors received at one antenna can be used to cancel out errors at the other antenna, given the known distance between the two.

slip-antennas1Antenna Setup Made Easy

Knowing the relative position of each antenna gives a very accurate ‘true heading’ of the straight line drawn between them.


slip-antennas2Slip Measurement Made Easy

The normal GPS heading can then be compared against this ‘true heading’ to calculate the slip angle (or sometimes referred to as yaw angle)

Knowing the relative height gives a very accurate angle between them, and this gives the pitch angle if configured longitudinally (down the roof), and roll angle if configured laterally (across the roof). In both orientations, the slip angle can still be measured, the user just has to apply a 90 degree offset which is available through the front panel.

Note: The slip angle varies across the width of the car, so it is important to place the antenna directly above the point at which you wish to measure this angle. Ground plane Antennas can be mounted outside of the body of the vehicle using a suitable mount (see picture on the right)slip-antennas3


How accurate are the results?

The accuracy of the slip angle and pitch angle depend on the separation of the antennas and the quality of the antennas which are used.

The wider the separation of the antennas, the better the accuracy you will achieve:

Separation Slip angle Pitch angle
0.5m 0.5° rms 1.0° rms
1.0m 0.25° rms 0.5° rms
2.0m 0.1° rms 0.25° rms



We supply propriety, magnetic mount, ground plane antennas which have been optimised for use in this application to give the best results. To obtain these accuracies, the distance between the antennas needs to be accurate to within 0.5cm, and the system used in a clear, open area without any trees, tall masts, fences or buildings nearby.

What can I use it for?

The Dual Antenna VBOX IISX can be used for all of the same tests as the normal VBOX IISX, but in addition:
Dynamic Tests – Slip and pitch angles updated at 20Hz alongside speed, distance and acceleration
Steady State Cornering – Slip angle without any drift or correction over time
Trailer Angles – Measure relative angles between two fixed bodies (two systems needed)