Where active safety systems require moving balloon cars, measuring the position of the balloon car can be a problem. In many cases it is only necessary to have the longitudinal position of the balloon car accurate. For these tests the balloon can be towed behind a real vehicle. For safety the length of the towing rope can be as long as 100m.
The latest RT-Range software allows the user to specify the bulls-eye position on the target to be 100m or more. The Target vehicle would be the real car but the measurement position will be 100m behind the real car, where the balloon is towed.
The longitudinal offset feature can be used for fine tuning the balloon’s position. Accurate measurements using a tape measure are not needed since the longitudinal offset feature quickly adjusts any residual error. Just drive the Hunter up to the back of the balloon so that they touch, then set this Longitudinal Range to zero. With this feature the RT-Range gives accurate results and the configuration is simple.
Clearly, when the bulls-eye position is 100m behind the real car, the lateral range will not be particularly accurate. Any small angle change in the real car will have a huge effect on a lateral range that is projected 100m away. The longitudinal range is dependent on the cosine function though and, for small angles, the error will be small.
Image courtesy of Thatcham.