Tilt Compensation for the SPS986 Receiver and Siteworks

In April 2019, Trimble introduced Tilt Compensation for the SPS986 receiver and Siteworks Controller software. Tilt Compensation is one of the biggest advancements in GNSS Site positioning. It improves accuracy and productivity in the construction workplace.

The productivity gains are in the measuring features and staking mode. In staking mode, the user does not need to re-adjust the point when leveling the rod. When measuring features, the user is not required to level the rod over the feature to get an accurate location, eliminating non-accessibility due to the GNSS antenna. Also, measuring slopes is much safer now as the user does not need to climb mid-slope to get an accurate location.

Without Tilt Compensation, rod leveling is done by a 40 second mechanically adjusted rod-bubble mounted on the rod. Forty seconds means that if the bubble moves 0.006561’, the receiver moves 0.07’ on a 6.56 (2 meter) rod. Typically, after use, the rod is put back in the work truck, where it tends to vibrate out of adjustment.

Tilt Compensation uses an Inertial Measurement Unit (IMU) to project where the rod tip is in space regardless to level and tilt. The internal IMU accuracy is 0.026’ plus 0.001’ per degree, so at 5° out of level the rod tip will be within 0.031’.

As seen in the picture above, the rod is about 5° out of level staking a point measured as control. With tilt compensation on, the rod tip is within 0.01’ by 0.01’. With compensation off, the tip is 0.52’ by 0.15’.