White Paper - SX12 Tracking and Target Separation March 2021 Rev A 2
All Trimble total station use Autolock® technology to find, track, and lock onto prisms. The Trimble SX12 scanning
total station uses a digital camera-based system for its Autolock implementation. One major advantage of the
SX12's camera-based system is that it can better differentiate between multiple reflections within the tracker
field of view.
This means when aiming to permanent target installations, the SX12 requires a smaller prism separation than
what's possible with analogue trackers. Similarly, when tracking, the SX12 is able to keep following the currently
locked target, even when one or more undesired reflective objects come into view of the tracker.
Trimble SX12 Tracker Implementation
The SX12 illuminates the target laser light from its tracker transmitter and aims the instrument toward the
reflected light from the target.
Figure 1. Shows the SX12 illuminating the target from the tracker transmitter and the target reflecting light back
to the instrument.
Light from
tracker
transmitter
Light reflected by
the target
Some key takeaways from this paper include:
• The tracker, EDM and telecamera are all coaxial
• Minimum prism separation depends on prism size and range. The images
of two targets need to be separate on the detector for the tracker to
interpret them as two targets.
• The SX12 has good target separation capabilities: about 40 mm center-
to-center at close distances, and 85 mm at 100 m.
