The Trimble S3 was introduced as an affordable entry level servo instrument. Calling it a servo instrument isn’t quite accurate though because the drive system is magnetic, same as the Trimble S6. The key differences are that the S3 does not have an LED display that is used when initially setting up the instrument and leveling it and it does not offer as many target tracking options as the S6. The S3 only uses a passive tracking technology that works fine as long as the user is working in conditions that do not have a lot of reflective surfaces. The S6 offers tracking targets that will eliminate false targets.

The S3 is approximately $10,000 less than the S6.