Garmin GPS 100 - Manual (Page 78)

The GPS 100 will automatically guide you along the offset path as you
desired!
12.3 COURSE TO STEER (CTS)
Course To Steer (see Section 5.1) is a GARMIN exclusive that recommends
an optimal direction to steer that will guide you to the course and proceed
efficiently along your route. CTS will even help you steer around a smoothed
turn when using your GPS 100 in an airplane!
As an example, suppose you activate the route illustrated above. The GPS
100 chooses the closest leg with a desired track of 45 degrees but your
position happens to be 2 nautical miles off course. The unit will automatically
compute the optimal course to steer (which is 15° in this example). Simply
go to the CDI page, select "CTS" on line 2, and "TRK" on line 3. Turn your
craft such that your track (TRK) matches the recommended course to steer.
12-3