The tape measure has a readout that displays the distance between its ends in world units. Since a tape measure is a track, it has a menu that is accessible in the Tracks menu on the menu bar or by right-clicking the main video view.

1. Displaying the Tape Measure

Display the tape measure by clicking the Tape Measure button on the toolbar. In the main video view, drag the center of the tape to move it or either end to change its length or orientation.

2. Setting the Fixed Tape Property

By default, the tape measure is fixed--that is, its end positions do not vary from frame to frame. Turn off the Fixed property in its track menu to allow the end positions to vary.

Note that fixing the tape measure is not the same as fixing the scale of the coordinate system!

3. Setting the Scale (Calibrating the Image)

To calibrate a video image, first set the two ends of the tape measure at positions that are a known world distance apart. Then double-click the readout and enter the known distance.

4. Locking the Tape Measure

Locking the tape measure prevents it from making any changes to the scale. Lock the tape by turning on the Locked property in its track menu.