# Caliper

Use the Caliper section of the Settings tab to shape all the calipers the Find Line tool uses to locate edges or edge points.

Feature | Description
--- | ---
Number of Calipers | Controls the number of calipers to use along the line segment. The tool requires a minimum of two calipers, although using more allows the tool to generate a better fit. In addition, you should use more than two calipers if you allow the underlying Fit Line tool to ignore one or more points while calculating the best fitting line. To determine which point to ignore, the Fit Line tool considers all possible subsets and keeps the set that produces the best possible score.
Search Length | Controls the amount of image perpendicular to the expected line segment that each caliper takes into consideration. You can use the Find Line graphics to specify a general search length or use this field to enter a precise value.
Projection Length | Controls the amount of image parallel to the expected line segment that each caliper takes into consideration. You can use the Find Line graphics to specify a general projection length or use this field to enter a precise value. You should not specify a projection length that causes the individual Caliper tools to overlap or the tool might produce unexpected results.
Search Direction | Controls the direction in which each caliper searches for edges or edge pairs. By default, the search direction is +90 degrees as measured from the expected line segment. To avoid including extraneous edges or other image features inside a caliper, you can adjust the skew of the calipers by specifying a different value for the search direction. You can use the Find Line graphics to modify the direction or use this field to enter a precise value.
Swap Search Direction | Reverses the search direction by subtracting 180 degrees, or adding 180 degrees if the search direction is already a negative value.