The Measurement Sum tool is used to find the sum of all the Measurements in a selected region. The region can be selected using either a rectangular area or a circular area. The sum will only include Measurements that correspond to the currently selected Reference Length, and the sum itself will simply be a Text Path centered in the selected region. You can move the text anywhere you like after construction using one of the Transformation tools such as the Move tool. There are only two other construction options: Scale and Prefix. Prefix is simply a convenience option to add either “Sum:” or “Total:” to the calculated sum. You can change the text to whatever you want later using the Change Text tool. The Scale option allows you to construct the text at either the current Zoom Scale of the canvas or at some multiple of the scale used to construct the Reference Length segment (this is so so that you can match the text size of the sum to the text size of the Reference Segment). Here’s an example of using the Measurement Sum tool.