An orthodromy measure is represented by a line on a map.
This is useful for defining the shortest distance between any two
points selected on the map. The total distance between the two points
is computed and displayed next to the line. Depending on the length
of the line and the zoom scale, the line may not be straight due to
the curvature of the Earth. A Measures layer is added to the Map Layers
pane.
The following figure shows an example of a Measures layer
with a curved orthodromy measure displayed.