Using the transparent radial distance scale
(Costa Rica political and physical maps)
Press the left mouse button
when the cursor is over the bar at the top of the scale or the arrow icon
and while keeping the button pressed, drag the scale over the map. Release
the mouse button when the center is over the starting point or the destination.
You can now measure the streight line distance between two points. The illsutration
shows that the streight line distance between Quepos and Jaco
is 50 kms.