The Excalibur Orion Curvimeter, also known as an opisometer, meilograph, or map measurer, is designed for measuring lengths of curved lines on topographical maps such as roads, railways, rivers and other curved line features. Curvimeters are also used for draft plans and drawings.
To use the Curvimeter, set the pointer to zero by turning the small tracking wheel at the base of the measurer. Place the tracking wheel onto the map and roll it over the map following the line of your course such as a river, road or railway. As the tracking wheel rolls over the map, the dial pointer rotates to record the distance. When you stop rolling the tracking wheel over the map, the dial pointer will indicate the total distance covered for the particular scale of your map.