Mocomi & Anibrain Digital Technologies
Mocomi: What Is a Compass?
Provides basic information about compass points.
Discovering Lewis & Clark
Discovering Lewis & Clark: Portage Route Survey
Features an example of a route survey conducted by William Clark in 1805 of the falls, rapids, cascades and ravines from the lower portage camp to the upper falls (Black Eagle) and beyond, using a circumferentor (surveyor's compass) to...