Earl’s Alidade

After two years of planning, construction, and cajoling, Earl Raymond, Maine IAT’s official surveyor and trail router extraordinaire, was joined by a group of Maine IAT board members and friends on Deasey Mountain to install a replica of the original alidade used by wardens to pinpoint the locations of forest fires in Maine’s north woods.

When installing an alidade, alignment is key!

An alidade consists of a circular map, oriented to align with true north, and a center mounted horizontal bar with two vertical sighting vanes.

Close look at the circular map. Note the mountain profiles and compass points around the outer edge.

The bar is rotated while the fire warden sights through the vanes on a distant object (a wisp of smoke, for example). The warden can then note the bearing of the object on the map. When a second warden on a different mountain sights on the same wisp, the two bearings can be be used to triangulate the location of a fire.

How many people can you fit into an 8×8′ cabin? (l to r) Nate Norris, Dan Swallow, Chunzeng Wang, Dave Rand, Kirk St. Peter, Earl Raymond, Nancy Hathaway, Ford Stevenson and Susan Adams.

After installing the device, Earl gave his group of helpers (all of whom managed to squeeze into the small 8 x 8-foot lookout cabin) a quick lesson on alidade use which you can see on this YouTube video.