Light Mountain Transit — Lolo Pass, ID
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Dunbar Loop
N 46° 38.078 W 114° 34.661
11T E 685406 N 5167413
Before GPS and other satellite navigation technology developed in the late 20th and early 21st centuries, for hundreds of years before surveyors and explorers would rely on transit to survey lands and oceans.
Waymark Code: WM1127W
Location: Idaho, United States
Date Posted: 08/02/2019
Views: 1
In a corner of the Lolo Pass Visitor Center is a simple machine that many people ignore. Yet devices of this nature have helped countless explorers and surveyors around the world since the early ones were developed in the 1500s.
This particular one is from the 1880s and built by the firm W. & L.E. Gurley of New York City. It was considered light enough to carry on arduous surveying trips throughout the United States including the rugged peaks of Idaho and Montana.
The concept was simple. Using geometry, looking through the telescope and knowing the angle you were looking at you could measure the height of mountains and figure out angles of rivers as they coursed along valleys. Then, in turn, you could transcribe these measurements and make maps so that people had a better understanding of the physical world they were in.
From the sign's text:
The Light Mountain Transit
In the days before FPS, laser, aerial and satellite photography, the Forst Service hired men with strong mathematic abilities and backwoods skills to survey the National Forest boundaries.
Manufactures by W. & L.E. Gurley (ca 1885), transit such as this were issued to the Forest Service. The Government's plan of alternate public and private lands ("checker boarding") in mountainous Lolo Pass area would have kept Forest Service surveyors busy for years.