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A Manual of Topographic Methods by Henry Gannett, USGS Chief Topographer published in 1893 #TBT https://t.co/7JvIgRoXuH https://t.co/rthFqjLdT4
A Manual of Topographic Methods by Henry Gannett, USGS Chief Topographer published in 1893 #TBT https://t.co/7JvIgRoXuH https://t.co/rthFqjLdT4