Collimating the inner tower at Station Winnie.Collimation involved placing the observing instrument directly over the mark.Triangulation party of Carl I. Aslakson
3/18/2019 2:24:54 PM
Date: 21-Aug-34
Credit: Captain Ray Tryon, C&GS;
Location: Itasca County, Minnesota
Subject: Geodesy
Subject: Triangulation
Subject: Towers
Subject: Bilby Steel