Figure 2. First and second order triangulation observations analysed from the Adirondack Survey and U. S. Coast Survey data collected between the 1870s and 1900. Lines observed in both directions are shown as solid, those observed in only one direction have dashed lines towards the target station. The Adirondack Survey data analysed are only a small subset of the data actually collected (see text). The dots are triangulation stations in the NGS database. Superimposed are the locations of the 1992 and 1995 GPS observations.