The latitude-longitude coordinates are expressed in decimal degrees but what datum was used?
The current use of Global Positioning Systems and Geographic Information System software has increased awareness of the importance of recording datums and ellipsoids. However, this information was not commonly recorded in the past and it wasn’t recorded for the NURE HSSR program. We do know that during the time these samples were collected (late 1970’s and very early 1980’s), there were very few choices of datums or ellipsoids in use within the United States. Most of the NURE HSSR sample sites were plotted on and then digitized from U.S. Geological Survey topographic maps or locally available county maps. Almost all, if not all, USGS maps available during this time were based on the North American Datum of 1927 (NAD27) that used the Clarke 1866 ellipsoid. Many of the available county maps were projected using the State Plane Coordinate System and also marked with latitude and longitude tick marks. It is probably safe to assume that the NAD27 datum and Clarke 1866 ellipsoid were also us
