What does NAD27 and NAD83 mean?
NAD refers to the North American Datum and is a set of parameters that helps define a spherical coordinate system. There are two main datums used in the USNAD27 and NAD83. The center point for NAD27 is Meades Ranch in Kansas and used the Clarke spheroid of 1866. The center point for NAD83 is the center of the earth’s mass and uses the GRS80 spheroid which factors in the earth’s equatorial bulge.
