So I have two map documents with two different Coordinate Systems set for the layers but using copies of the same shapefile.
Map 1: Coordinate System: NAD_1983_StatePlane_Massachusetts_Mainland_FIPS_2001_Feet Linear Unit: Foot_US The shapefile in this map has same coordinate system but is in Meters.
Map 2: Coordinate System: WGS_1984_Web_Mercator_Auxiliary_Sphere Linear Unit: Meters The shapefile's coordinate system in this map document is in the NAD_1983_StatePlane_Massachusetts_Mainland_FIPS_2001_Feet and its linear unit is Foot_US.
GIS Software is ArcGIS 10.2.2
I am measuring a distance of a building with the measure tool. In map 1 it is telling me the wall is 100 ft long. In Map 2 it is telling me that it is 135 ft long.
Which one (if either) is correct and, how do I know?