Measurement Tool Error?

Discussion created by drscknowles on Dec 12, 2012
Latest reply on Dec 12, 2012 by MKennedy-esristaff
When I load a basemap (e.g. BingMapsAerial), and perform distance measurements, I find that the returned values are almost 50% too high.  (to determine this, I zoomed in on an American football field and measured the distance between goal posts (120 yards, 360 feet), and get ~476 feet as the return value.  I found this same error on other basemaps that appear when clicking "add basemap", and using different reference distance techniques.  Does anyone know what the source of this error is?  Since it appears to be a constant error, I just multiply any measurement I make by 0.755, but that's a little disconcerting.