My question is about why Google Earth and ArcGIS have such dramatic differences when measuring a line-string. I have an approximately 30 mile trail in Butte County, Northern California. I measured it in ArcMap using 3D analyst, Add Surface Information and draping it over a DEM and it comes to approximately 28 miles. This is UTM 10N. When I export the line as a KML and bring it into Google Earth and look at the elevation profile, it tells me that the length is 33.3 miles, which is wildly different than expected. Does anybody have any thoughts as to why this is so?