Hi Micah, Thanks for the reply. More specifically, I'm working in EPSG:3413 over Greenland. When I convert two map coordinates 1000 m apart to lon,lat, and then pass those to the geod program, it tells me they are closer to 1030 m apart, or that I have a 3% error in distance, and a larger % error in area. Thank you for the hint to use geod. -k.