Does anyone know how accurate geodesic measurement is compared to planar measurements in UTM WGS84 for distances below 15km? We'd like to inform our users about measurement accuracy when using tools based on geodesic measurements. Some of these measured distances are critical because we have to comply with margins regulated by law.
Some tests (3km line drawn in UTM32 WGS84 and measured geodesic) have shown that the difference can be up to 0,5%. Can anyone confirm this? Maybe based on literature or formula? I couldn't find anything in the Internet...
Or am I completely wrong and both measurements have to be identical within one UTM zone because they are based on the same ellipsoid (WGS84)?