I have an Excel-file with coordinates (WGS84). From these coordinates I create a line (shp) and transform it (ETRS89). After the transformation I calculate the distance from point to point. I do this using a Python-script and ArcGIS.
However, I would like to calculate the distance between the points before I run my script and without an ArcGIS license. I found several answers to that question (i.e. John Cook,Heversine I,Heversine II and Heversine III). But they are all not accurate enough. I would like to get exact the same value as I get using "Calculate Geometry" in ArcGIS in ETRS89) without using ArcGIS. There is only a difference of a few centimeters, but in sum it is a few kilometers. Is there any option to do that? Any special libaries, which allow to transform coordinates and calculate the distance?