Hi Mark,
This sounds a lot like it has to do with the coordinate systems. Can you specify the following:
- coordinate system of your streams dataset
- coordinate system of your data frame
If both are geographic, can you provide me a projected coordinate that suits your data (for the length calculation)? Probably the straight line geometry has to be created with the spatial reference of the source, and if that is geographic, it needs to be projected to obtain the proper length. This can all be done in the field calculator script.
Just to be sure can you also provide an example:
- start coordinate
- end coordinate
- distance measured manually (the correct distance)
- distance calculated by the script
Kind regards,
Xander