When comparing my Bad Elf GPS track to my AMOD track, I wanted some mathematical calculation of the difference. I don’t really know even what that’d mean, but matt_c pointed me to some ideas:

- Hausdorff Distance (PostGIS, GEOS, explanation). My quick read suggests this will calculate the maximum divergence between the two tracks, not the sum of many little errors.
- Fréchet distance. “The Frechet distance is a measure that takes the continuity of shapes into account and, hence, is better suitedthan the Hausdorff distance for curve or surface matching” (source).

This sounds complicated.