You could try summing distances over each pair of successive points in your path (sample it if needed), taking into account the average elevation to calculate the radius in the great circle distance calculation.

See top answer there about taking elevation into account for distance between 2 points http://stackoverflow.com/questions/1108965/taking-altitude-into-account-when-calculating-geodesic-distance

edit: After thinking again, since altitude changes impact on distance may be small compared to the error due to a great circle model, use of proper geodesic model is prefered (https://en.wikipedia.org/wiki/Vincenty%27s_formulae). Another way to see it is to calculate the distance with usual methods (e.g wgs84 and pyproj) for each sub-segment and adjust it using basic geometry: length of hypothenuse of the triangle having the base length calculated

You could try summing distances over each pair of successive points in your path (sample it if needed), taking into account the average elevation to calculate the radius in the great circle distance calculation.

See top answer there about taking elevation into account for distance between 2 points https://stackoverflow.com/questions/1108965/taking-altitude-into-account-when-calculating-geodesic-distance

edit: After thinking again, since altitude changes impact on distance may be small compared to the error due to a great circle model, use of proper geodesic model is prefered (https://en.wikipedia.org/wiki/Vincenty%27s_formulae). Another way to see it is to calculate the distance with usual methods (e.g wgs84 and pyproj) for each sub-segment and adjust it using basic geometry: length of hypothenuse of the triangle having the base length calculated

You could try summing distances over each pair of successive points in your path (sample it if needed), taking into account the average elevation as a radius in the great circle distance calculation.

See top answer there about taking elevation into account for distance between 2 points http://stackoverflow.com/questions/1108965/taking-altitude-into-account-when-calculating-geodesic-distance

You could try summing distances over each pair of successive points in your path (sample it if needed), taking into account the average elevation to calculate the radius in the great circle distance calculation.

See top answer there about taking elevation into account for distance between 2 points http://stackoverflow.com/questions/1108965/taking-altitude-into-account-when-calculating-geodesic-distance

edit: After thinking again, since altitude changes impact on distance may be small compared to the error due to a great circle model, use of proper geodesic model is prefered (https://en.wikipedia.org/wiki/Vincenty%27s_formulae). Another way to see it is to calculate the distance with usual methods (e.g wgs84 and pyproj) for each sub-segment and adjust it using basic geometry: length of hypothenuse of the triangle having the base length calculated