Hello! I am attempting to make elevation profiles from Polylines and can't get the Profile Graph to chart to be useful. Both using "Create Chart" and the Profile Tool give the same result, a distance x-axis that is miles longer than the distance of the Polyline. I know it's charting it in the Geodesic distance because if I calculate the geometry in a field in the attribute table property Length (geodesic), it charts displays axis values out to that distance value, while I am looking for the Length (3D) for the distances to display on the profile map. When I run the Exploratory 3D analysis Elevation Profile from a Layer, it gives me the correct x-axis length automatically, but I can't use that tool to create the custom profiles because it is so limited in customization (only one unit for both x/y axis). Everything is in WGS1984. This is pretty inconvenient and I can't find what I'm missing anywhere. Any help is appreciated.
Unless you are covering such a large part of the earth so that using geodesic distance is absolutely necessary, I suggest projecting your data into an equidistant projection and working in projected space.
The question and answer both helped me realise that the Elevation Profile tool was calculating distance using the Map's coordinate reference system (CRS).
I had incorrectly assumed it was using the CRS of the elevation surface DEM.
To fix the problem I set the map to a projected CRS. Note, because there is also a Z-plane when doing this sort of work, you first must set the map's Z CRS to none, set the XY CRS to a suitable projected one for the area, then set the equivalent Z CRS.