@idefix37 I turned the speed thing on and now it seems to be more accurate. The gpx files list my exact coordinates once per second for the duration of the ride. I don't know why windy is ignoring that data and forcing me to set a constant speed.
Also, scrolling the timeline to the side to change the start date doesn't work well. If I only change it forward or back by one or two hours the graph isn't re-drawn. I have to scroll pretty far, like to the next day, and then back to the time I want to see the graph for.
Maybe the app works better?
(PS: Despite being in Colorado I'm actually on the edge of the great plains. My apartment is a mile from the Nebraska border.)