Working on using a Kalman filter to improve my distance calculations during GPS tracked workouts. Two observations:

A) I've never felt more like the “I have no idea what I'm doing" dog meme. Math can be very difficult.

B) Having spent all day looking at GPS traces from various devices, it is striking just how good the dual band receiver in an Apple Watch Ultra is compared to older iPhones. My processing has almost affect on most Ultra traces, but can massively improve iPhone traces.