Gee, that's a disparity. Who was nearer?
I think the correct answer is somewhat in between, probably around 11 or 12km.
To be fair: I did not turn on the GPS, because I don't really care.
The health app only counts the steps taken, and it does not do this very accurately, and it had no way to measure the correct distance -- I suspect it does an approximation of the distance based on the average human step.
Google Maps may be more accurate, but it's more of a complicated drawing I did on the web site, and not a recording of my walk on the phone.
So: completely fuzzy! Just the way I like it!
Regardless, it was probably good exercise.
"I appreciate SDF but it's a general-purpose server and the name doesn't make it obvious that it's about art." - Eugen Rochko