So I've started getting serious with my 5k training. My current goal is sub 23 minutes, and right now I'm in the 25's. However now that I'm micromanaging the runs more, I'm noticing big discrepancies in the GPS. I have a perfect 5k loop down, yet today for example I reached the end and was a whole third of a mile short!

I'm using my Apple Watch (latest Series 6 with cellular) and the standard Apple Workout app. I searched some setting options online and have all the recommended options on. Is this normal for you Apple Watch users or is something wrong?

I've noted that on my MotoGPower phone. It's a 2021 model, and I'm off 1/8 mile high  every 2 miles

What is its update/sample rate?

Does it measure distance using GPS or some accelerometer/stride rate/stride length calculation?

Garmin isn't any better.

I have had the Tactix Bravo and now Charlie. I jogwalk the same fucking loop. Maybe a foot or two off if I hug the curves instead of staying in the middle. It varies from 1.02 to .90 mile every.single.time.

This is even with using both GPS/GLONASS, 1 second updating, all the other stuff that kills the battery but improves GPS recording.

It's a ball pain, and I was starting to consider something else (for some other reasons), but kind of looks like it's brand agnostic.

One thing I am learning about, and may work for you, is if you're doing the same 'path' (for lack of common terminology), perhaps there is a way to pre-'program' the 'path'. Then, you tell the watch you're doing that 'path' (I think Garmin-speak is 'course'). (shrugs)

You'd think with all the skinny, exercising nerds, this would all be cutting edge, but no. It's as shitty as public safety and mil applications.

Some systems use 'pure' GPS, taking positioning from the constellation.

Many systems attempt to reduce the circular error probability by looking at cell towers and wifi signals. That actually does help in this use case, but, making sure the phone can receive well can be a ball pain when you are wearing shorts and a shirt with no pockets lol

The trail I use has about 60% canopy. Watch and phone don't have much to work with, and my paths show it lol