GPS, Running Watches, Phones, Accuracy and other stuff

Part 1 - Why?

OK, on various posts on the Lonely Goat Facebook Running Club group people have talked about accuracy of their devices they use to track runs.

Frequently I have seen comments like "You should get a running watch" or "You're using a phone, phones are not good at tracking"

Now, I can't let that go.  Over the last 15 years, part of my day job has been to provide support and advice on GIS. Part of this has involved setting up "in field" data capture using various GPS tech.

My immediate predecessor where I worked had spent a large sum of money on massive GPS units.  These were never used as the were powered by heavy lead/acid batteries and were worn like a backpack.

Since then ,every so often I've delved into the world of GPS an looked at the accuracy.

Phones and wearables, as far as I know all have similar accuracy and depend on a few factors.
  • The number of satellites it can see
  • The availability of A-GPS - basically data that assists the processor in getting a fix
  • Full stuff that can effect here.

A smartphone will connect to one or more satellite networks. There are four major satellite networks: GPS (USA), Glonass (Russia), Galileo (Europe) and Beidou (China). Most smartphones use the GPS network and others can use GPS and also Glonass.

Most phones these days connect to at least two of these constellations, my Sony connects to three and some will do all four.

Realistically, getting anything under 3m accuracy is pretty good.

So, back to the comments about running watches vs phones.  For running watches people really mean Garmin. These seem by far to be the market leader.

Garmin don't seem to promise much more than sub 10m accuracy - "Garmin GPS receivers are typically accurate to within 10 meters"

So with no promises that they are any better than my phone, what is behind the perception that phones are no good?  And how do I quantify this?

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