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GPS track off by several miles

6113274
over 5 years ago
On a couple of recent bike rides my 945’s GPS track has been off from my actual course by four or five miles for a period of 20 to 30 minutes. see the following activity for an example: 
The recording shows that I started my ride over the ocean, about 5 miles west of my actual starting point. The recording shows me traveling east then south, when I actually travelled north then east. During my ride I realized that something was wrong when I saw that my speed was reported as 31mph instead of maybe 15mph. I stopped the activity above and started a new one, and the new activity picked up my actual position and followed my actual path.
Is anyone else experiencing this? It’s very frustrating to start an activity without knowing whether or not my watch has locked onto my actual location. I waited until the watch showed that it had acquired GPS before I started the activity above. I don’t understand why the watch did not identify my correct position over the course of twenty minutes, especially when it immediately picked up my correct position once I started a new activity.
I’ve experienced this issue two or three times in the last two weeks, since loading the 2.8.0 firmware.
  • 0 over 5 years ago

    I have experienced something similar - an out and back run along the same footpath had the tracks off by a long way - see image. I pressed start about 1 minute afer the satellite indicator locked and went green - the start location is way off, and took about 3.5km to find my actual position. I did a GPS soak for over 30 minutes after 2.80 installed and did a hard reset. I use 1 second recording and GPS + GLONASS. Also there is barely any tree cover on this run and no tall buildings as I started the run on the bridge away from the city. Pretty frustrating. 

  • 0 over 5 years ago in reply to cull_27

    That's very common problem around water surfaces. Water surfaces are acting almost like a mirror, so there are a lot reflected GPS signals and they are responsible for so called GPS multipath errors. Also, this is not problem that happens always, because it heavily depends on other atmospheric condition above water surface.

  • 0 over 5 years ago in reply to bane.lukic

    Thanks - an interesting point. I have never seen this before and I have run this route many times over the years. I am hoping it is a fluke and not the watch - I have not had my 945 for very long, and so far I am not particularly impressed with the GPS accuracy and consistency. I have had quite a few different runs around the river where I apparently spend alot of time swimming! I had a 920XT before this, and actually had very few issues with the GPS track wondering off course.ANother one below.