Sometimes GPS devices will briefly lose contact with satellites for a variety of reasons. It can be as simple as interference caused by buildings. This can throw off your location for short periods of time by many meters, and then as reception improves, the track regains accuracy.
Errors like these just happen sometimes. There’s probably no way to know the precise cause, and it certainly isn’t worth trying to analyze.
You know how sometimes you may be in your car listening to the radio, and it fades out a little bit? Then you let your foot off the brake, you move forward like a foot, and the radio is clear again? It’s like that. The signal was off a little for some reason, then it got better. The only difference is that you have a visual representation of the error to stare at.
I had problems with Uber location yesterday afternoon. It didn’t pinpoint my location, and didn’t properly track the driver coming to pick me up, it showed he was 15 minutes away when he was standing right in front of me. Something was definitely wrong with the GPS.
Do you have “high accuracy with GPS” on all of the time, or do you use other, less accurate, location features? Under the “location” settings on my phone, I have it set to “battery saving”, which uses cell network and known wifi networks to ascertain my location. So, if I look at my trip history, it shows my location off by a modest amount at times as (I presume) it figured out where I was by cell tower triangulation.
I went to the gym & used the Stairmaster. I usually do this while wearing my GPS watch on so that I can log duration & HR of the workout. I typically turn GPS off since I’m not physically changing location outside the parameters of the machine (approx. a box of 2’ x 2’ x 6"). Doing such not only uses less battery but doesn’t give me artificially low / BS readings (in 20 mins, you moved 10’ :rolleyes:). For whatever reason, I forgot to turn the GPS off last week.
[ul]
[li]The white rectangular box is the gym.[/li][li]The blue arrow is where the equipment is within the gym.[/li][li]My entire workout was on the equipment; started the watch when I started the workout & stopped the before I got off of the equipment. [/li][li]The building is large plate glass windows & cinder block, IOW, not so easy to pass thru.[/li][li]The track of my workout shows me in the parking lot numerous times, as well as twice going in & out of the walls of the supermarket next door. :smack:[/li][/ul]
There’s also a well-known sports-tech blogger that tests new equipment; he’ll run 4 different GPS devices at a time for a run/bike ride. He overlays the data so you can see accuracy of the device being tested. For the most part they line up, but then every once-in-a while, one will wig out & put him in the river as opposed to on the trail next to it. Sometimes, this is the tried & true one he knows is accurate.
In short, GPS is not as perfect as we would like it to be. When I go mountain biking the GPS data will often show my track as being some distance off the trail. If I ride the same trail several times sometimes each track is on top of the other and sometimes there is some drift in the calculated position.
I tried to use one of those GPS tracker apps for my 12 mile bicycle commute into Seattle once. It went … poorly. Apparently I took a 100mph detour off the I-90 bridge bike trail into the middle of Lake Washington. Needless to say the stats on my ride were less than accurate. Also, I think I would have remembered that.
A dedicated GPS cycling computer seems more reliable than a phone app, but is still less than perfect. I mainly have minor problems and only when mountain biking through forest. My road rides get tracked very well.
GPS works by measuring the difference in distance from multiple satellites in the sky, by measuring the time difference of the signals from the satellites. This works well if the GPS receiver has a clear, unobstructed view of at least 3 satellites in the sky. But when you try to use it indoors, it often gets an indirect signal, e.g. reflected by a nearby building. This fools the receiver into thinking it’s further away from that satellite (because the signal from that satellite has to travel further than it would if there was a direct path). This is mainly why the location jumps around when indoors. This is usually called “multipath” error.
Once you exit the building, it may take some time to reestablish the correct location. Which is why the track skips over the first part of your trip right after you leave the establishment.
