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Phone GPS wonky

Old 02-20-24, 08:53 AM
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Phone GPS wonky

I've been using either Strava or RidewithGPS on my phone to let my wife track me during my rides. Recently, both have started showing some spurious points that drive her (and therefore me too!) nuts. While riding, the track show I'm following the road, and then there's a point a quarter mile off in a cornfield then back to the road in a sawtooth route, or it looks like I hiked into the woods and came back and kept riding. I sort of like these rides because I get a track a quarter to a third longer than what I actually rode. But SWMBO is afraid she'll run into rattlesnakes or bears if she has to come looking for me.

Subject phone is just under two years old, Samsung A23.

Is there a way to apply some more filtering to the phone's GPS, or force either app to use a sanity check to smooth the track out?
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Old 02-20-24, 09:22 AM
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You just have to face the fact that your phones GPS will face some challenges because of the way it's implemented in the phone. Along with how and when it establishes and shares your location. My wife and I have been sharing location with each other for over a dozen years now. And all of our phones have been subject to reporting my or my wife's location in the wrong place occasionally.

Perhaps ensuring that the apps you are using for this have permission to use your GPS whenever they want might help with some false reports.
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Old 02-20-24, 07:31 PM
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Originally Posted by pdlamb
... ... While riding, the track show I'm following the road, and then there's a point a quarter mile off in a cornfield then back to the road in a sawtooth route, or it looks like I hiked into the woods and came back and kept riding. ...
...
Is there a way to apply some more filtering to the phone's GPS, or force either app to use a sanity check to smooth the track out?
I do not know why this happens, but i have occasionally seen it over the years in some of my tracks. It only seems to happen when my GPS has not been used regularly for weeks.

I suspect that the GPS has old data in it for some of the satellite orbits, and as some satellites move further away and another satellite comes into view, if the data on the orbit is old for the one that just came into view, I suspect that it plots the location using old data with some error. This is only a guess on my part.

If my guess is correct, the best solution is have your GPS turned on more often to load more recent orbit data for all satellites into it.
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Old 02-20-24, 07:41 PM
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Originally Posted by Tourist in MSN
I do not know why this happens, but i have occasionally seen it over the years in some of my tracks. It only seems to happen when my GPS has not been used regularly for weeks.

I suspect that the GPS has old data in it for some of the satellite orbits, and as some satellites move further away and another satellite comes into view, if the data on the orbit is old for the one that just came into view, I suspect that it plots the location using old data with some error. This is only a guess on my part.

If my guess is correct, the best solution is have your GPS turned on more often to load more recent orbit data for all satellites into it.
I believe phone GPS’s are on whenever the phone is on. Cant get a signal if not outdoors, but they are still searching. If the phone is not outdoors enough, might not see whatever current position is on that moments constellation, thus may not be accurate. I would actually suspect poor reception of the signal, maybe a cheap receiver chip or whatever, thus loses the signal and generates a bad location.
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Old 02-21-24, 06:15 AM
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Originally Posted by Steve B.
I believe phone GPS’s are on whenever the phone is on.
No, the phones don’t have it on continuously. It would use way too much battery life.

You get location quickly because the phone can get approximate location from not just GPS like cell towers.

https://en.wikipedia.org/wiki/Assisted_GNSS
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Old 02-21-24, 06:22 AM
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Originally Posted by Tourist in MSN
I do not know why this happens, but i have occasionally seen it over the years in some of my tracks. It only seems to happen when my GPS has not been used regularly for weeks.

I suspect that the GPS has old data in it for some of the satellite orbits, and as some satellites move further away and another satellite comes into view, if the data on the orbit is old for the one that just came into view, I suspect that it plots the location using old data with some error. This is only a guess on my part.

If my guess is correct, the best solution is have your GPS turned on more often to load more recent orbit data for all satellites into it.
Phones can download the satellite data (“ephemera”) very quickly via other means. It doesn’t need to use the GPS for that. Your phone would likely need to have been isolated from other communications for a while for your explanation.

https://en.wikipedia.org/wiki/Assisted_GNSS
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Old 02-21-24, 06:30 AM
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Originally Posted by pdlamb
I've been using either Strava or RidewithGPS on my phone to let my wife track me during my rides. Recently, both have started showing some spurious points that drive her (and therefore me too!) nuts. While riding, the track show I'm following the road, and then there's a point a quarter mile off in a cornfield then back to the road in a sawtooth route, or it looks like I hiked into the woods and came back and kept riding. I sort of like these rides because I get a track a quarter to a third longer than what I actually rode. But SWMBO is afraid she'll run into rattlesnakes or bears if she has to come looking for me.

Subject phone is just under two years old, Samsung A23.

Is there a way to apply some more filtering to the phone's GPS, or force either app to use a sanity check to smooth the track out?
This complaint doesn’t seem common at all. It might be interesting to see the track.

If it’s “recent”, that suggests the phone hardware is not working properly.
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Old 02-21-24, 06:35 AM
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Originally Posted by Steve B.
I believe phone GPS’s are on whenever the phone is on. ....
I keep GPS on my phone turned off. Things like that, Bluetooth, etc., use more power than I care to use.
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Old 02-21-24, 07:00 AM
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Originally Posted by Tourist in MSN
I keep GPS on my phone turned off. Things like that, Bluetooth, etc., use more power than I care to use.
The phone has it turned off generally all by itself. It’s not correct that is on continuously.
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Old 02-21-24, 07:10 AM
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Military can occasionally scrabble and goof with GPS satellites signals.
This is Part of homeland security, and or other governments.
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Old 02-21-24, 07:19 AM
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Originally Posted by 1979schwinn
Military can occasionally scrabble and goof with GPS satellites signals.
This is Part of homeland security, and or other governments.
What he is describing doesn’t seem due to this at all.
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Old 02-21-24, 08:53 AM
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Originally Posted by 1979schwinn
Military can occasionally scrabble and goof with GPS satellites signals.
This is Part of homeland security, and or other governments.
I sure hope the Houthis can't disrupt GPS 400 miles from the Gulf Coast!
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Old 02-21-24, 09:46 AM
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My favorite GPS snafu was riding in downtown Manhattan, signal probably got bounced off of buildings and Strava showed a totally vertical rise of >900 feet. Looked like an elevator ride.
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Old 02-21-24, 10:13 AM
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I guess one other thing that you need to consider is where your phone is. Do you have it mounted next to a video camera or a flashing light. Many aren't a bother for GPS's but some are.
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Old 02-21-24, 12:16 PM
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Originally Posted by BTinNYC
My favorite GPS snafu was riding in downtown Manhattan, signal probably got bounced off of buildings and Strava showed a totally vertical rise of >900 feet. Looked like an elevator ride.
I have lost signal in between tall buildings in downtowns. Lack of a clear view of the sky can do that. And I can't recover until my GPS has clear signal from at least five or six satalites.

Parts of downtown Chicago have an elevated train, I think same with NY. I have lost signal under those in Chicago.
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Old 02-21-24, 12:40 PM
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Originally Posted by 1979schwinn
Military can occasionally scrabble and goof with GPS satellites signals.
This is Part of homeland security, and or other governments.
Yes, but so much public safety relies on it, it is unlikely that anything would get turned off or noticeably disrupted. Airplanes rely on it. Big ships rely on it. Business relies on the GPS signals for timing critical electronics and financial transactions. I think that the coast guard shut down their Loran system many years ago, leaving GPS as the sole way to see where you are in a harbor in fog or at night.

If the military messed with it, it would probably be to disrupt missile targeting, in which case I suspect most of us would be happy they messed with it.

I needed to get some land surveyed over a decade ago. Met the land surveys on site. They were using GPS. They said that the section corner in county records was off by 0.07 feet, or else the marker had moved. I told them that snow plows had moved the section corner monument before, likely would happen again. I was surprised at their level of accuracy, but they were less than a quarter mile from the differential station that they had set up at the town hall.

That said, short range jamming and spoofing is common on the battlefield.

Speaking of fog, that is the reason I bought my first GPS over two decades ago. If you are paddling your kayak towards an island, and accidently miss it, you could have a bad day.

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Old 02-21-24, 07:19 PM
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maybe it's the phone?

Disclaimer: I am not a GPS expert.

I had been using RWGPS with an Android phone for tracking my rides. After three or so years it just started to lose tracking randomly - like I'd have a straight line going over a bay or between places where there are no roads. I contacted RWGPS support (who were very helpful) and started troubleshooting. At first they had me download a "GPS Test" app which will test your phone's recognition of satellites - both in number and strength. So maybe give that a try.

Ultimately, the problem ended up being my phone: RWGPS' software would not play nicely with the older Android OS I had, which from memory was maybe 3 versions behind. I got a new phone and have had no problems since.

YMMV. Good luck.
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Old 02-22-24, 03:57 AM
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Originally Posted by HMJ
...
Ultimately, the problem ended up being my phone: RWGPS' software would not play nicely with the older Android OS I had, which from memory was maybe 3 versions behind. I got a new phone and have had no problems since.

YMMV. Good luck.
Thanks for the update. Maybe that is why Maps.Me stopped working well on my Android 7 phone? Phone works fine, but that app started mis-behaving. That said, I only used Maps.Me as a backup if my dedicated GPS stopped working, so not buying a new phone for a while.
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Old 02-22-24, 08:24 AM
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Yes, it happens to me, especially in Manhattan. Cloud cover also weighs in to create errors. It's usually not this bad. Sometimes it shows me surging to 50 mph, which I'm sure I never do on flat ground. Also, I'm sure I didn't ride through buildings or out onto the river.

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Old 02-22-24, 10:53 AM
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Originally Posted by noglider
Yes, it happens to me, especially in Manhattan. Cloud cover also weighs in to create errors. It's usually not this bad. Sometimes it shows me surging to 50 mph, which I'm sure I never do on flat ground. Also, I'm sure I didn't ride through buildings or out onto the river.

Tall buildings and rock canyons like Zion are notorious for deflecting GPS signals and causing multi-path errors. It’s well documented.
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Old 02-22-24, 01:31 PM
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You don't have a Garmin device that does livetracking? It still needs your phone to send the data to your spouse, but the GPS info is usually less prone to the weird times that phone location has you sitting somewhere for several minutes. Usually if they show you somewhere else, it's only for that one brief hit.
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Old 02-22-24, 03:39 PM
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Originally Posted by Steve B.
Tall buildings and rock canyons like Zion are notorious for deflecting GPS signals and causing multi-path errors. It’s well documented.
Yeah, I know. I just wanted to say it with my little quips and map. Whenever it happens, I chuckle.
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Old 02-26-24, 08:45 AM
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Originally Posted by pdlamb
I've been using either Strava or RidewithGPS on my phone to let my wife track me during my rides. Recently, both have started showing some spurious points that drive her (and therefore me too!) nuts. While riding, the track show I'm following the road, and then there's a point a quarter mile off in a cornfield then back to the road in a sawtooth route, or it looks like I hiked into the woods and came back and kept riding. I sort of like these rides because I get a track a quarter to a third longer than what I actually rode. But SWMBO is afraid she'll run into rattlesnakes or bears if she has to come looking for me.

Subject phone is just under two years old, Samsung A23.

Is there a way to apply some more filtering to the phone's GPS, or force either app to use a sanity check to smooth the track out?
hey
you can improve accuracy by turning on high accuracy or gps signal filtering within app settings.
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