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From: The Real Bev <bashley101@gmail.com>
Newsgroups: comp.mobile.android
Subject: Re: Erratic GPS
Date: Tue, 25 Jun 2024 08:25:33 -0700
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On 6/24/24 4:45 AM, Kyonshi wrote:
> On 6/24/2024 2:24 AM, Ralph Fox wrote:
>> On Sun, 23 Jun 2024 13:59:56 -0700, The Real Bev wrote:
>>> On 6/23/24 1:21 PM, Andy Burns wrote:
>>>> The Real Bev wrote:
>>>>
>>>>> Every once in a while her location will shift by as much as half a =
mile
>>>>> and then shift back within minutes.=C2=A0 Is there any possible cau=
se for this
>>>>
>>>> Losing view of the satellites and falling back to cell tower or wifi=

>>>> location?
>>>
>>> Standing still.  This isn't a quiz, I really want to know.
>>=20
>>=20
>> GPS location relies on signals from GPS satellites being direct *line
>> of sight*, and comparing the timing of signals from multiple GPS
>> satellites to extremely fine accuracy (a nanosecond, the time it takes=

>> a signal to travel one foot).  It is not "Harry Potter" magic.  If any=

>> GPS satellite signal is not line of sight, this will throw the
>> calculation out.
>>=20
>>=20
>> If your daughter is anywhere where her device could be using a GPS
>> satellite signal that is reflected off a building, wall, cliff,
>> or otherwise not direct line of sight, then this is not surprising.
>>=20
>> If your daughter is anywhere where her device does not get direct
>> *line of sight* signals from at least 4 (four) GPS satellites, then
>> this is also not surprising.
>>=20
>> If your daughter was outdoors in a wide open plain, not under a roof,
>> not next to a building, cliff, or wall higher than her device, not in
>> a canyon, no tall buildings, hills, or mountains nearby, then and only=

>> then I would guess an issue on one of the GPS satellites.  Such issues=

>> are generally notified; see
>> <https://en.wikipedia.org/wiki/Notice_Advisory_to_Navstar_Users>.
>>=20
>> GPS was originally designed for nuclear submarines in the middle of
>> the ocean, where GPS signals will always be line of sight and
>> at least 4 (four) GPS satellites will always be in line of sight.
>>=20
>>=20
>> This *is* a pot-luck quiz when we do not know what kind of place your
>> daughter is in.
>>=20
>> Although your daughter may be standing still, the GPS satellites are
>> not.  GPS satellites are NOT geostationary.  GPS satellite signals
>> do move.
>=20
> I also noticed that Google's quality of their GPS data seems to have
> gone down lately. I started doing longer extended walks about two years=

> ago, and noticed that over time the timeline Google provides has become=

> somewhat unreliable in tracking how much I walked. It was better before=
,
> getting at least a rough estimate of the distance I walked through the
> city. The last few months it has stopped being reliable, with large
> sections of my walk missing.
> This doesn't seem to be a GPS issue, as using 3rd party GPS apps
> provides much better tracking where I am.

I started using Ski Tracks when it first became available.  I think it=20
costs $1.50 now, but well worth it.  It tries to frame everything in=20
terms of ski runs (sometimes funny), but the files it saves are fine and =

can be dumped into google earth -- which is way less valuable than it=20
might be.  AND it's not battery-hungry like OSMand.

In fact google maps could be way better than they are.

--=20
Cheers, Bev
    If you are going to try cross-country skiing,
    start with a small country.