In article <trb3cj$9h5h$1@solani.org>, Joerg Lorenz <hugybear@gmx.ch>
wrote:

> >
> >> Once you narrow down the area to
> >> a radius of maybe 20 metres (which may be all you can know without
> >> differential GPS)
> >
> > gps is accurate to ~2m.
>
> AFAIK only for the US military forces.

for everyone.

selective availability was disabled 23 years ago, long before anyone
had a smartphone with a gps to find their car.

> For others 10m. But even that
> would be sufficient.

true.

In article <trb5d5$3r1o2$1@dont-email.me>, NY <me@privacy.invalid>
wrote:

>
> I was thinking of the accuracy of GPS indoors,

how often do you drive and park indoors?

Am 31.01.23 um 15:00 schrieb nospam:
> In article <trb5d5$3r1o2$1@dont-email.me>, NY <me@privacy.invalid>
> wrote:
>
>>
>> I was thinking of the accuracy of GPS indoors,
>
> how often do you drive and park indoors?

In big historic cities in Europe the normal case. Underground very often.

--
Gutta cavat lapidem (Ovid)

Am 31.01.23 um 15:00 schrieb nospam:
> In article <trb3cj$9h5h$1@solani.org>, Joerg Lorenz <hugybear@gmx.ch>
> wrote:
>
>>>
>>>> Once you narrow down the area to
>>>> a radius of maybe 20 metres (which may be all you can know without
>>>> differential GPS)
>>>
>>> gps is accurate to ~2m.
>>
>> AFAIK only for the US military forces.
>
> for everyone.
>
> selective availability was disabled 23 years ago, long before anyone
> had a smartphone with a gps to find their car.

Indeed:

From the early 1990s, GPS positional accuracy was degraded by the United
States government by a program called Selective Availability, which
could selectively degrade or deny access to the system at any time,[8]
as happened to the Indian military in 1999 during the Kargil War.
However, this practice was discontinued on May 1, 2000, in accordance
with a bill signed into law by President Bill Clinton.[9] As a result,
several countries have developed or are in the process of setting up
other global or regional satellite navigation systems.

--
Gutta cavat lapidem (Ovid)

In article <trbbjk$a689$1@solani.org>, Joerg Lorenz <hugybear@gmx.ch>
wrote:

> >> I was thinking of the accuracy of GPS indoors,
> >
> > how often do you drive and park indoors?
>
> In big historic cities in Europe the normal case. Underground very often.

that's not indoors, and underground car parks are also not that big
that a gps would even be needed. it's sufficient to remember which
floor.

On 31/01/2023 12:20, NY wrote:
> Agreed, but GPS can only get you so close. Once you narrow down the area to
> a radius of maybe 20 metres (which may be all you can know without
> differential GPS) you still need to know which of those cars is the one you
> hired.

If that's all you're getting perhaps a more modern GNSS device would help?
Make sure that all the services are switched on, especially GALILEO and GPS.
--
Cheers,
David
Web: https://www.satsignal.eu

Am 31.01.23 um 16:43 schrieb nospam:
> In article <trbbjk$a689$1@solani.org>, Joerg Lorenz <hugybear@gmx.ch>
> wrote:
>
>>>> I was thinking of the accuracy of GPS indoors,
>>>
>>> how often do you drive and park indoors?
>>
>> In big historic cities in Europe the normal case. Underground very often.
>
> that's not indoors, and underground car parks are also not that big
> that a gps would even be needed. it's sufficient to remember which
> floor.

You have no clue and you have never been in Europe.

--
Gutta cavat lapidem (Ovid)

In article <trbtie$ahds$1@solani.org>, Joerg Lorenz <hugybear@gmx.ch>
wrote:

> You have no clue and you have never been in Europe.

both wrong.

On 1/31/23 5:00 AM, Joerg Lorenz wrote:
> Am 31.01.23 um 13:44 schrieb nospam:
>> In article <trb13r$3qblf$1@dont-email.me>, NY <me@privacy.invalid>
>> wrote:
>>>
>>> Agreed, but GPS can only get you so close.
>>
>> close enough to find a vehicle.
>>
>>> Once you narrow down the area to
>>> a radius of maybe 20 metres (which may be all you can know without
>>> differential GPS)
>>
>> gps is accurate to ~2m.
>
> AFAIK only for the US military forces. For others 10m. But even that
> would be sufficient.

I thought they stopped Selective Availability. When I worked at
Magellan they suggested buying two commercial units and using
differential GPS (I think they claimed 2 feet then), but I never knew
how to do that.

I'm really sorry my free (every employee got one) brick-size unit died
before I even tried to use it -- I just had no reason at the time and
when I did years later it was dead.

--
Cheers, Bev
When you stop bitching you start dying.

"The Real Bev" <bashley101@gmail.com> wrote in message
news:trcqte$6l6a$1@dont-email.me...
> I thought they stopped Selective Availability. When I worked at Magellan
> they suggested buying two commercial units and using differential GPS (I
> think they claimed 2 feet then), but I never knew how to do that.

Ah, so is the technology the only limit the accuracy nowadays? I wasn't sure
whether Selective Ability still existed (even if no longer publicised) but
with a much smaller radius of error than before for non-military usage.

So if a normal GPS typically returns error >= 5 m, the only way to get a
more precise figure is to use differential GPS, cross-referenced to a
land-based receiver who position is known very accurately.

I find that GPS is good but not perfect: depending on reception conditions,
I may get

- a random error (a static object renders as a "spider" of successive
readings that vary about a mean point)

- a systematic error (the receiver's track closely follows the twists and
turns of a road, but is displaced in the latitude or longitude direction by
tens of metres, typically this effect comes and goes during a track)

That's with an Android phone in a car or mounted on the handlebars of a
bicycle, even in open countryside where *probably* many satellites are
visible to the receiver. The random error varies with the HDOP/VDOP readings
(as you'd expect) but the systematic error is just as likely with a good DOP
as a bad one. Results are better with the phone exposed (and probably
held/mounted horizontally) than with the phone in a pocket, in a vertical
orientation.

The fact that GPS works at all it a miracle; the fact that it is normally
good to +/- 10 m anywhere outdoors is a bonus. Hard to imagine the days
before GPS and satnav as an alternative/add-on to a paper map.