GPS Problems

Nige · Dec 31, 2004

Just got a Garmin sat-nav system & it's a couple of miles out. I know the earthquake caused some problems
but I didn't think it was that far out?

Anyone else got any ideas & if anything can be done?

Ta

Nige

--
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Paul - xxx · Dec 31, 2004

Nige composed the following ...
> Just got a Garmin sat-nav system & it's a couple of miles out. I know the
> earthquake caused some problems but I didn't think it was that far out?
>
> Anyone else got any ideas & if anything can be done?

It's quite a while since I had a new one, I don't have any at all now, but I
seem to remember having to synchronise (or some other technical term) the
map to the signal. Ours was a company sourced Autoroute map and (I think)
Garmin based GPS receiver, all done on laptop .. so may be well out of date.

Garmin site has loads of manuals etc to download ...

--
Paul ...
http://www.4x4prejudice.org/index.php
(8(!) Homer Rules ...

"A tosser is a tosser, no matter what mode of transport they're using."

Dougal · Dec 31, 2004

> Just got a Garmin sat-nav system & it's a couple of miles out. I know the earthquake caused some problems
> but I didn't think it was that far out?
>

I can't comment on the latest ones with pre-installed maps but if you
are relying on the OS grid reference as a means of determining accuracy,
check your datum defaults.

I can't remember by how much but the default(?) WGS84 datum gives a
considerable error.

Assuming UK use, you want Ordnance Survey GB as the Map Datum, British
Grid as Position Format. Look in the Navigation sub-menu of the main menu.

David

Richard Brookman · Dec 31, 2004

So Dougal was, like

>> Just got a Garmin sat-nav system & it's a couple of miles out. I
>> know the earthquake caused some problems but I didn't think it was
>> that far out?
>
> I can't comment on the latest ones with pre-installed maps but if you
> are relying on the OS grid reference as a means of determining
> accuracy, check your datum defaults.
>
> I can't remember by how much but the default(?) WGS84 datum gives a
> considerable error.
>
> Assuming UK use, you want Ordnance Survey GB as the Map Datum, British
> Grid as Position Format. Look in the Navigation sub-menu of the main
> menu.
> David

Yup, had same problem when I got my Garmin a few years ago. Out by about ¾
mile compared to an OS map. The units are all set to WGS84 as the default
datum. Change that to something like OSGB and it'll be spot on.

--

Rich

Pas d'elle yeux Rhone que nous

TonyB · Jan 1, 2005

>
> Yup, had same problem when I got my Garmin a few years ago. Out by about
¾
> mile compared to an OS map. The units are all set to WGS84 as the default
> datum. Change that to something like OSGB and it'll be spot on.
>
That's correct but the latest marine charts use WGS84 so if your GPS is
primarily intended for marine use it'll be pre-set to that. Change the datum
as suggested and it'll be fine.
TonyB

Ian Rawlings · Jan 2, 2005

On 2005-01-01, TonyB <[email protected]> wrote:

> That's correct but the latest marine charts use WGS84 so if your GPS
> is primarily intended for marine use it'll be pre-set to
> that. Change the datum as suggested and it'll be fine. TonyB

Also it wasn't clear if the OP was using his GPS in conjunction with a
piece of route-finding software, if so then he'd need to set it to use
one of the WGS datums. When I am using my ETrex with OS maps I switch
to OSGB datum, when using it with my PDA-based route finding software
I switch to WGS72 or sommat.

Have a look on www.gps.gov.uk, useful information there, especially
the following link and sub-pages;

http://www.gps.gov.uk/additionalInfo/GPSandOS.asp

--
For every expert, there is an equal but opposite expert

Richard Brookman · Jan 2, 2005

So TonyB was, like

>> Yup, had same problem when I got my Garmin a few years ago. Out by
>> about ¾ mile compared to an OS map. ***The units are all set to WGS84
>> as the default datum***. Change that to something like OSGB and it'll
>> be spot on.
>>
> That's correct but the latest marine charts use WGS84 so if your GPS
> is primarily intended for marine use it'll be pre-set to that. Change
> the datum as suggested and it'll be fine.
> TonyB

That was what I said, wasn't it?

--

Rich

Pas d'elle yeux Rhone que nous

TonyB · Jan 3, 2005

> >> Yup, had same problem when I got my Garmin a few years ago. Out by
> >> about ¾ mile compared to an OS map. ***The units are all set to WGS84
> >> as the default datum***. Change that to something like OSGB and it'll
> >> be spot on.
> >>
> > That's correct but the latest marine charts use WGS84 so if your GPS
> > is primarily intended for marine use it'll be pre-set to that. Change
> > the datum as suggested and it'll be fine.
> > TonyB
>
> That was what I said, wasn't it?
>

As I acknowledged. I was just trying to explain why they are not always set
for land use.
So there.
TonyB

Richard Brookman · Jan 2, 2005

So TonyB was, like

> So there.

--

Rich

Pas d'elle yeux Rhone que nous

Reg · Jan 2, 2005

"Nige" <[email protected]> wrote

> Just got a Garmin sat-nav system & it's a couple of miles out. I
know the earthquake caused some problems
> but I didn't think it was that far out?
>
> Anyone else got any ideas & if anything can be done?

What GPSr is it?

The earthquake has changed a few earth parameters, but with a
commercial GPSr, you probably wont notice it.

If it is not one of the newer Garmin GPSrs like the 2610, which can't
change the datum from WGS84 (default) to OSGB36, then this could be
set incorrectly.

If you have changed the unit of display from Lat/Long to BNG, then you
also have to change the datum on the older models. Some newer ones
have these two options merged into one, which would only cause you
problems if using an OS sea going map and OSGB36/Lat/Long.

Restricting the GPSr from 'seeing' the satellites can also reduce the
accuracy - like having a heated windscreen.

But an error of 2 miles indicates a major problem as the causes
mentioned above will only give error of up to about 300 yards. Setup
errors will not give errors of 2 miles.

Reg.

Mark Gardiner · Jan 14, 2005

My Garmin Emap is set to WGS84 and has not shown any positional errors in 3
years. I can plot my back garden on an OS25 map to within 2 metres, when using
an external aerial.I would suspect the integrity of the loaded maps if there is
much of a difference between WGS84 and OSGB.

Mark

2002 KLR650 C7,
1989 KMX200,
1981 PE175 X, now sold,but without memories
1971 Range Rover ( mostly in bits! )
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GPS Problems

Nige

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Paul - xxx

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Dougal

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Richard Brookman

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TonyB

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Ian Rawlings

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Richard Brookman

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TonyB

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Richard Brookman

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Reg

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Mark Gardiner

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