Inaccurate position when stationary

wildesy · Occasional Visitor Joined: Mar 31, 2005 Posts: 6

Hi all - any help would be appreciated

I have just received a BT-77 BT GPS connected to TomTOm mobile on smart phone or laptop.

When testing i thought i was consitsantly 50 to 100m north of my actual position, even when stationary (for hours) and with 8 or more satelites showing.

I positioned by GPS next to a freinds wired tomtom gps and compared positions.

East Mine 054424 His 054434 (might have missed a decimal point here)
North Mine 51.32825 His 51.32933

Doing some really rudimentry testing we reckon this confirms my GPS is wrong.

Am i right or am i talking rubbish?

Can i reset the GPS using the PC utility (which has loads of options but no instructions) or return for an exchange.

Thanks in advance?

Skippy · Posted: Mon Apr 04, 2005 12:54 pm Post subject:

Hmm. I presume you were parked on a road at the time? Is is possible that one of the GPS units had "snap to road" switched on and that caused the position error?

Do you get problems with intersections being badly misaligned or does it work OK when you are on the road.

Other than that, perhaps you could try and find a professionally surveyed landmark and check your position against that to be 100% certain.

Sounds like your GPS might be broken. Crying or Very sad

_________________
Gone fishing!

wildesy · Occasional Visitor Joined: Mar 31, 2005 Posts: 6

Skippy, thanks...

We were parked in a carpark and I assume the snap to road function would only change the map viewed position and not the actual gps coordinates as given by tomtoms configure gps function.

If im travelling north/south im shown on the right road however my position is either before or behind my actual position. If travelling east west im always shown north or south of the road by about 60m. EG if travelling east along an eastward rooa my position is shown 60m north of the road!

I think it must be the gps.

Skippy · Posted: Mon Apr 04, 2005 6:19 pm Post subject:

Privateer · Posted: Mon Apr 04, 2005 9:27 pm Post subject:

Hi,

I don’t know the BT-77 BT unit, you say that you have a PC utility. Does that utility have any options for displaying and changing the “Map Datum”? If it does, make a note of the current value of the Map Datum and change it to WGS84, which is what most electronic maps use.

It’s another straw to clutch at. Wink

I can’t guarantee that it’ll work but using the wrong Map Datum (e.g. Ordnance Survey 1936) can place you 50 or 100 metres away from the correct position.

Regards,
_________________
Robert.
iPhone 6s Plus, iOS 14.0.1: iOS CamerAlert v2.0.7
TomTom GO Mobile iOS 2.3.1; TomTom (UK & ROI and Europe) iOS apps v1.29
Garmin Camper 770 LMT-D

wildesy · Occasional Visitor Joined: Mar 31, 2005 Posts: 6

Its set to WGS84 by default.

I think it must be faulty, i'll send it back

Privateer · Posted: Mon Apr 04, 2005 10:02 pm Post subject:

Hi,

I’ve just had another thought. Are there any "off set" parameters that have values other than zero?

Regards,
_________________
Robert.
iPhone 6s Plus, iOS 14.0.1: iOS CamerAlert v2.0.7
TomTom GO Mobile iOS 2.3.1; TomTom (UK & ROI and Europe) iOS apps v1.29
Garmin Camper 770 LMT-D

wildesy · Occasional Visitor Joined: Mar 31, 2005 Posts: 6

To late to check as its in the post

I'll update you when i get the replacement

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