GPS Discrepancies

[st599_uk]

I plonked 4 Garmin GPS on the bonnet of my Land Rover once whilst green laning. They all said different things. I knew where I was by the OS map (road junction scarily close to a cross of grid lines) . None were correct with nearly half a mile between the extremes.

What figures were you looking at? Grid Reference or Lat Long?

The spherical approximation of the Earth in use by GPS (WGS84) is different to that used by OS (OSGB36) and there's a discrepancy which can be 100s of metres.

[Jdsk]

I plonked 4 Garmin GPS on the bonnet of my Land Rover once whilst green laning. They all said different things. I knew where I was by the OS map (road junction scarily close to a cross of grid lines) . None were correct with nearly half a mile between the extremes.

What figures were you looking at? Grid Reference or Lat Long?

The spherical approximation of the Earth in use by GPS (WGS84) is different to that used by OS (OSGB36) and there's a discrepancy which can be 100s of metres.

OS's own explanation of the problem, I think that it's a pretty good attempt at using plain language:
https://www.ordnancesurvey.co.uk/docume ... ritain.pdf

Jonathan

[Mick F]

Ride complete, and three sets of stats ........... all different ............ surprise surprise!

I'll let the pictures speak for themselves.
September 2013 Garmin Edge 705
Today Garmin Edge 20 as well as Garmin Montana 600.
Absolutely identical ride today to September 2013. Same roads, same route, same hills.

Looking at the three profiles, the Edge 705 and the Montana look far more accurate, whereas the Edge 20 looks a bit "soft" and "wonky".