I've recently added a few new sites in Derbyshire and when I check there position in the Google Maps viewer there is a error and the sites in Google are plotted about 100m to the east / northeast of their associated grd ref. I've also noticed the same error in some of the older sites.

I'm not sure if this is local to the Derbyshire area or more widespread

The link to the 25,000 scale Streemap appears to be ok and plots the sites in the right place

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Google probably uses WGS-84 (as used by global GPS), whereas Streemap probably uses OSGB36 which the OS uses. See http://www.movable-type.co.uk/scripts/latlong-convert-coords.html 

Cheers,

Robin

I was thinking it was probably some co-ord system, I've noticed something similiar on some sites that convert OS in to and from long / lat.

Initially the error was a little annoying because the co-ords I use are generated using a GIS package, but the co-ords it gave me are ok (i.e grid lines match up)

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Hi LeeW

I suspect it's because the Google maps plot off the 6 figure Landranger reference, e.g. AB123456 for UK mines, therefore all it does is place the mine with a 100m square.

For international mines it uses lat/long which is rather more accurate.

Next year (early on hopefully) I want to set aside a week to rip out a lot of site code to do with mine searching and plotting (all 5 years old now) and re-write it to make it a lot more searchable, a lot faster and a lot easier to use. Looking at mapping 'issues' will be part of this, including fixing the long standing issue of 'mines near' where the mine is close to the edge of the map sheet. Probably this will involve using lat/long for all mapping / plotting / proximity functions with lat/long being worked out from grid reference if not already entered.

In fact I'm intending to re-write quite a lot of the site, doing some of the groundwork at the moment, but core stuff like searching for mines and photos and the forum will be the core of the make it faster / make it easier to use re-write.

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Good on you Simon.
Plotting in decimal lat/long is great for chasing places on Google Earth, hand held gps etc. et al
Be great if you can find the time to make that change
Thanks

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In doing that, will it make the pointers on Streetmap wrong?

No!

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Glad to hear that Simon! None of these other maps are a patch on OS maps (even though they are not as good as they used to be).