I seem to remember sometime ago a discussion about this, but am unable to find it. Does anyone know the answer as to whether this is based on WGS84?I ask this as I have noted the following:I position myself over a South of England landmark that is directly on the coast and note the Lat/Lon. When I check that same position on a marine chart (Admiralty) I am placed well over the sea.Thanks in advance for any thoughts.David

Yes it's WGS84.

At the moment you will only find the WGS84 Lat and Long graticule printed on aviation charts. OS are not going to convert their maps to suit and that means many others won't either.If you go to the OS site you can get an OSGB36 to WGS84 conversion file in Excel. The difference is roughly 500ft in S. England.

Thanks for the confirmation. I guess that MS are not too accurate in the coastlines sometimes - maybe it depends on the tide....Incidently, all marine charts are also (or will be) WGS84.David

From looking at the offset in FS I would guess that the coastline data is still OSGB36. It doesn't work well with a mesh designed to WGS84!Because the coastline has the trick of forcing mesh down to sea level the result can be very marked. In the UK you will find that mesh is truncated on the east coast because the coastline is 500ft inland. On the west coast the opposite happens and you may notice 500ft deep beaches at the bottom of cliffs.You can check this out if you have third party mesh. Just deactivate NWEurope and see the difference!

Coastlines are also WGS84, everything in FS2002 is.The coastline data is based on the Digital Chart of the World data, which only is accurate to 2km. This is hugely inaccurate and this is where this error comes from. For more accurate detail you have to pay, whereas DCW data is freely available.I've tried it, put WGS84 DCW data over FS2000 data and bingo 100% match. The bad news is that the inaccuracies of DCW aren't coordinate system related at all. I tried to match to more accurate data by shifting and rotating. Once I had a perfect match in one region, it was much worse in other regions. There is no systematic error in the DCW data, it's just bad...Cheers, Christian