Is there an easy way to find the tile reference for a given area. I
have found what I need so far by trial and error, but with 400 tiles
it can be a bit of a pain.
--
Philip Stubbs
Philip,
A quick sketch on the method to go from tile filename to coordinates.
Say we use the filen//ame su85se.tiff. The "su" part, the "85" part and
the "se" part each give a different northing and easting offset. The
must be summed to get the final bottom left corner position.
The first offset is basically coarse grid letter offset and is found in
a look up table. The codes are arranged like this:
http://en.wikipedia.org/wiki/File:National_Grid_for_Great_Britain_with_central_meridian.gif
The "85" is an intermediate offset, I think it is 8x10000 metres east
and 5x10000 metres north.
The final code can be se, sw, ne, nw for a fine tile offset. The "n"
sheets are offset north by 5000m. The "e" sheets are offset east by 5000m.
Each tile is 5000m by 5000m, as far as I remember so you can get the
coordinates of the other corners.
Re-reading your question, I guess you really want the inverse of what I
just described? I hope that helps a little anyway.
TimSC
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