GeoTiff help for old map scan

Sorry to bother this list, but I'm looking for some help with writing
GeoTIFF.

Background:
I'm compiling a set of scans of out-of-copyright Ordnance Survey maps
(Popular edition approx 1920s and 30s). Which I want to make publicly
available (e.g. on geotorrent).

I'd like to create the files in geoTiff format, the problem is that
while I'm competent on the programming side I don't know what
parameters to use in the geotiff headers for each map. I've already
ortho rectified the scans, and can even project them into WGS84, but
I'd like to distribute each map unprojected.

Here's the information that I do have, can anyone help?

Projection system:
        Cassini-Soldner
                falseEastings = 0
                falseNorthings = 0
                Natural Origin Latitude = 53d 13m 17.274s
                Natural Origin Longitude = -2d 41m 3.562s

        Ellipsoid
                Airy 1830
                Major Axis:20923713 feet aka 6377563.396m
                Minor Axis:20853810 feet aka 6356256.909m

This is of course common to all the scans, an example scan would be:

                Sheet name: Popular Edition Sheet 44
                Cassini coordinates of the sides (feet)
                        N +48940
                        S -46100
                        W -3690
                        E 138870

                image dimensions:
                        width         8106 pixels .
                        height         5400 pixels

                one image pixel is
                        142560/8106 = 17.587 feet wide
                        95040/5400 = 17.6 feet tall

The slight discrepancy in the pixel dimensions happens because the OS
didn't always print the grid lines on the maps correctly.

Andrew Rowbottom

You might get some infos there
http://www.remotesensing.org/geotiff/geotiff.html on how to write geotiff
headers.
Bon courage!


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