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I have made some modifications to the original source as I was trying to get Channel Islands grid references working. As a result CI and XD prefixed squares now work, and there is an additional cigrtoll for WV and WA references, which may or may not work as expected. -- Chris Programs for conversion of latitude and longitude to national grids of Great Britain and Ireland, and vice versa K.D. Bennett Department of Plant Sciences University of Cambridge This package consists of four utility programs to make conversions from latitude and longitude to national grid co- ordinates for Great Britain and Ireland. They are not finely polished programs, but working utilities that do a job. There is a limited amount of checking on the input, for example, but bizarre input may produce bizarre results. The programs are: lltogbgr Converts latitude and longitude to co-ordinates of the Great Britain grid lltoirgr Converts latitude and longitude to co-ordinates of the Ireland grid gbgrtoll Converts co-ordinates of the Great Briatin grid to latitude and longitude irgrtoll Converts co-ordinates of the Ireland grid to latitude and longitude Each program can be run with no options, in which case it will prompt for input. Input grid values should be in the form "TL933937" (for Great Britain) and "C367821" (for Ireland): note that there are no spaces. Input latitude and longitude values on the command line take the form "1 34 56 55 32 10", where the first three values are degrees, minutes and seconds for longitude, and the second three values are degrees, minutes and seconds for latitude. All six values must be present, but decimals are allowed, and values can be zero: "1 30 30 55 30 0" is equivalent to "1 30.5 0 55.5 0 0". For longitudes WEST of Greenwich, the degree value should be entered as negative. If the lltoxxgr programs are run without options, they prompt for each of the six input values in turn. Conversion from longitude and latitude is by exact calculation using formulae and constants from the publications of the Ordnance Surveys of the two areas (see below). The reverse calculation is by successive approximation (make a guess, see how close it is, make a better guess, etc), and thus takes a little longer. Output has been tested against examples given by the Ordnance Surveys and against values from maps. I use these programs, and I have put some effort into checking their accuracy. But I cannot accept responsibility for any errors or problems caused by use of these programs. If you use the programs and find them useful, please let me know. If you use them and find them in error, I would also be interested to know. The programs are available by anonymous ftp to ftp-palecol.plantsci.cam.ac.uk, in directory pub/ll-to-gr. There is zipped package of the four MS-DOS executables, together with a copy of this README (ll-to-gr.zip), and a gzipped archive file (ll-to-gr.tar.gzip) of the source code, a makefile, and a copy of this README. The source code is ANSI C, with no frills, and should compile on any ANSI C compiler. References Ordnance Survey 1995. The ellipsoid and the Transverse Mercator Projection. Geodetic Information Paper No 1. Ordnance Survey, Southampton. Ordnance Survey 1950. Constants, formulae and methods used in Transverse Mercator Projection. HMSO, London. Ordnance Survey 1967. The history of the retriangulation of Great Britain 1935-1962. HMSO, London. Ordnance Survey 1953. Tables for the Transverse Mercator Projection of Ireland. Ordnance Survey Office, Dublin. Disclaimer Copyright (C) 1994 by K.D. Bennett. No portion of these programs may be reproduced for use by a commercial facility without express written consent of the author. This work is supported in part by the University of Cambridge. Neither the author, nor this institution, nor any of its employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the usefulness of any portion of this program. This copyright message and disclaimer must accompany any reproduced portion of this program.
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