There is a software tool (command line only, I am afraid) called geod, which is part of the proj software suite (http://proj.maptools.org/). This will allow lines to be extended on particular bearings and distances, and return a list of equally spaced points over which the line passes. The line it uses is a great circle, not a rhumb line, but I doubt if that matters to your user. This tool is regarded as the "best" for geodetic and great circle calculations.
If the distances concerned are more than a few kilometres and the accuracy required is high, then your user needs to think very hard about the nature of the line and what exactly he/she means by "passes over". Is the user aware, for example, that the datum of OS maps has changed significantly over recent years?
Paul
>>> [log in to unmask] 10 May 2005 14:40:38 >>>
Dear lis-maps and carto-soc
Can anyone help with this enquiry? Reply to me or to the list and I will
pass any answers on to the enquirer.
Many thanks
Anne
>I was wondering if you or any of your colleagues could possibly point me
>in the direction of a suitable piece of mapping software?
>I've found something on the net -
>http://www.movable-type.co.uk/scripts/OSGridDist.html - that will
>calculate the distance and bearing between two OS grid points, and very
>useful it is too. But what I want to be able to do is to be able to
>measure intangible lines between intangible sites in the landscape (hope
>this is making sense) - i.e., extend a line or lines into the landscape
>and see what OS grid points it crosses.
>
>I've been Googling to try and find such a piece of software, but,
>evidently, I haven't been using the right search terms! I don't know
>whether you could possibly come up with any suggestions ... ?
Anne Taylor
Head of Map Department, Cambridge University Library, West Road, Cambridge
CB3 9DR
Tel: 01223-333041. Fax: 01223-333160. email: [log in to unmask]
http://www.lib.cam.ac.uk/maps/Home.htm
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