[R] intersecting polygons and conversion from decimal degree to km

[Roger Peng]

Intersecting polygons is a fairly non-trivial task, one which I was
confronted with a few years ago.  Luckily, Alan Murta has written a very
nice C library which can be downloaded at

http://www.cs.man.ac.uk/aig/staff/alan/software/

A little while back I wrote an R interface to this library which is fairly
straightforward to use but it's a little rough and ready.  The good
thing is that Murta's library is *very* fast.  It can
intersect/difference/union polygons with over a thousand points very
quickly. 

If you're interested in my R package please email me privately.

-roger
_______________________________
UCLA Department of Statistics
rpeng at stat.ucla.edu
http://www.stat.ucla.edu/~rpeng

On Fri, 24 May 2002, Renaud Lancelot wrote:

> Dear all,
> 
> 1. How can I compute the intersecting area between 2 polygons ?
> 
> 2. I have polygons with coordinates in decimal degrees (i.e. 13 deg 30
> min = 13.5 decimal degrees). I want to compute their area and get the
> results in square meters or square kiometers. Can anyone give me a
> conversion coefficient or a pointer where I can find this information
> (sorry for this off topic question) ?
> 
> Thanks in advance,
> 
> Renaud
> 
> -- 
> Dr Renaud Lancelot, vétérinaire
> CIRAD, Département Elevage et Médecine Vétérinaire (CIRAD-Emvt)
> Programme Productions Animales
> http://www.cirad.fr/presentation/programmes/prod-ani.shtml (Français)
> http://www.cirad.fr/presentation/en/program-eng/prod-ani.shtml (English)
> 
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