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Posted by willem van deursen on January 18, 2006, 3:04 pm
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Hi Oliver,
almost any GIS can do this for you, but if you want to build it yourself, one of
the approaches could be:
1. Find and download a shapefile for Denmark. Shapefiles are the de facto
standard for storing vector information in the GIS world. I googled for "Denmark
Shapefile" and this is one of the sites I found:
http://www.vdstech.com/map_data.htm
(Make sure that you get a shapefile with lat/lon projection, I didn't check the
data on this site)
2. Find a convertor to go from shapefile to text. Again: google!
Shp2txt on http://www.obviously.com/gis/shp2text/ seems to do what is needed,
but I didn't check
3. Find the algorithm for pointinpolygon (Google:
http://astronomy.swin.edu.au/~pbourke/geometry/insidepoly/), implement this and
ready to go!
But, as I said before, if you don't want to program it yourself, any GIS will do
this for you.
Regards
Willem van Deursen
martin.madsen@safetrack.dk wrote:
> Hi,
>
> I am new to this board and hope some of you GIS gurus can help me. I
> need to determine if a given latitude and longitude is inside or
> outside of Denmark and probably other european countries. For this i
> have thought about drawing a polygon which defines the borders of
> Denmark, and then see if my latitude and longitude is inside or outside
> of this Polygn. Is this the right apporach, and where do i get my hands
> on data like that ? I have tried with the data from this site, but
> there does not seem to be a collection of latitude and longitude coords
> that would help me 'draw' my polygon.
>
> Thanks for any help.
>
> Regards,
> /Oliver
>
--
Willem van Deursen, The Netherlands
wvandeursen_nospam@nospam_carthago.nl
replace _nospam@nospam_ for @ to get a valid email address
www.carthago.nl
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