[Gvsig_english] Creating density raster/isolines out of point layer

[Benjamin Ducke]

The lat-long system makes calculating basic geometric properties like
"area" hard, because the simple assumptions of cartesian space do not
hold and everything must be based on the much more complex geodetic
distance. In addition, you have non-intuitive effects such as
wrap-around to consider.

For that reason, many analytical GIS modules won't work on lat-long
data.

Blame Earth for her weird shape.

Ben

davk wrote:
> Hi community,
> 
> sorry for not answering your last question. It worked fine by converting the
> raster map to polygons.
> I just want to mention two problems that occured to me:
> 
> 1) The raster density calculation didn't work on a Lat/Long projection, but
> on a projection similar to UTM. Is it too hard to program it for Lat/Long or
> was it bugged for me?
> 2) For the outputted raster density map only 1 color band was shown in
> gvSIG. Pixel transparency didnt' work with it. With other .tif files where 4
> bands were shown (3 for the colors and another) it worked perfectly. Do I
> have to convert the outputted raster density map before using pixel
> transparency on it?
> 
> Probably these are stupid questions. 
> Thanks for your help.
> 
> greetings davk
> 


-- 
Benjamin Ducke
Senior Applications Support and Development Officer

Oxford Archaeology Ltd
Janus House
Osney Mead
OX2 0ES
Oxford, U.K.

Tel: +44 (0)1865 263 800 (switchboard)
Tel: +44 (0)1865 980 758 (direct)
Fax :+44 (0)1865 793 496
benjamin.ducke at oxfordarch.co.uk




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