[Qgis-user] Problem with the join attributes by location ftools plugin

[Lionel Roubeyrie]

Hi all, hi Carson,
Needing to sum some pollutants concentrations stored in a polygon
shapefile, I come across a big problem with the "join attributes by
location" of the ftools plugin.
My source polygon shapefile is for simplification a regular grid, and
the target shapefile too, with exactly the same limits (in fact the
source shp is based on the target on). When calling the plugin, it first
complains about source and target are in differents CRS, which is false
(I use EPSG 27572), and after computation using the "sum summary of
interesting features", the results are somewhat unexpected, because in
each target polygon, the sum represents the sum of the contigous sources
polygons, and not just the sources polygons INSIDE the target one.
To be clear you can see in the attached file an example where the
sources concentrations values are in normal font (one value by polygon),
and in bold the resulting sum in the targets polygons (where normally
expecting the same values as in the sources).
I think there's missing a test in the plugin to select values if they
are strictly inside the target.
Hope there's a simple solution, I really need the values :/
Thanks
PS : without this problem, the ftools plugin is really a nice tool. Good
job Carson :)

-- 
Lionel Roubeyrie
chargé d'études
LIMAIR - La Surveillance de l'Air en Limousin
http://www.limair.asso.fr
-------------- next part --------------
A non-text attachment was scrubbed...
Name: ex.png
Type: image/png
Size: 19845 bytes
Desc: not available
URL: <http://lists.osgeo.org/pipermail/qgis-user/attachments/20090331/63a72f27/attachment.png>