[mapserver-users] pixels do not match data

Florin A. pianosnake at gmail.com
Sat Apr 26 16:44:49 EDT 2008


Hi,

I have a postgis layer in UTM zone 13 with squares that are exactly
one hectare size (100 by 100 meters).  I want the output image to have
1 pixel 1 hectare correspondence.   Any ideas on how to do this? The
image coming back is wrong. There are 4 pixels for every 1 hectare, as
if the pixels and the lines didn't exactly overlap.

Here's what I've done so far:
-set width and height of my image to 1/100 of the width and height of
the layer. made width and height values even (seems to give back the
right cell size of 100).
- I have units defined as meters and the projection defined as 26913
in the mapfile.
-cellsize comes back as 100, which is good.
-extent comes back as what i defined (but only when i make the image
size even numbers)
-made the image size even numbers, both 1 above my values, and 1 below
-my cell boundary coordinates in the postgis layer are factors of 100.
i checked all of them
-in postgis i used the snaptogrid function to make sure all the cell
vertices were factors of 100
-defined projection with both epsg code, and by listing out the attributes

If I increase the image size it gets closer and closer to what I want,
but I'm hitting against the 2048 width limit and I'd rather keep the
image size small and where it ought to be.  I'd appreciate any advice,

Thanks,


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