[mapserver-users] Re: Missing row of pixels in MapServer generated tiles

[Roger André]

One thing I did notice is that my EPSG file definition for "Spherical
Mercator" is missing a parameter, "+nadgrids=@null".  I'll test tomorrow to
see if adding it to the definition removes the problem.
--


On Sat, Oct 18, 2008 at 7:25 PM, Roger André <randre at gmail.com> wrote:

> This is probably more of a TileCache question, than a MapServer one, but I
> figure one of you may have had the same issue in the past.  I'm using
> MapServer to feed TileCache a fairly large GeoTiff with global extents,
> which I'm then displaying in Google Maps as a tile layer.  This has worked
> well in the past, but now I'm encountering a weird problem.  Some of my
> tiles are being rendered by MapServer with a row of pixels missing on the
> bottom of the image.  So for example, in Zoom Level 2, all of the 0.png
> tiles will be 256 x 256 pixels, but row 256 will not contain data from my
> global image, but instead will be set entirely to whatever background color
> I have set in my Mapfile. The problem appears in multiple, but not all, Zoom
> levels, and at different geographic locations, but always at the bottom row
> of a tile.
>
> The source image doesn't have the lines in then, so I have to believe that
> the "dead" row is an artifact of the rendering process.  My seed image is in
> lat/lon WGS84, and the tiles are being requested in EPSG:900913.  The
> reprojection seems to be working correctly, insofar as image lineup with
> Google Maps seems to indicate.  If I take the seed image and create a very
> reduced resolution version of it, then run it through TileCache, I don't get
> any lines.  So it seems like the lines *might* be a result of downsampling,
> but since they're not present at the bottom of every image, I'm not
> convinced that's the problem.
>
> Oh, and I'm using the GD driver.
>
> Any ideas?
>
> Roger
> --
>
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