[mapserver-users] What resourse blocks any bigger GeoTIFF output from WCS?

[Rahkonen Jukka (MML)]

Hi,

I started to experiment with WCS 2.0.1 with Mapserver 7.1-dev and I managed to get WCS to work rather easily. However, I can only get data with rather small GetCoverage requests when using image/tiff format.

My environment:
MapServer 7.1-dev which I installed from the 32-bit Windows binaries from gisinternals http://download.gisinternals.com/sdk/downloads/release-1600-gdal-mapserver.zip. For installation I used existing MS4W installation by making a new cgi-bin directory where I dropped the new binaries (dll files and mapserv.exe).
My computer is 64-bit Windows 7 with 8 GB of memory. I am stuck with 32-bit Mapserver because using MS4W on the bottom is the only way to install that I can handle.

Output is successful when the resulting image is 8000x8000 pixels (192 MB) but if I try to get an image with 10000x10000 pixels (300 MB) I am receiving an error:

<ows:ExceptionText>msWCSWriteFile20(): General error message. msSaveImage() failed
msSaveImageGDAL(): General error message. Failed to create output GTiff file.
TIFFAppendToStrip:Write error at scanline 6500
I have no problem at all with output size of 12000x12000 pixels if I use image/png or image/jpeg.

If I play with subset ranges I can see that the GeoTIFF write error happens at different scanlines. It makes me think that it could be some memory problem. But how could I give more resources for GDAL so it could make its job?  I have not yet thought how big images I will need from WCS but lets say the aim is at 50000x50000 pixels which would make 7.5 gigabyte GeoTIFF as an uncompressed, 8-bit, 3-band image.

-Jukka Rahkonen-