<div>I'm currently supporting a system that has some performance issues. It seems like the overviewed rasters have been replaced by some non over-viewed rasters, so I want to try and add some overviews to improve performance. However, disk space is at a premium, so I am trying to do it in a space efficient way as well.</div>
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<div>The TIFs at the moment average around 5-7Mb each. I currently have a total of 100Gb of files. I'm using them in a system powered by MapServer, and whilst they all display, the performance is poor.</div>
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<div>A GDALINFO report gives the following kind of information - </div>
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<div>>gdalinfo TQ00.TIF<br>Driver: GTiff/GeoTIFF<br>Size is 4000, 4000<br>Coordinate System is `'<br>Metadata:<br> TIFFTAG_XRESOLUTION=254<br> TIFFTAG_YRESOLUTION=254<br> TIFFTAG_RESOLUTIONUNIT=2 (pixels/inch)<br>
Corner Coordinates:<br>Upper Left ( 0.0, 0.0)<br>Lower Left ( 0.0, 4000.0)<br>Upper Right ( 4000.0, 0.0)<br>Lower Right ( 4000.0, 4000.0)<br>Center ( 2000.0, 2000.0)<br>Band 1 Block=4000x8 Type=Byte, ColorInterp=Red<br>
Band 2 Block=4000x8 Type=Byte, ColorInterp=Green<br>Band 3 Block=4000x8 Type=Byte, ColorInterp=Blue<br>Band 4 Block=4000x8 Type=Byte, ColorInterp=Alpha<br> </div>
<div>If I try and add an overview to these files (file copied to maintain the original), I get screens of error messages</div>
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<div>gdaladdo TQ00ov.TIF 2 4 8 16<br>0.ERROR 1: MissingRequired:TQ00ov.TIF: TIFF directory is missing required "Colormap" field<br>ERROR 1: MissingRequired:TQ00ov.TIF: TIFF directory is missing required "Colormap" field<br>
ERROR 1: MissingRequired:TQ00ov.TIF: TIFF directory is missing required "Colormap" field<br>ERROR 1: MissingRequired:TQ00ov.TIF: TIFF directory is missing required "Colormap" field<br>ERROR 1: MissingRequired:TQ00ov.TIF: TIFF directory is missing required "Colormap" field<br>
ERROR 1: MissingRequired:TQ00ov.TIF: TIFF directory is missing required "Colormap" field<br>ERROR 1: MissingRequired:TQ00ov.TIF: TIFF directory is missing required "Colormap" field<br>etc..</div>
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<div>If I try and translate the original first, I get the following error messages</div>
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<div>gdal_translate -ot Byte -of GTiff -co "TILED=YES" TQ00tif.TIF TQ00tiled.TIF<br>Input file size is 4000, 4000<br>0...10...20...30...ERROR 1: TIFFAppendToStrip:TQ00tiled.TIF: Write error at scanline 3072<br>
ERROR 1: TIFFAppendToStrip:TQ00tiled.TIF: Write error at scanline 3072<br>ERROR 1: TIFFAppendToStrip:TQ00tiled.TIF: Write error at scanline 3328<br>ERROR 1: TIFFAppendToStrip:TQ00tiled.TIF: Write error at scanline 3328<br>
ERROR 1: TIFFAppendToStrip:TQ00tiled.TIF: Write error at scanline 3584<br>ERROR 1: TIFFAppendToStrip:TQ00tiled.TIF: Write error at scanline 3584<br>ERROR 1: TIFFAppendToStrip:TQ00tiled.TIF: Write error at scanline 3840<br>
ERROR 1: TIFFAppendToStrip:TQ00tiled.TIF: Write error at scanline 3840<br>ERROR 1: TIFFAppendToStrip:TQ00tiled.TIF: Write error at scanline 0<br>ERROR 1: TIFFAppendToStrip:TQ00tiled.TIF: Write error at scanline 0<br>ERROR 1: TIFFAppendToStrip:TQ00tiled.TIF: Write error at scanline 256<br>
ERROR 1: TIFFAppendToStrip:TQ00tiled.TIF: Write error at scanline 256<br>ERROR 1: TIFFAppendToStrip:TQ00tiled.TIF: Write error at scanline 512<br>ERROR 1: TIFFAppendToStrip:TQ00tiled.TIF: Write error at scanline 512<br>ERROR 1: TIFFAppendToStrip:TQ00tiled.TIF: Write error at scanline 768<br>
etc...</div>
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<div>I've got this to work on one or two of the files, but the resultant TIF is now averaging 90Mb, rather than 7Mb, and thats without adding overviews on top of that.</div>
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<div>An example tile and worldfile can be found here</div>
<div><a onclick="return top.js.OpenExtLink(window,event,this)" href="http://sites.google.com/a/vanbooth.com/transfer/Home" target="_blank">http://sites.google.com/a/vanbooth.com/transfer/Home</a></div>
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<div>I'm currently using GDAL <a onclick="return top.js.OpenExtLink(window,event,this)" href="http://1.2.0.0/" target="_blank">1.2.0.0</a> (released 2004/03/01) on AIX.</div>
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<div>Has anybody got any idea of how I can convert these rasters to something useable and performant?</div>
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<div>MTIA</div>
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<div>Rob</div><br>