rows per strip in TIFF rasterfiles

[Frank Warmerdam]

On 9/30/05, Manfred Zerndl <manfred.zerndl at bvv.bayern.de> wrote:
>
> With the TIFF-dataformat you can set "rows per strip" (rps) to a
> user-defined value.
> (1) What is better, setting "rps" to a small value, maybe 1 or a big
> value ?  Or is irrelevant for the performance?
>
> When I have a TIFF-File with  20 000 x 20 000 Pixels, I think mapserver
> should be faster
> when the tiff-files have a small rps-value.

Manfred,

If you set the "rows per strip" to 1, then MapServer can extract
overviews reasonably efficiently by only pulling out the scanlines
it needs.   So, for wide files that is my suggestion.

> (2) Do I need special generated TIFF files, so that mapserver
> is able to load a small section from a big TIFF-File?

A better approach than stripping is to use tiling within the TIFF file.
Commands like the following will convert your GeoTIFF file to tiled
organization and build overviews.  This is pretty much optimal for
fast mapserver rendering at different resolutions.

gdal_translate -co TILED=YES in.tif out.tif
gdaladdo out.tif 2 4 8 16 32 64

Best regards,
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
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