Improve WMS Server Performance

[Frank Warmerdam]

On 2/7/06, Kyle Mulka <mulka at umich.edu> wrote:
> That seemed to work pretty well after I first converted my jpegs to
> geotiffs using gdal_translate. It didn't work at all (took hours) trying
> to go directly from jpeg to tiled tiff.

Kyle,

I can see why you were originally having trouble.  Large
JPEGs are a particularly inefficient format for large raster data
that you will want subsections of.

I'm not sure why a direct translation from JPEG was so bad.
Likely some sort of "cache thrashing" problem that would cause
large amounts of data to be re-read for each tile being rewritten.
You can set the GDAL_CACHEMAX value to allow GDAL to use
a cache larger than it's default 10MB.

> Now, I'm having a problem at the borders of both the original tiles and
> the rended tiles from mapsever:
> http://maps.kylemulka.com/spot/
>
> You should notice that the initial map you see when the page first loads
> looks fine. Then, zoom out and you will see two white lines. Any way to
> fix that?

I have no idea why that is.  Some sort of subtle resampling
error I suppose, or perhaps wrong bounds on your rasters.
There isn't really anything I can do about it unless you can
replicate it in a minimal situation you can submit in a bug report.

Best regards,
--
---------------------------------------+--------------------------------------
I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | Geospatial Programmer for Rent