[mapserver-users] Ed's Rules for the Best Raster Performance

[Steve Lime]

Interesting idea. This could take the form of a tile index with a couple of additonal columns, minscale and maxscale. Tiles would
be grouped together by using common with those values. You could do interesting things like have high resolution data in 
some areas with other areas covered with lower resolution data over a broader range of scales. The whole layer could have it's 
own floor/ceiling but tiles would be handled individually.

I wouldn't handle this as a new layer type, but rather by introducing parameters to indicate which columns to use, kinda like
TILEITEM. Your pyramids would be defined in the tile index...

I think the gdal tools would already support this nicely since they add to an index if it already exists so you could run those tools
over mutliple datasets. Vector layers could also be handled this way, no reason you couldn't have 1 tile per scale range.

Steve

>>> On 9/15/2008 at 2:18 PM, in message <48CEB4F5.9020809 at geoanalytic.com>, Brent
Fraser <bfraser at geoanalytic.com> wrote:

> Jeff McKenna wrote:
>> my quick comments:
>> 
>> - adding overviews with GDAL's 'gdaladdo' utility is very important
> 
> In some cases.  It depends on your data.  As Ed once posted, it may be a 
> good idea to switch to external overviews and merge some of the files to 
> limit the number of file-opens Mapserver must do when the view is zoomed way 
> out.
> 
>> - I find your use of the word "pyramid" confusing (this seems to be a 
>> word that Arc* users are familiar with but has no real meaning in the 
>> MapServer world...I guess I've been on the "good" side for too long ha)
>> 
> Not being an Arc* user I can't comment on it's origins.  "Overview" is a 
> good alternative, but it doesn't seem to convey the same "multi-levelness" as 
> pyramids.  For example to be able to display the Global Landsat Mosaic, I 
> created seven levels of a pyramid (each an external overview of the 
> higher-resolution below it).  
> 
> Hmmm, may be the plural of overview is pyramid... :)
> 
> Hey Steve L., maybe we should have a "PYRAMID" Layer type, to replace a set 
> of scale-sensitive TILEINDEX Layers (this would help my 
> every-layer-is-exposed-in-WMS problem too: 
> http://trac.osgeo.org/mapserver/ticket/300).
> 
> Brent
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