I love it! I had some half-baked convoluted list-of-tileindexes idea; this is much better.
We may have to allow PROJECTION=AUTO for the tiles (in the case where
the tiles are in UTM several zones), and allow the tile index to be in a
different SRS (e.g geographic) than the tiles (I can't recall if this already
implemented; I know it caused me a problem some years ago).
A elegant enhancement with great potential...
Brent
Steve Lime wrote:
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 <[EMAIL PROTECTED]>, Brent
Fraser <[EMAIL PROTECTED]> 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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