Jan Hartmann wrote:
Is this a bug? Shouldn't MapServer use the gdaladdo overviews at the
appropriate scales?
Rich / Jan,
No, generally I treat raster query as an "exact" operation done
against the full resolution data. The overviews are only used
to satisfy downsampled RasterIO requests such as drawing a reduced
resolution map.
Best regards,
On 08/17/10 16:09, Richard Greenwood wrote:
I am working with a single band raster of 10mX10m cells. I have added
overlays with gdaladdo and it displays nicely.
When I query the layer I am using MODE=nquery, not MODE=query. The
reason that I am using nquery is unrelated to the raster layer, but
I'm pretty much restricted to using that mode. At large scales this
returns at least 2 cells, which I can average easily with JavaScript
in the browser. However at small scales I'm getting 10s of 1000s of
cells which are really slowing things down. It does not appear that
query or nquery mode is using the overlays. Anyone disagree with that
assumption?
So the only solution that I've come up with thus far is to resample
the raster to larger cell sizes and use the min/max scale denominator
to select a layer with cell size appropriate to the scale. Anybody
have other ideas?
Thanks,
Rich
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