Hi,
I haven't been playing with WCS for a while so I may be a bit lost but I hope I
can give some help.
First, what you experience is probably wrong and service should send data by
using the gridOffsets which are advertised in the describeCoverage response
independently of the boundingbox used in the request.
However, if I were you I would just add &GridOffsets= to the query and tell
explicitly what resolution I want to get. Actually myself I prefer to use WCS
1.0.0 because for me the BBOX= and RESX= RESY= parameters are somehow easier to
remember and with raster maps and aerial images they offer all the
functionality I need.
It would be fine if you can reproduce the error with some of the demo coverages
listed by
http://localhost:8080/geoserver/ows?service=wcs&version=1.1.1&request=GetCapabilities
and file a Jira issue.
-Jukka Rahkonen-
________________________________
Timothy Astle wrote:
I'm not sure what's going on, so I'm going to describe what I'm observing.
If I make the following WCS request (using the provided Img_Sample data)
/geoserver/ows?service=wcs&version=1.1.0&request=GetCoverage&identifier=Img_Sample&format=image/tiff&boundingbox=20.7052,-130.85168,54.1141,-62.0054,urn:ogc:def:crs:EPSG::4326&RangeSubset=contents
I get roughly, an 8 MB response with the image resolution being 983x2026 pixels.
If I make the following request (narrowing the bounding box):
/geoserver/ows?service=wcs&version=1.1.0&request=GetCoverage&identifier=Img_Sample&format=image/tiff&boundingbox=54,-63,54.1141,-62.0054,urn:ogc:def:crs:EPSG::4326&RangeSubset=contents
I get roughly, a 33 MB response with the image resolution being 983x8569 pixels.
And so forth. The smaller the bounding box, the exceedingly big the response
(until I start seeing clipping errors). Also, the width stays constant at 983
pixels. I've tried this with other data, and reproduced similar behaviour. If
I do the same boundingbox extent reduction with MapServer, I get smaller
responses, with a lower resolution (image size). Is GeoServer somehow
upsampling the data, ignoring the grid definition of the coverage described in
the Coverage Description response?
Using GDAL as a client, I'm getting ridiculous amounts of data for a 2x2
request. (See what Frank was doing here:
http://jira.codehaus.org/browse/GEOS-1717)
I first noticed this with the following GeoServer instance. Here's the first
request made by GDAL. It is a 2x2 request, and it's returning 11 GB(!!) of
data.
(FYI: Replace DOT with . in the domain to try it out. I don't want any bots
triggering this while crawling this post.)
http://geodataDOTnationaalgeoregisterDOTnl/ahn2/wcs?SERVICE=WCS&VERSION=1.1.1&REQUEST=GetCoverage&IDENTIFIER=ahn2_5m&FORMAT=image%2Ftiff&BOUNDINGBOX=19242.5,506242.5,19247.5,506247.5,urn:ogc:def:crs:EPSG::28992&RangeSubset=contents
Am I forgetting something, because something doesn't seem right to me.
Cheers,
Tim Astle
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