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WCS :: OGC Bonn 2005-nov-09
Some GALEON Results for WCS
OGC, Bonn, 2005-nov-09
Peter Baumann
International University Bremen,rasdaman GmbH
email: [email protected]
2WCS :: OGC Bonn 2005-nov-09
IUB @ GALEON
Implementation of a WCS server based on a raster DBMS• XML / SOAP
Intermediate results• Specification of GetCoverage coverage data result
• List of editorial change requests
• Issues
Decision WCS.RWG: incorporate in WCS 1.1
3WCS :: OGC Bonn 2005-nov-09
GetCoverage Evaluation Model
select source coverage
perform spatial subsetting
perform temporal subsetting
perform range subsetting (*)
perform spatial scaling into result bbox (*)
perform reprojection into target CRS (+)
perform data format encoding
transmit resulting byte string to target location
(*) including interpolation as specified
(+) may involve implicit range interpolation and, hence, accuracy loss, depending on the format chosen
discussion
appreciated
4WCS :: OGC Bonn 2005-nov-09
Issues (1)
Q: If I have a coverage with temporal domain { [0:3], [7:10]}, and I select T=5 – what is the result? What if T=20?A: in both cases, an exception has to be reported.
Q: Is there any scaling / interpolation along the time axis?A: Currently not foreseen.
Proposal: make "grid" (ie, cell/pixel/voxel/…) coordinates visible to clients
geo2cell-coord
cell-indexed coverage
5WCS :: OGC Bonn 2005-nov-09
Issues (2)
Q: the correspondence of BoundingBox and SpatialSubset in a GetCoverage request is not clear.
Q: When is dimension of result coverage reduced wrt. original coverage?A: Currently not foreseen, however considered useful.
x
yt
6WCS :: OGC Bonn 2005-nov-09
Side effect of coverage result spec:good basis for value-added services
Under work: WCPS = Web Coverage Processing Service = coverage retrieval & processing• expression language
• Declarative = describe what you want, not how to compute
based on model & functionality of WCS
WCPS
7WCS :: OGC Bonn 2005-nov-09
WCPS language expressions independent from encoding• Example: tiff( C.red + C.nir )
KVP encoding: WCPS language + entities where needed• Example:
http://myhost/myservice ? SERVICE=WCPS & VERSION=0.0.1 & REQUEST=tiff(C.red%20+%20C.nir) & EXCEPTIONS=application/vnd.ogc.se_xml
XML encoding: XML Schema• Example:
<formatEncoding format="tiff"><binaryPlus>
<structSelection component=„red“ coverage=„C“/><structSelection component=„nir“ coverage=„C“/>
</binaryPlus></formatEncoding>
WCPS Concepts
8WCS :: OGC Bonn 2005-nov-09
DLR Value-Added Satellite Image Service
9WCS :: OGC Bonn 2005-nov-09
Web Map Service: Example
http://myServer/wmsServlet?VERSION=1.1.0 &SERVICE=WMS & REQUEST=GetMap &SRS=EPSG:31464 &BBOX=4636000.0,5717000.0,4687000.0,5768000.0 &LAYERS=ortho,DEM,waterareas,waterlines &STYLES=standard,custom,AdV,AdV &WIDTH=246 & HEIGHT=300 &FORMAT=image/jpeg &EXCEPTIONS=application/vnd.ogc.se_inimage & …
SELECT jpeg( scale(img0[...],[1:246,1:300]) * { 1c, 1c, 1c}
overlay ((scale(img1[...],[1:246,1:300])<71.0))* { 51c, 153c, 255c} overlay bit(scale(img7[...],[1:246,1:300]), 4) * {191c, 255c, 255c} overlay bit(scale(img8[...],[1:246,1:300]), 1) * { 0c, 255c, 255c} ) FROM ...
SELECT jpeg( scale(img0[...],[1:246,1:300]) * { 1c, 1c, 1c}
overlay ((scale(img1[...],[1:246,1:300])<71.0))* { 51c, 153c, 255c} overlay bit(scale(img7[...],[1:246,1:300]), 4) * {191c, 255c, 255c} overlay bit(scale(img8[...],[1:246,1:300]), 1) * { 0c, 255c, 255c} ) FROM ...
10WCS :: OGC Bonn 2005-nov-09
Summary
GetCoverage result spec
Database-backed WCS under way• Operational next 2-3 weeks
WCPS = WCS + coverage processing expression language• demo implementation
started (student thesis work)
Thank you for your attention!