WCS :: OGC Bonn 2005-nov-09

Some GALEON Results for WCS

OGC, Bonn, 2005-nov-09

Peter Baumann

International University Bremen,rasdaman GmbH

email: p.baumann@iu-bremen.de

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!