[Gdal-dev] WCS Client Driver

[Kralidis,Tom [Burlington]]

> -----Original Message-----
> From: Frank Warmerdam [mailto:warmerdam at pobox.com] 
> Sent: 04 October, 2006 2:01 PM
> To: Kralidis,Tom [Burlington]
> Cc: gdal-dev; Bart van den Eijnden (OSGIS)
> Subject: Re: [Gdal-dev] WCS Client Driver
> 
> Kralidis,Tom [Burlington] wrote:
> > Hi,
> > 
> > (jumping up and down -- good news!).
> > 
> > This will undoubtedly increase the usage of WCS servers.
> > 
> > Though I'm not a part of the PSC, I provide the following comments
> > (interleaved): 
> ...
> >> The WCS coverage driver will read a service description file to 
> >> establish the parameters it requires to make GetCoverage 
> calls on a 
> >> WCS server.  If the the service description file lacks 
> >> DescribeCoverage information for the coverage, the driver 
> will invoke 
> >> DescribeCoverage, and fill in the service description file on disk.
> >>
> > 
> > In terms of MapServer, this is a bit different than the other OWS 
> > client approaches (i.e. the code is in MapServer itself for 
> WMS, WFS client).
> > I would be interested in how this functionality will "roll up" to 
> > MapServer and what the relationship is.  Just want to make 
> sure there 
> > are little/no duplications.
> 
> Tom,
> 
> This is indeed quite different from the approach in MapServer 
> for WFS and WMS client support.  Mainly this different is 
> because the client isn't using GDAL from MapServer, so I 
> needed to implement a GDAL-only approach.
> 
> So, in a sense there will be some duplication of mechanisms 
> but I don't see it as easily avoidable.
> 
> >> Specification Features
> >> ----------------------
> >>
> >> Version:
> >>   o The driver will support WCS version 1.0.0.
> >>   o The driver will support WCS version 1.1.0 based on 
> current draft. 
> >> (Phase 2)
> > 
> > I'm pretty sure 1.1.0 implements the owsCommon specification.  It 
> > would be valuable when implementing anything from owsCommon that it 
> > can be reused in some way.  I could see this being leveraged in 
> > MapServer (even as a code copy/paste) for the logic.
> 
> I'm not sure how easy sharing will be (other than as example code).
> 
> BTW, what version(s) of WMS and WFS use owsCommon?  It might 
> make sense at some point to implement WFS and WMS client 
> support in OGR and GDAL respectively, and some leverage of 
> owsCommon might apply at that point.
> 

OGC:WMS does not use it yet, but will (1.4.0?).  OGC:WFS 1.1.0 uses
owsCommon (http://schemas.opengis.net/wfs/1.1.0/wfs.xsd).

> > Frank: you may want to look at what we did for the 
> OWSContext work for 
> > binding to a WCS in a context doc.
> 
> Could you provide a specific pointer for me, and what I 
> should be looking for?
> 

If you're an OGC member, an example is available at:

https://portal.opengeospatial.org/wiki/twiki/bin/view/OWSContextie/Web

Else, here's an XML snippet of what a WCS Coverge binding would look
like:

		<Coverage hidden="0">
			<Server service="OGC:WCS" version="1.0.0"
title="Boston Indexed Geotiff imagery">
				<OnlineResource method="GET"
xlink:type="simple"
xlink:href="http://webservices.ionicsoft.com/ionicwcs/coverage/BOSTONPOO
L"/>
			</Server>
			<Name>MOD_Grid_L2g_2d</Name>
			<Title>MOD_Grid_L2g_2d Coverage Offering</Title>
			<Abstract>MOD_Grid_L2g_2d Coverage Offering,
MOD09GHK data</Abstract>
			<MetadataURL format="text/xml">
				<OnlineResource xlink:type="simple"
xlink:href="http://webservices.ionicsoft.com/ionicwcs/coverage/BOSTONPOO
L/REQUEST/getdir/DIR/metadata/DATA/LPR/BOSTONPOOL/MOD_Grid_L2g_2d.xml"/>
			</MetadataURL>
			<SRS>EPSG:4326</SRS>
			<FormatList>
				<Format current="1">GEOTIFF</Format>
			</FormatList>
			<DimensionList>
				<Dimension name="time"
units="ISO8601">2003-12-01T14:55:00Z/2003-12-03T20:50:00Z</Dimension>
			</DimensionList>
			<ParameterList>
				<Parameter>
					<param:kvp name="band"
value="band1"/>
				</Parameter>
				<Parameter>
					<param:kvp name="interpolation"
value="nearest neighbor"/>
				</Parameter>
			</ParameterList>
		</Coverage>