[gdal-dev] libkml GroundOverlay support

[Even Rouault]

Le lundi 05 mars 2012 16:01:22, Clarke, Trevor a écrit :
> I am in need of support for GroundOverlay loading from KML and I've been
> prototyping some ideas. The biggest issue is that GroundOverlays are
> conceptually raster data in a primarily vector format so it's unclear
> how OGR/GDAL should handle this. It's useful to have relational
> information and bounding rectangle information coming back from OGR but
> OGR shouldn't load the raster data, that's obviously a GDAL job.
> 
> For background, here's now GroundOverlays are specified. A GroundOverlay
> element has to have a LatLonBox to specify the bounding rectangle for
> the imagery and it also needs to have a URL specifying the source of the
> imagery. This can be a web url, a file url or a relative path (if it's
> in a KMZ). In addition, descriptive metadata and a DrawOrder can be
> specified. Defined behavior when an image URL isn't specified or can't
> be loaded is to draw a rectangle with the specified (or default) color
> and style information.
> 
> I propose the following behavior. In OGR, the GroundOverlay is added as
> a polygon feature specifying the bounding box and style/draw information
> for the "can't load" display mode. Draw order, and URL are attached as
> fields as well as a field indicating this is a GroundOverlay and not a
> Placemark. This is enough to load and work with the bounds, etc. and the
> URL can be passed to GDAL for raster loading (via /vsicurl/ if
> necessary).
> 
> This will not allow a user to pass a KML directly to GDAL and get access
> to the embedded images.
> 
> Thoughts?

There's a GDAL KMLSuperOverlay driver that is currently write-only. Shouldn't 
read mode be added to it ?

> 
> ------------------
> Trevor R.H. Clarke
> Ball Aerospace & Technologies Corp
> Opticks, Free Your Imagery (http://opticks.org)
> GPG key available on random.sks.keyserver.penguin.de
> 
> 
> 
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