mapserv and ogr2ogr reprojection (Google Earth)

David William Bitner bitner at GYTTJA.ORG
Mon Sep 25 09:41:33 PDT 2006


That functionality would also offer instant "zip & ship" capabilities to
MapServer which is something that is becoming a requirement for many data
providers to be able to provide custom clipped data files over the web.

On 9/25/06, Frank Warmerdam <warmerdam at pobox.com> wrote:
>
> Eijnden, Bart van den (AGI) wrote:
> > Hi list,
> >
> > first of all, maybe this would be better addressed at the gdal-dev list
> as
> > well.
> >
> > Using Jan Hartman's PROJ.4 parameters for EPSG:28992
> > (
> http://postgis.refractions.net/pipermail/postgis-users/2005-November/009894.html
> ),
> > we successfully got Dutch national grid data to match the aerial
> > photography of Google Earth.
> >
> > We used Mapserver WFS and ogr2ogr (GML input, KML output) to transform
> the
> > data.
> >
> > If we transform using ogr2ogr and provide -s_srs with the exact same
> PROJ.4
> > string and t_srs of EPSG:4326, the overlay is not correct.
> >
> > Any ideas what could be causing this? All testing was done using FWTools
> > 1.0.5 on Windows XP.
>
> Bart,
>
> It is not immediately clear to me why this would not work properly.  I
> did check the PROJ.4 coordinate system in question, and it appears to
> go through OGR's internal SRS conversions without any damage.
>
> If you could submit a bug report against OGR with all the details I will
> dig into it.  In particular what I would like to see is a point
> transformed
> through ogr2ogr producing a different output value than the same point
> transformed using cs2cs.   I gather your central premise is that with
> cs2cs you got the expected results, but you didn't see the same results
> with
> ogr2ogr, right?
>
> > Another question:
> >
> > -how hard would it be to have the same OUTPUTFORMAT mechanism for vector
> > (Mapserver WFS/OGR), so that output formats of OGR could be outputted by
> > Mapserver WFS?
>
> It would be a fairly substantial effort I think.  I gather we would need
> something roughly analygous to mapgml.c that can write via an OGR driver,
> and then various machinery connecting up format selection in the wfs
> output.
> Perhaps a 2-3 week development effort.
>
> I think we would also need a mechanism to identify files to "bundle up"
> in a zip or something similar for multi-file formats such as shape, or
> mapinfo.
>
> But I can see that this would be an interesting capability.
>
> Best regards,
> --
>
> ---------------------------------------+--------------------------------------
> I set the clouds in motion - turn up   | Frank Warmerdam,
> warmerdam at pobox.com
> light and sound - activate the windows | http://pobox.com/~warmerdam
> and watch the world go round - Rush    | President OSGeo, http://osgeo.org
>



-- 
************************************
David William Bitner
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