Hi,
here is a pull request for the topic at hand, with docs and test:
https://github.com/geoserver/geoserver/pull/674
The pull grew larger than I anticipated because looking around I've found
that the scale
denominator was computed in different ways in different places, and
sometimes it was
different than the one computed by streaming renderer.
I've thus centralized the scale computation in WMSMapContent and made sure
the
code there matches what streaming renderer does. As a result a couple of
tests
had to be modified.
Cheers
Andrea
On Mon, Aug 4, 2014 at 1:01 PM, Andrea Aime <[email protected]>
wrote:
> Hi,
> I would like to propose that we add a new parameter to GetMap (and
> GetFeatureInfo)
> requests to control how we compute the scale denominator.
>
> The current code instructs the renderer to use the OGC compliant scale
> computation,
> e.g.:
>
> rendererParams.put(StreamingRenderer.SCALE_COMPUTATION_METHOD_KEY,
> StreamingRenderer.SCALE_OGC);
>
> This is done for compatibility, but it's well known that the scale
> computation
> against geographic data is way off the true scale, the SLD spec basically
> requires to use equations that assume the earth is a cylinder.
>
> When doing GetMap to be displayed on a computer that is not an issue, as
> people
> do not measure the map on a display by hand, but normally have a distance
> tool
> available instead.
>
> However, when we are using GetMap to integrate the result in a printed
> map, then
> we have a problem: people _do_ measure the printed map by hand, and need an
> accurate result.
>
> Indeed mapfish-print does use accurate equations (so that the printed map
> is actually
> measurable by hand), not the OGC ones, and this is causing
> issues when printing, like for example layers disappearing due to scale
> dependencies
> triggering when they were not meant to.
>
> So, for the sake of printing (and PDF output too), I'm proposing to add a
> new vendor
> parameter to GetMap to control how we compute the scale:
> &scaleMethod=ogc/accurate (default to ogc of course)
>
> The method would not be part of format_options, as it's not really format
> dependent,
> but it would be a new top level vendor parameter.
> Since it's a new features, I'd commit it on master after the feature
> freeze ends
>
> Opinions?
>
> Cheers
> Andrea
>
>
> --
> ==
> GeoServer Professional Services from the experts! Visit
> http://goo.gl/NWWaa2 for more information.
> ==
>
> Ing. Andrea Aime
> @geowolf
> Technical Lead
>
> GeoSolutions S.A.S.
> Via Poggio alle Viti 1187
> 55054 Massarosa (LU)
> Italy
> phone: +39 0584 962313
> fax: +39 0584 1660272
> mob: +39 339 8844549
>
> http://www.geo-solutions.it
> http://twitter.com/geosolutions_it
>
> -------------------------------------------------------
>
--
==
GeoServer Professional Services from the experts! Visit
http://goo.gl/NWWaa2 for more information.
==
Ing. Andrea Aime
@geowolf
Technical Lead
GeoSolutions S.A.S.
Via Poggio alle Viti 1187
55054 Massarosa (LU)
Italy
phone: +39 0584 962313
fax: +39 0584 1660272
mob: +39 339 8844549
http://www.geo-solutions.it
http://twitter.com/geosolutions_it
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