On Wed, Feb 22, 2012 at 1:36 PM, Ollie Newman
<oliver.new...@baesystems.com>wrote:
> Apologies if this is not strictly a GeoServer question, it may be a WFS
> specification question..
>
> If I have a data layer of polygons in one CRS e.g epsg:4326 and I make a
> WFS
> request against it with an intersects filter using a linestring encoded in
> a
> different CRS e.g epsg:900913 what is the behaviour of the intersection if
> the line is long and curvature of the earth comes into play?
>
> I believe that linestrings are linearly interpolated but are the 900913
> coordinates converted to 4326 and then linearly interpolated in the 4326
> CRS, or is the linestring linearly interpolated in it's supplied CRS
> (900913) and then tested against the 4326 data as the two would potentially
> give different answers.
>
>
GeoServer WFS can filter against geometries in other projections, you just
need
to specify the native crs of the geometry in the filter.
However, as you suspect, the reprojection we do is dumb, it's point by
point,
so it does not take into account the fact that some lines should becomes
curves
when reprojected.
Given that the only type of linear geometry that we can handle is made of
straight
segment, to get more accurate reprojection we'd need code that densifies
long
straight lines, the finer the more deformation a projections applies in
that area,
and then reproject that version.
Something like that would be needed for rendering reprojected geometries
with
long segments in WMS too.
Hopefully someone will show up that sponsors this feature.
Cheers
Andrea
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