Hi Radim,
Here is a working mapfile reprojecting a PostGIS layer:
https://github.com/mapserver/mapserver/wiki/Reproject-PostGIS-Layer
You ask good questions, that could likely just be tested by checking the
postgres logs and executing the raw commands from those logs at the psql
commandline and comparing.
As you go down this path, please do add to that new wiki page with your
own notes :)
-jeff
--
Jeff McKenna
MapServer Consulting and Training Services
https://gatewaygeomatics.com/
On 2019-07-18 8:04 AM, Radim Blazek wrote:
Hi Jeff,
thanks, yes I have read that.
But I also read that "using srid= is optional but improves
performance" so there was a little chance that re-projection could be
done anyway if a different SRID is found on geometry.
If there is no further transformation, what difference "using srid="
does? What happens if SRID is not set on column and there are mixed
geoms' SRIDs.
I mean, where is CRS transformation done if request CRS != layer CRS
!= column CRS? I would expect calling directly PostGIS
ST_Transform(geom, request_srid), which would by pass
LAYER.PROJECTION.
Radim
On Thu, Jul 18, 2019 at 12:31 PM Jeff McKenna
<jmcke...@gatewaygeomatics.com> wrote:
Hi Radim,
Give the Projection document a good read specifically the "Important
Notes" section which I believe answers your questions:
https://mapserver.org/mapfile/projection.html#important-notes
There are no specific driver rules; for something like a PostGIS
connection you should be able to follow the "Important Notes" above.
MapServer will assume that you have configured the driver properly (in
the case of PostGIS, setting the SRID as well, since PostGIS requires
that parameter to do a projection)
-jeff
--
Jeff McKenna
MapServer Consulting and Training Services
https://gatewaygeomatics.com/
On 2019-07-18 5:59 AM, Radim Blazek wrote:
Hi,
can you please explain how does re-projection of PostGIS layers work?
If there is a POSTGIS layer with DATA without "using srid=" but
PostGIS column has SRID defined, there is constraint for that SRID on
the column and geometries have SRID set, is it necessary to define
PROJECTION for that layer if SRID of the column is different from that
of mapfile?
For example, geometry column has SRID=4326, geometries have SRID set, mapfile:
NAME test
PROJECTION
"init=epsg:3857"
END
LAYER test
CONNECTIONTYPE postgis
DATA "geo FROM test"
END
END
if a request comes to render a map in 3857, will be geometries
re-projected correctly from 4326 to 3857?
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