[mapserver-users] Spherical Mercator Projection Problem

[Jean-François Gigand]

Hi,

Indeed.

Also note that EPSG:900913 is the same as EPSG:3785 and EPSG:3857.
These three are the Spherical Mercator projection, which is the right
one to use for overlays on Google Maps.


Jean-François Gigand




2011/2/24 Fawcett, David (MPCA) <David.Fawcett at state.mn.us>:
> Sergey,
>
>
>
> If your data is in epsg:4326 and you want to publish the data as epsg:3785,
> you will need to projection blocks to your layers.
>
>
>
> Something like:
>
>
>
>   PROJECTION
>
>             "init=epsg:4326"
>
>   END
>
> The Projection block in the MAP section defines your output projection.
> Because your data is not in the same projection, you will need to define a
> projection block in each layer section.  Those projection blocks define the
> ‘input’ projection.  They tell MapServer what projection the data exists
> in.  This allows MapServer (with proj4 support) to re-project your data to
> the output projection.
>
>
>
> David.
>
>
>
>
>
> From: mapserver-users-bounces at lists.osgeo.org
> [mailto:mapserver-users-bounces at lists.osgeo.org] On Behalf Of Sergey Kraev
> Sent: Wednesday, February 23, 2011 5:01 AM
> To: mapserver-users at lists.osgeo.org
> Subject: [mapserver-users] Spherical Mercator Projection Problem
>
>
>
> Hi,
>
>
>
> I’m running MS4W v3.0 (including MapServer 5.6.5) on Windows.
>
>
>
> My data source are PostGIS multipolygon countries’ borders.
>
>
>
> I have successfully got MapServer to render the world map in WGS84
> projection using these settings:
>
>
>
> Request:
>
>
>
> http://127.0.0.1:8080/cgi-bin/mapserv.exe?map=world.map&mode=map&mapsize=256+256&mapext=-180+-90+180+90
>
>
>
> world.map:
>
>
>
> MAP
>
> EXTENT                   -180 -90 180 90
>
>   #EXTENT         -20037508 -20037508 20037508 20037508
>
>   SIZE           256 256
>
>   IMAGECOLOR     153 179 204
>
>   FONTSET        "c:\MS4W\fonts\fonts.list"
>
>   RESOLUTION        96
>
>   MAXSIZE        5000
>
>
>
>   PROJECTION
>
>             "init=epsg:4326"
>
>             #"init=epsg:3785"
>
>   END
>
> …
>
> <layers don’t have PROJECTION sections>
>
>
>
> I would like MapServer to render the same data into a “Web (spherical)
> Mercator” projected map (epsg:3785), but I don't know how to modify my
> request and mapfile in order to get the correct map.
>
>
>
> With the following settings I just receive a picture without any polygons.
>
>
>
> \ms4w\proj\nad\epsg:
>
>
>
>                  …
>
> <3785> +proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0
> +y_0=0 +k=1.0 +units=m +nadgrids=@null +wktext  +no_defs <>
>
> …
>
>
>
> Request (only mapext is different):
>
>
>
> http://127.0.0.1:8080/cgi-bin/mapserv.exe?map=world.map&mode=map&mapsize=256+256&mapext=-20037508+-20037508+20037508+20037508
>
>
>
> world.map (only EXTENT and PROJECTION are different):
>
>
>
> MAP
>
>   #EXTENT                -180 -90 180 90
>
>   EXTENT         -20037508 -20037508 20037508 20037508
>
>   SIZE           256 256
>
>   IMAGECOLOR     153 179 204
>
>   FONTSET        "c:\MS4W\fonts\fonts.list"
>
>   RESOLUTION        96
>
>   MAXSIZE        5000
>
>
>
>   PROJECTION
>
>             #"init=epsg:4326"
>
>             "init=epsg:3785"
>
>   END
>
> …
>
> <layers don’t have PROJECTION sections>
>
>
>
> I’m assuming that -20037508 -20037508 20037508 20037508 is correct extent
> for the whole world map, since Google uses that and they also have Mercator
> projection.
>
>
>
> Thanks for your help.
>
>
>
> Sergey
>
>
>
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>
>