[mapserver-users] Rotating a map

[Dave Howlett]

Yes using Proj can help you out there. It may depend on what type of projection you intend to use. I'm using a
Lambert Conformal Conic projection and can turn the map by changing what is specified as my central meridian.

This is my normal output projection for Canada:

PROJECTION
     "proj=lcc"
     "ellps=GRS80"
     "lat_0=49"
     "lon_0=-95"
     "lat_1=49"
     "lat_2=77"
END

If I change lon_0 to -5 then the image will be rotated by 90 degrees clockwise, and St. John's ends up becoming the
Miami of Canada.

Hope this helps!

Dave

Tyler Mitchell wrote:

> Frank Warmerdam wrote:
>
> >As it happens GDAL will read these in and use these rotational
> coefficients
> >when going through the resampling process, so the image gets rotated back
> >to north-up.  You can accomplish the same thing by putting rotational
> >coefficients in a world file.  The above file would have a world file that
> >looks like this:
>
> Will this only apply to an image layer as it is loaded?
> What about changing the whole map before it is display in the browser - any
> ideas?
>
>
>                     Frank Warmerdam
>                     <warmerdam at pobox.com>               To:     Tyler Mitchell <TMitchell at lignum.com>
>                     Sent by:                            cc:     UMN MapServer <mapserver-users at lists.gis.umn.edu>
>                     owner-mapserver-users at lists.g       Fax to:
>                     is.umn.edu                          Subject:     Re: [mapserver-users] Rotating a map
>
>
>                     01/10/2002 05:49 PM
>                     Please respond to warmerdam
>
>
>
> Tyler Mitchell wrote:
>
> > Hi guys,  what would you do to rotate the orientation of your map?  Is
> > using Proj realistic or not?
> > I saw some emails back in July about this question - has anyone gone
> > anywhere with this idea?
>
> Tyler,
>
> I have successfully used the resampling code in MapServer to do some
> rotation of an ortho image.  In my particular test the georeferencing
> information in a GeoTIFF file included rotational coefficients as shown
> here:
>
> warmerda at gdal[483]% listgeo small.tif
> Geotiff_Information:
>     Version: 1
>     Key_Revision: 1.0
>     Tagged_Information:
>        ModelTransformationTag (4,4):
>           0.999978707      -0.0065257527    0                467086.89
>           -0.0065257527    -0.999978707     0                5365917.48
>           0                0                0                0
>           0                0                0                1
>        End_Of_Tags.
>     Keyed_Information:
>        End_Of_Keys.
>     End_Of_Geotiff.
>
> As it happens GDAL will read these in and use these rotational coefficients
> when going through the resampling process, so the image gets rotated back
> to north-up.  You can accomplish the same thing by putting rotational
> coefficients in a world file.  The above file would have a world file that
> looks like this:
>
> warmerda at gdal[487]% more small.tfw
>              0.9999787070
>             -0.0065257531
>             -0.0065257527
>             -0.9999787072
>         467087.3871740954
>        5365916.9739565337
>
> Please feel free to contact me if you have problems settings this up and
> doing it.  It is a rather esoteric use of the mapserver resampling logic.
>
> PS. I have placed this text in the Wiki as:
>
>    http://mapserver.gis.umn.edu/cgi-bin/wiki.pl?RotatingImages
>
> 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    | Geospatial Programmer for Rent