Raster image doesn't show

[d c]

Ed,

This is the extent of my map:

EXTENT -3174450 -2816050 2867175 2406325
UNITS METERS

I'm trying to display a point element on a geotiff raster file, as follows
(Note the decimal degree format):

LAYER
    TYPE POINT
    STATUS DEFAULT
      FEATURE
        POINTS
            56.5333333 -71.5  #  <------- DD
        END
        TEXT "HELLO WORLD"
    END
    CLASS
        COLOR 255 0 0
        SYMBOL 'cross'
        LABEL
            TYPE bitmap
        END
    END
    TOLERANCE 5
END

The label, according to the coordinates given, sometimes appears, sometimes
does not and most often
on the same (erroneous) spot.

I tried to change the EXTENT (and UNITS) to decimal degrees according to the
output of gdalinfo which outputs corner coordinates both in meters and
decimal degrees. I thought I could this way make Mapserver understand I was
specifying the input in decimal degrees so it should output correctly the
point I want to draw. The scalebar also revealed seriously confused.

I did not mention that the map is of Antarctica. This apparently complicates
the matter since the EXTENT values are different than on most maps.

I'm new to this so I haven't got much knowledge about projections. The
following two I have used successfully in displaying the map (but not the
point):

PROJECTION
 "proj=stere"
 "ellps=WGS84"
 "datum=WGS84"
 "lon_0=0"
 "lat_0=-90"
 "lat_ts=-71"
 "units=m"
END

PROJECTION
  "init=esri:102021"
END

Thanks for your help,

Dan


2006/5/5, Ed McNierney <ed at topozone.com>:
>
> D C -
>
> The UNITS and EXTENT in your mapfile need to correspond to the units used
> in the projection of your data.  If they don't, then you're looking to
> reproject the data and there's some extra work you need to do.
>
> gdalinfo will tell you the units and extent in the data source's native
> projection.  Changing those values in the mapfile won't change the input
> data, and you're simply requesting an output image that doesn't correspond
> to any part of your input data, so you (correctly) get nothing displayed.
>
> What is it you're trying to do?  Are you trying to display the image in a
> different projection than the raster source image is using?  If so, what
> projection does the raster use and what output projection do you want?
>
>     - Ed
>
> Ed McNierney
> President and Chief Mapmaker
> TopoZone.com / Maps a la carte, Inc.
> 73 Princeton Street, Suite 305
> North Chelmsford, MA  01863
> ed at topozone.com
> (978) 251-4242
>
>  ------------------------------
> *From:* UMN MapServer Users List [mailto:MAPSERVER-USERS at LISTS.UMN.EDU] *On
> Behalf Of *d c
> *Sent:* Friday, May 05, 2006 5:54 AM
> *To:* MAPSERVER-USERS at LISTS.UMN.EDU
> *Subject:* [UMN_MAPSERVER-USERS] Raster image doesn't show
>
> Hello,
>
> I just changed the EXTENT of my mapfile which was in METERS to DD.
> I just wrote down the corresponding decimals which were given by gdalinfo.
>
> BEFORE
> --------------
> UNITS METERS
> EXTENT -3174450 -3225675 2867175 2815950
>
>
> AFTER
> -----------
>
> UNITS DD
> EXTENT  -131.5 -56.5 134 -52.3
>
> nb: the map is a raster im. of antarctica
>
> The PROBLEM now is that THE MAP DOESN'T SHOW.
> I don't get an error or anything, the map just doesn't show.
>
> Any suggestions?
>
> Thanks in advance.
>
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