Image projection question

Thu Jun 14 18:35:18 PDT 2007

G'day Jacob.

The map that is displayed by MapServer shows the polygons some 20 m due 
north of the "correct" location relative to the background raster but 
the mouse coordinates displayed when pointing at the polygons seem 
correct (the scale is such that it is difficult to be precise but to 
five or six decimals they match) but coordinates for features in the 
raster are wrong; suggesting that the raster projection has "moved" 
rather than the polygons.

The Farm Keeper software seems to not accept the embedded georeferencing 
in the raster as it insists on prompting the user to re-enter 
georeferencing points.

It then generates the polygons in what looks like 28354 (Zone 54 
eastings/northings). These are transformed to 4283 for storage in the 
database.

The map uses:
    PROJECTION
        "proj=eqc"
        "lon_0=139.591e"
    END
where lon_0 has been calculated as the longitude of the centre of the 
requested MBR.

HTH,
Stephen

On Friday 15 June 2007 10:30, Delfos, Jacob wrote:
> Stephen,
>
> I'm not completely clear about what has happened to your raster. Can
> you please clarify whether it appears either moved, or stretched?
> Also, which projection were you polygons in to begin with? Can you
> please tell me:
> - the projection of your polygons
> - the projection of your map
>
> Your raster is in MGA94 (UTM zone 54, GDA datum), which is the common
> Australian projection, so that's probably fine.
>
> Regards,
>
> Jacob
>
> > -----Original Message-----
> > From: UMN MapServer Users List
> > [mailto:MAPSERVER-USERS at LISTS.UMN.EDU] On Behalf Of Stephen Davies
> > Sent: 15 June 2007 08:13
> > To: MAPSERVER-USERS at LISTS.UMN.EDU
> > Subject: [UMN_MAPSERVER-USERS] Image projection question
> >
> > G'day.
> > I posted the following last week but had no response. I am
> > still stuck
> > without any solution so would really appreciate any feedback
> > at all as
> > to what might be wrong with my setup.
> >
> >
> > I have a georeferenced TIFF aerial photo with the gdalinfo below.
> >
> > Using a package called Farm Keeper, a shape file was created (by
> > clicking on the image) containing several polygons defining
> > paddocks. The shape file was then loaded into PostGIS using
> > shp2pgsql and the results displayed with MapServer using the
> > original geotiff as the raster layer.
> >
> > The result was "almost right" except each of the polygons was
> > displayed
> > about 20m due north of it's correct position relative to the
> > raster.
> >
> > The polygon data is stored transformed to SRID 4283. The map
> > projection
> > is eqc with a central meridian of the centre of the polygons' MBR
> > and the map extent is the MBR plus approx 100m - slightly smaller
> > than the
> > raster image extent.
> >
> > Looking at the Map Server map coordinates, it appears that
> > the polygons
> > are correctly positioned (the mouse coordinates displayed match the
> > originals) but the raster has been "moved" (stretched north/south).
> >
> > Can anybody suggest what has happened?
> >
> > Cheers and thanks,
> > Stephen Davies
> >
> >
> > Driver: GTiff/GeoTIFF
> > Size is 600, 448
> > Coordinate System is:
> > PROJCS["GDA94 / MGA zone 54",
> >     GEOGCS["GDA94",
> >         DATUM["Geocentric_Datum_of_Australia_1994",
> >             SPHEROID["GRS 1980",6378137,298.2572221010042,
> >                 AUTHORITY["EPSG","7019"]],
> >             AUTHORITY["EPSG","6283"]],
> >         PRIMEM["Greenwich",0],
> >         UNIT["degree (supplier to define
> > representation)",0.01745329251994328],
> >         AUTHORITY["EPSG","4283"]],
> >     PROJECTION["Transverse_Mercator"],
> >     PARAMETER["latitude_of_origin",0],
> >     PARAMETER["central_meridian",141],
> >     PARAMETER["scale_factor",0.9996],
> >     PARAMETER["false_easting",500000],
> >     PARAMETER["false_northing",10000000],
> >     UNIT["metre",1,
> >         AUTHORITY["EPSG","9001"]],
> >     AUTHORITY["EPSG","28354"]]
> > Origin = (370139.138699,6182407.307100)
> > Pixel Size = (2.00000000,-2.00000000)
> > Metadata:
> >   AREA_OR_POINT=Area
> >   TIFFTAG_DOCUMENTNAME=ER Mapper 7.0
> >   TIFFTAG_IMAGEDESCRIPTION=ER Mapper GeoTiff raster translator
> > V1.0: Band 1 = Red, Band 2 = Green, Band 3 = Blue
> >   TIFFTAG_SOFTWARE=ER Mapper 7.0
> >   TIFFTAG_XRESOLUTION=0
> >   TIFFTAG_YRESOLUTION=0
> > Corner Coordinates:
> > Upper Left  (  370139.139, 6182407.307) (139d35'8.28"E,
> > 34d29'30.38"S) Lower Left  (  370139.139, 6181511.307)
> > (139d35'7.79"E, 34d29'59.46"S) Upper Right (  371339.139,
> > 6182407.307) (139d35'55.32"E,
> > 34d29'30.92"S)
> > Lower Right (  371339.139, 6181511.307) (139d35'54.84"E,
> > 34d30'0.00"S) Center      (  370739.139, 6181959.307)
> > (139d35'31.56"E,
> > 34d29'45.19"S)
> > Band 1 Block=600x20 Type=Byte, ColorInterp=Red
> > Band 2 Block=600x20 Type=Byte, ColorInterp=Green
> > Band 3 Block=600x20 Type=Byte, ColorInterp=Blue
> >
> > --
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> >
> > Stephen Davies Consulting                            Voice:
> > 08-8177 1595
> > Adelaide, South Australia.                             Fax:
> > 08-8177 0133
> > Computing & Network solutions.
> > Mobile:0403 0405 83
>
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This email is for the person(s) identified above, and is confidential to
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Stephen Davies Consulting                            Voice: 08-8177 1595
Adelaide, South Australia.                             Fax: 08-8177 0133
Computing & Network solutions.                       Mobile:0403 0405 83