Image projection question

[Delfos, Jacob]

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: 
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> Computing & Network solutions.                       
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