Projection & raster questions

[Stephen Davies]

I have resolved this issue by rebuilding GEOS, GDAL and mapserv.

It now all works beautifully.

Cheers,
Stephen

On Thur, 1 Dec 2005 05:00 pm, you wrote:
> I have an application which is heavily based on the DHTML rubber band 
> sample in the MapServer tutorial. That is, it used two divs to present 
> a main map and a reference map with mapserv?mode=map commands.
> 
> (MapServer version 4.6.0 OUTPUT=GIF OUTPUT=PNG OUTPUT=JPEG OUTPUT=WBMP 
> OUTPUT=SVG SUPPORTS=PROJ SUPPORTS=FREETYPE SUPPORTS=WMS_SERVER 
> SUPPORTS=GEOS INPUT=TIFF INPUT=EPPL7 INPUT=JPEG INPUT=POSTGIS 
> INPUT=SHAPEFILE)
> 
> The data involved is stored in a PostGIS database as lat/long 
> coordinates and is (currently) projected into the map with proj=eqc 
> lon_0=xxx where xxx is calculated dynamically as the centre of the 
> initial map extent.
> 
> With the attached map1.map mapfile this works very well and users can 
> zoom, pan and query from the main map and pan from the reference map 
> with the correct results (though the area of interest square on the 
> reference map is sometimes marginally out - particularly for very 
small 
> map extents aganst relatively large reference maps).
> 
> The extent for the initial main map is given via the URL in the form:
> 
> 
&mapext=139.357482910156+-34.3308868408203+139.380233764648+-34.3129386901855
> 
> That is, long/lat (calculated dynamically from other input) and the 
> UNITS are meters.
> 
> The values plpl, exex and cidcid are edited to realvalues before 
> invoking mapserv. plpl is the calculated central meridian, cidcid is 
> the current user ID and exex is the extent of the reference map IN 
> METRES!
> 
> This latter extent is calculated from lat/long values using proj:
> 
> proj +proj=eqc +lon_0=$central (where $central is the same value as 
plpl 
> above)
> 
> As I say, the above all works exactly as I want - provided the above 
> projection and extent rules are followed.
> 
> However, I now want to add the raster layer and am having difficulty 
> getting the new layer to align with the rest.
> 
> The raster file is an ECW.
> 
> Driver: ECW/ERMapper Compressed Wavelets
> Size is 82560, 70380
> Coordinate System is:
> GEOGCS["GEOCENTRIC DATUM of AUSTRALIA",
>     DATUM["GDA94",
>         SPHEROID["GRS80",6378137,298.257222101]],
>     PRIMEM["Greenwich",0],
>     UNIT["degree",0.0174532925199433]]
> Origin = (112.500000,-8.903313)
> Pixel Size = (0.00050000,-0.00050000)
> Corner Coordinates:
> Upper Left  ( 112.5000000,  -8.9033134) (112d30'0.00"E,  8d54'11.93"S)
> Lower Left  ( 112.5000000, -44.0933134) (112d30'0.00"E, 44d 5'35.93"S)
> Upper Right ( 153.7800000,  -8.9033134) (153d46'48.00"E,  
8d54'11.93"S)
> Lower Right ( 153.7800000, -44.0933134) (153d46'48.00"E, 44d 
5'35.93"S)
> Center      ( 133.1400000, -26.4983134) (133d 8'24.00"E, 
26d29'53.93"S)
> Band 1 Block=82560x1 Type=Byte, ColorInterp=Red
>   Overviews: arbitrary
> Band 2 Block=82560x1 Type=Byte, ColorInterp=Green
>   Overviews: arbitrary
> Band 3 Block=82560x1 Type=Byte, ColorInterp=Blue
>   Overviews: arbitrary
> 
> To test the ECW raster facility, I created a test map file (attached 
as 
> map2.map).
> 
> The only ways that I could get the image displayed were to specify the 
> projection as epsq:4263 and the extent as lat/long or the projection 
as 
> eqc and the extent in meters relative to 0,0 at top left despite the 
> image georef stuff all being in lat/long (why is this??).
> 
> Neither of these combinations will work in the existing application 
(as 
> the rubber band and reference map interfaces require metres and a 
> proper geographic extent) so I went back to square one with that app 
> and tried again to specify the map extent in metres.
> I used proj to convert the lat/long extent into metres and tried to 
> generate a map. At first it looked as if the map was blank but then I 
> randomly panned around and discovered that the data was actually there 
> but off the map. Apparently, the extent values out of the proj command 
> differ quite significantly from the same values generated within 
> mapserv????
> 
> For example, proj gave me values of -1282.08, -3821696.8 & 
> 1250.54,-3819699 while mapserv gave -1336.4, -3802151 & 1351.1, 
> -3799464 for approximately the same piece of space.
> 
> So, I now have two problems:
> 1. how to calculate the correct extent values for the base app and
> 2. how to get the raster layer to align with the rest (that is with 
the 
> same extent as the rest rather than the 0,0-based one).
> 
> TIA,
> Stephen avies
> 
> -- 
> 
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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
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