[OSRS-PROJ] Re: PROJ4 Tranverse Mercator South Oriented

Frank Warmerdam warmerda at home.com
Thu Sep 21 15:31:52 EDT 2000


Your file:

PCS = 22289 (South African Coordinate System zone 29)
Projection = 17529 (South African Survey Grid zone 29)
Projection Method: CT_TransvMercator_SouthOrientated
   ProjNatOriginLatGeoKey: 0.000000 (  0d 0' 0.00"N)
   ProjNatOriginLongGeoKey: 29.000000 ( 29d 0' 0.00"E)
   ProjScaleAtNatOriginGeoKey: 1.000000
   ProjFalseEastingGeoKey: 0.000000
   ProjFalseNorthingGeoKey: 0.000000
GCS: 4222/Cape
Datum: 6222/Cape
Ellipsoid: 7013/Clarke 1880 (Arc) (6378249.14,6356514.97)
Prime Meridian: 8901/Greenwich (0.000000/  0d 0' 0.00"E)
Projection Linear Units: 9001/metre (1.000000m)

warmerda at cs46980-c[394]% proj +proj=tmerc +lat_0=0 +lon_0=29.0 +k=1.0
+a=6378249.14 +b=6356514.97
26d47'54.95E 26d41'24.59S
-219134.29      -2954952.67

>From the Descartes output:
Image Bottom Right:
PCS: -219134.2379,-2954952.6029
Lat/Long: 26:41:24.59S 26:47:54.95E

Wow!  They are the same! 

Conveniently your file has no false easting or northing so there is
no issue with the "sign" of that.  For everything else it almost seems as
if there is no difference between TM and TMSO.  However, I kind of wonder if
this is just that Descartes is just treating TM and TMSO as being the same.

Can you verify if the Descartes corner coordinates in PCS and lat/long 
coordinates make sense when compared with the map surround? 

Best regards,

I set the clouds in motion - turn up   | Frank Warmerdam, warmerda at home.com
light and sound - activate the windows | http://members.home.com/warmerda
and watch the world go round - Rush    | Geospatial Programmer for Rent
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