[OSRS-PROJ] WGS84/GEODETIC Projection

[Frank Warmerdam]

Brian Hall wrote:
> 
> Hiya!
> 
> Thanks for the quick reply!!
> 
> We are trying to translate lat/long pairs (in degrees) to x,y coordinates
> (in feet) to be used by our 3D Graphics environment.
> 
> This is our current setup:
> 
>         char longMerd[20];
> 
>         if (point._long > 0.0)
>                 sprintf(longMerd, "+lon_0=%de", (int)point._long);
>         else
>                 sprintf(longMerd, "+lon_0=%dw", (int)abs(point._long));
> 
>         char *args[] = {"proj=utm", "ellps=clrk66", longMerd};
> 
>         _projection = pj_init(3,args);
> 
>       for(;;) // all points to project
>         {
>                 UV projectCoords;
> 
>                 projectCoords.u = DEG2RAD(point._long);
>                 projectCoords.v = DEG2RAD(point._lat);
>                 projectCoords   = pj_fwd(projectCoords, _projection);
> 
>                 x = projectCoords.u
>                 y = projectCoords.v
>         }
> 
> This is working great except now we have some images that we are drawing
> paths on that are in the WGS84/GEODETIC projection.  We would like to just
> change out the projection to use this projection instead of Clark 1866.

Brian, 

Technically you are just operating in a different ellipse, not a different
projection.  You should use "ellps=WGS84" instead of "ellps=clrk66" for WGS84.
A full list of supported ellipses can be extracted from the proj commandline
program with the -le switch. 

ie. 
warmerda at cs46980-c[292]% proj -le
    MERIT a=6378137.0      rf=298.257       MERIT 1983
    SGS85 a=6378136.0      rf=298.257       Soviet Geodetic System 85
    GRS80 a=6378137.0      rf=298.257222101 GRS 1980(IUGG, 1980)
    IAU76 a=6378140.0      rf=298.257       IAU 1976
     airy a=6377563.396    b=6356256.910    Airy 1830
   APL4.9 a=6378137.0.     rf=298.25        Appl. Physics. 1965
    NWL9D a=6378145.0.     rf=298.25        Naval Weapons Lab., 1965
 mod_airy a=6377340.189    b=6356034.446    Modified Airy
   andrae a=6377104.43     rf=300.0         Andrae 1876 (Den., Iclnd.)
  aust_SA a=6378160.0      rf=298.25        Australian Natl & S. Amer. 1969
    GRS67 a=6378160.0      rf=298.2471674270 GRS 67(IUGG 1967)
   bessel a=6377397.155    rf=299.1528128   Bessel 1841
 bess_nam a=6377483.865    rf=299.1528128   Bessel 1841 (Namibia)
   clrk66 a=6378206.4      b=6356583.8      Clarke 1866
   clrk80 a=6378249.145    rf=293.4663      Clarke 1880 mod.
      CPM a=6375738.7      rf=334.29        Comm. des Poids et Mesures 1799
   delmbr a=6376428.       rf=311.5         Delambre 1810 (Belgium)
  engelis a=6378136.05     rf=298.2566      Engelis 1985
  evrst30 a=6377276.345    rf=300.8017      Everest 1830
  evrst48 a=6377304.063    rf=300.8017      Everest 1948
  evrst56 a=6377301.243    rf=300.8017      Everest 1956
  evrst69 a=6377295.664    rf=300.8017      Everest 1969
  evrstSS a=6377298.556    rf=300.8017      Everest (Sabah & Sarawak)
  fschr60 a=6378166.       rf=298.3         Fischer (Mercury Datum) 1960
 fschr60m a=6378155.       rf=298.3         Modified Fischer 1960
  fschr68 a=6378150.       rf=298.3         Fischer 1968
  helmert a=6378200.       rf=298.3         Helmert 1906
    hough a=6378270.0      rf=297.          Hough
     intl a=6378388.0      rf=297.          International 1909 (Hayford)
    krass a=6378245.0      rf=298.3         Krassovsky, 1942
    kaula a=6378163.       rf=298.24        Kaula 1961
    lerch a=6378139.       rf=298.257       Lerch 1979
    mprts a=6397300.       rf=191.          Maupertius 1738
 new_intl a=6378157.5      b=6356772.2      New International 1967
  plessis a=6376523.       b=6355863.       Plessis 1817 (France)
   SEasia a=6378155.0      b=6356773.3205   Southeast Asia
  walbeck a=6376896.0      b=6355834.8467   Walbeck
    WGS60 a=6378165.0      rf=298.3         WGS 60
    WGS66 a=6378145.0      rf=298.25        WGS 66
    WGS72 a=6378135.0      rf=298.26        WGS 72
    WGS84 a=6378137.0      rf=298.257223563 WGS 84

Best regards,

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