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/*! \mainpage PROJ.4 Programmer's Manual
<h2>PROJ.4 Programmer's Manual</h2>
<a href="http://trac.osgeo.org/proj/">PROJ.4 - Cartographic Projections Library</a>
<h3>DESCRIPTION</h3>
Procedure pj_init selects and initializes a cartographic projection with its
argument control parameters. Argc is the number of elements in the array of
control strings argv that each contain individual cartographic control keyword
assignments (+ proj arguments). The list must contain at least the
proj=projection and Earth's radius or elliptical parameters. If the
initialization of the projection is successful a valid address is returned
otherwise a NULL value.
The pj_init_plus function operates similarly to pj_init but takes a single
string containing the definition, with each parameter prefixed with a plus sign.
For example "+proj=utm +zone=11 +ellps=WGS84".
Once initialization is performed either forward or inverse projections can be
performed with the returned value of pj_init used as the argument proj. The
argument structure projUV values u and v contain respective longitude and
latitude or x and y. Latitude and longitude are in radians. If a projection
operation fails, both elements of projUV are set to HUGE_VAL (defined in
math.h).
Note: all projections have a forward mode, but some do not have an inverse
projection. If the projection does not have an inverse the projPJ structure element
inv will be NULL.
The pj_transform function may be used to transform points between the two
provided coordinate systems. In addition to converting between cartographic
projection coordinates and geographic coordinates, this function also takes care
of datum shifts if possible between the source and destination coordinate
system. Unlike pj_fwd and pj_inv it is also allowable for the coordinate system
definitions (projPJ *) to be geographic coordinate systems (defined as
+proj=latlong). The x, y and z arrays contain the input values of the points,
and are replaced with the output values. The function returns zero on success,
or the error number (also in pj_errno) on failure.
Memory associated with the projection may be freed with pj_free.
<h3>EXAMPLE</h3>
The following program reads latitude and longitude
values in decimal degress, performs Mercator
projection with a Clarke 1866 ellipsoid and
a 33° latitude of true scale and prints the projected
cartesian values in meters:
\verbatim
#include <proj_api.h>
main(int argc, char **argv) {
char *args[] = { "proj=merc", "ellps=clrk66", "lat_ts=33" };
projUV p;
projPJ pj;
if (!(pj = pj_init(3, args)))
exit(1);
while (scanf("%lf %lf", &p.v, &p.u) == 2) {
p.u *= DEG_TO_RAD;
p.v *= DEG_TO_RAD;
p = pj_fwd(p, pj);
printf("%.2f\t%.2f\n", p.u, p.v);
}
exit(0);
}
\endverbatim
<h3>API Functions</h3>
XY pj_fwd( LP lp, PJ *P );
LP pj_inv( XY xy, PJ *P );
int pj_transform( PJ *srcdefn, PJ *dstdefn, long point_count, int point_offset, double *x, double *y, double *z );
int pj_datum_transform( PJ *srcdefn, PJ *dstdefn, long point_count, int point_offset, double *x, double *y, double *z );
int pj_compare_datums( PJ *srcdefn, PJ *dstdefn );
int pj_geocentric_to_geodetic( double a, double es, long point_count, int point_offset, double *x, double *y, double *z );
int pj_geodetic_to_geocentric( double a, double es, long point_count, int point_offset, double *x, double *y, double *z );
int pj_apply_gridshift( const char *nadgrids, int inverse, long point_count, int point_offset, double *x, double *y, double *z );
void pj_deallocate_grids( void );
int pj_is_latlong( PJ *pj );
int pj_is_geocent( PJ *pj );
void pj_pr_list( PJ *P );
void pj_set_finder( const char *(*new_finder)(const char *) );
void pj_set_searchpath ( int count, const char **path );
projPJ pj_init(int, char **);
projPJ pj_init_plus(const char *);
char *pj_get_def( projPJ, int );
projPJ pj_latlong_from_proj( PJ *pj_in );
void *pj_malloc( size_t );
void pj_dalloc( void * );
void pj_free( PJ *P );
char *pj_strerrno( int );
int *pj_get_errno_ref( void );
const char *pj_get_release( void );
<h3>SEE ALSO</h3>
<h3>Documentation</h3>
<ul>
<li><a href="http://pubs.er.usgs.gov/usgspubs/pp/pp1395">Snyder, 1987: Map projections; a working manual</a>.
</li>
<li><a href="http://www.asprs.org/resources/GRIDS/">Grids & Datums</a>: Clifford J. Mugnier's columns in PE&RS.
</li>
<li><a href="http://www.mapref.org">MapRef</a>: Assorted general information on projections, and related topics.
</li>
<li><a href="http://earth-info.nga.mil/GandG/publications/index.htm">NGA Publications on Geodesy</a>.
</li>
<li><a href="http://www.progonos.com/furuti/MapProj/CartIndex/cartIndex.html">Map projections</a>: An introduction to cartography emphasizing map projections: their properties, applications and basic mathematics.
</li>
<li><a href="http://www.galleryofmapprojections.com/">Paul B. Anderson's Map Projections Site</a>.
</li>
</ul>
<h3>Software</h3>
<ul>
<li><a href="http://ftp.dfg.ca.gov/Public/BDB/Tools/proj4/proj_api.zip">PROJ.4 VB Wrappers</a> from Eric G. Miller.</li>
<li><a href="http://www.proj4js.org/">PROJ4JS</a> - Javascript projections implementation.</li>
<li><a href="http://gmt.soest.hawaii.edu/">GMT</a> - Generic Mapping Tools, includes reprojection services.</li>
<li><a href="http://edc.usgs.gov/pub/software/gctpc/">GCTPC</a>: The other widely used projection package from the USGS.</li>
<li><a href="http://earth-info.nga.mil/GandG/geotrans/index.htm">Geotrans</a>: a projections and datum shift program from NIMA/NGA.</li>
<li><a href="http://www.jhlabs.com/java/maps/proj/">JHLabs Java Map Projection Library</a>: Loosely derived from PROJ.4 with similar syntax.</li>
<li><a href="http://geotools.org/">GeoTools</a>: GeoTools is a Java GIS library that includes sophisticated projections support.</li>
</ul>
*/
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