=head1 NAME

GeodesicProj -- perform projections based on geodesics

=head1 SYNOPSIS

B<GeodesicProj> ( B<-z> | B<-c> | B<-g> ) I<lat0> I<lon0> [ B<-r> ]
[ B<-e> I<a> I<f> ]
[ B<--comment-delimiter> I<commentdelim> ]
[ B<--version> | B<-h> | B<--help> ]
[ B<--input-file> I<infile> | B<--input-string> I<instring> ]
[ B<--line-separator> I<linesep> ]
[ B<--output-file> I<outfile> ]

=head1 DESCRIPTION

Perform projections based on geodesics.  Convert geodetic coordinates to
either azimuthal equidistant, Cassini-Soldner, or gnomonic coordinates.
The center of the projection (I<lat0>, I<lon0>) is specified by either the B<-c>
option (for Cassini-Soldner), the B<-z> option (for azimuthal equidistant),
or the B<-g> option (for gnomonic).  At least one of these options must be
given (the last one given is used).

Geodetic coordinates are provided on standard input as a set of lines
containing (blank separated) I<latitude> and I<longitude> (decimal
degrees or degrees, minutes, seconds).  For each set of geodetic
coordinates, the corresponding projected coordinates I<x>, I<y> (meters)
are printed on standard output together with the azimuth I<azi>
(degrees) and reciprocal scale I<rk>.  For Cassini-Soldner, I<azi> is
the bearing of the easting direction and the scale in the easting
direction is 1 and the scale in the northing direction is 1/I<rk>.  For
azimuthal equidistant and gnomonic, I<azi> is the bearing of the radial
direction and the scale in the azimuthal direction is 1/I<rk>.  For
azimuthal equidistant and gnomonic, the scales in the radial direction
are 1 and 1/I<rk>^2, respectively.

=head1 OPTIONS

=over

=item B<-z>

use the azimuthal equidistant projection centered at latitude = I<lat0>,
longitude = I<lon0>.

=item B<-c>

use the Cassini-Soldner projection centered at latitude = I<lat0>,
longitude = I<lon0>.

=item B<-g>

use the ellipsoidal gnomonic projection centered at latitude = I<lat0>,
longitude = I<lon0>.

=item B<-r>

perform the reverse projection.  I<x> and I<y> are given on standard
input and each line of standard output gives I<latitude>, I<longitude>,
I<azi>, and I<rk>.

=item B<-e>

specify the ellipsoid via I<a> I<f>; the equatorial radius is I<a> and
the flattening is I<f>.  Setting I<f> = 0 results in a sphere.  Specify
I<f> E<lt> 0 for a prolate ellipsoid.  A simple fraction, e.g., 1/297,
is allowed for I<f>.  (Also, if I<f> E<gt> 1, the flattening is set to
1/I<f>.)  By default, the WGS84 ellipsoid is used, I<a> = 6378137 m,
I<f> = 1/298.257223563.

=item B<--comment-delimiter>

set the comment delimiter to I<commentdelim> (e.g., "#" or "//").  If
set, the input lines will be scanned for this delimiter and, if found,
the delimiter and the rest of the line will be removed prior to
processing and subsequently appended to the output line (separated by a
space).

=item B<--version>

print version and exit.

=item B<-h>

print usage and exit.

=item B<--help>

print full documentation and exit.

=item B<--input-file>

read input from the file I<infile> instead of from standard input; a file
name of "-" stands for standard input.

=item B<--input-string>

read input from the string I<instring> instead of from standard input.
All occurrences of the line separator character (default is a semicolon)
in I<instring> are converted to newlines before the reading begins.

=item B<--line-separator>

set the line separator character to I<linesep>.  By default this is a
semicolon.

=item B<--output-file>

write output to the file I<outfile> instead of to standard output; a
file name of "-" stands for standard output.

=back

=head1 EXAMPLES

   echo 48.648 -2.007 | GeodesicProj -c 48.836 2.337
   => -319919 -11791 86.7 0.999
   echo -319919 -11791 | GeodesicProj -c 48.836 2.337 -r
   => 48.648 -2.007 86.7 0.999

=head1 ERRORS

An illegal line of input will print an error message to standard output
beginning with C<ERROR:> and causes B<GeodesicProj> to return an exit
code of 1.  However, an error does not cause B<GeodesicProj> to
terminate; following lines will be converted.

=head1 SEE ALSO

The ellipsoidal gnomonic projection is derived in Section 8 of
C. F. F. Karney, I<Algorithms for geodesics>, J. Geodesy 87, 43-55 (2013); DOI
L<http://dx.doi.org/10.1007/s00190-012-0578-z>;
addenda: L<http://geographiclib.sf.net/geod-addenda.html>.

=head1 AUTHOR

B<GeodesicProj> was written by Charles Karney.

=head1 HISTORY

B<GeodesicProj> was added to GeographicLib,
L<http://geographiclib.sf.net>, in 2009-08.  Prior to version 1.9 it was
called EquidistantTest.
