NAME¶

GeodesicProj -- perform projections based on geodesics

SYNOPSIS¶

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

DESCRIPTION¶

Perform projections based on geodesics. Convert geodetic coordinates to either azimuthal equidistant, Cassini-Soldner, or gnomonic coordinates. The center of the projection ( lat0, lon0) is specified by either the -c option (for Cassini-Soldner), the -z option (for azimuthal equidistant), or the -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) latitude and longitude (decimal degrees or degrees, minutes, seconds). For each set of geodetic coordinates, the corresponding projected coordinates x, y (meters) are printed on standard output together with the azimuth azi (degrees) and reciprocal scale rk. For Cassini-Soldner, 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/ rk. For azimuthal equidistant and gnomonic, azi is the bearing of the radial direction and the scale in the azimuthal direction is 1/ rk. For azimuthal equidistant and gnomonic, the scales in the radial direction are 1 and 1/ rk^2, respectively.

OPTIONS¶

-z

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

-c

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

-g

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

-r

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

-e

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

--comment-delimiter

set the comment delimiter to 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).

--version

print version and exit.

-h

print usage and exit.

--help

print full documentation and exit.

--input-file

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

--input-string

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

--line-separator

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

--output-file

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

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

ERRORS¶

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

SEE ALSO¶

The ellipsoidal gnomonic projection is derived in Section 13 of C. F. F. Karney, Geodesics on an ellipsoid of revolution, Feb. 2011; preprint <http://arxiv.org/abs/1102.1215>. See also Section 8 of C. F. F. Karney, Algorithms for geodesics, Sept. 2011; preprint <http://arxiv.org/abs/1109.4448>.

AUTHOR¶

GeodesicProj was written by Charles Karney.

HISTORY¶

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