Provided by: proj-bin_9.5.1-1_amd64 
NAME
geod - Geodesic computations
SYNOPSIS
geod +ellps=<ellipse> [-afFIlptwW [args]] [+opt[=arg] ...] file ...
invgeod +ellps=<ellipse> [-afFIlptwW [args]] [+opt[=arg] ...] file ...
DESCRIPTION
geod (direct) and invgeod (inverse) perform geodesic (Great Circle) computations for determining
latitude, longitude and back azimuth of a terminus point given a initial point latitude, longitude,
azimuth and distance (direct) or the forward and back azimuths and distance between an initial and
terminus point latitudes and longitudes (inverse). The results are accurate to round off for |f| < 1/50,
where f is flattening.
invgeod may not be available on all platforms; in this case use geod -I instead.
The following command-line options can appear in any order:
-I Specifies that the inverse geodesic computation is to be performed. May be used with execution of
geod as an alternative to invgeod execution.
-a Latitude and longitudes of the initial and terminal points, forward and back azimuths and distance
are output.
-t<a> Where a specifies a character employed as the first character to denote a control line to be
passed through without processing.
-le Gives a listing of all the ellipsoids that may be selected with the +ellps= option.
-lu Gives a listing of all the units that may be selected with the +units= option. (Default units are
meters.)
-f <format>
Where format is a printf format string to control the output form of the geographic coordinate
values. The default mode is DMS.
-F <format>
Where format is a printf format string to control the output form of the distance value. The
default mode is "%.3f".
-w<n> Where n is the number of significant fractional digits to employ for seconds output (when the
option is not specified, -w3 is assumed).
-W<n> Where n is the number of significant fractional digits to employ for seconds output. When -W is
employed the fields will be constant width with leading zeroes.
-p This option causes the azimuthal values to be output as unsigned DMS numbers between 0 and 360
degrees. Also note -f.
The +opt command-line options are associated with geodetic parameters for specifying the ellipsoidal or
sphere to use. controls. The options are processed in left to right order from the command line. Reentry
of an option is ignored with the first occurrence assumed to be the desired value.
See the PROJ documentation for a full list of these parameters and controls.
One or more files (processed in left to right order) specify the source of data to be transformed. A -
will specify the location of processing standard input. If no files are specified, the input is assumed
to be from stdin.
For direct determinations input data must be in latitude, longitude, azimuth and distance order and
output will be latitude, longitude and back azimuth of the terminus point. Latitude, longitude of the
initial and terminus point are input for the inverse mode and respective forward and back azimuth from
the initial and terminus points are output along with the distance between the points.
Input geographic coordinates (latitude and longitude) and azimuthal data must be in decimal degrees or
DMS format and input distance data must be in units consistent with the ellipsoid major axis or sphere
radius units. The latitude must lie in the range [-90d,90d]. Output geographic coordinates will be in DMS
(if the -f switch is not employed) to 0.001" with trailing, zero-valued minute-second fields deleted.
Output distance data will be in the same units as the ellipsoid or sphere radius.
The Earth's ellipsoidal figure may be selected in the same manner as program proj by using +ellps=, +a=,
+es=, etc.
geod may also be used to determine intermediate points along either a geodesic line between two points or
along an arc of specified distance from a geographic point. In both cases an initial point must be
specified with +lat_1=lat and +lon_1=long parameters and either a terminus point +lat_2=lat and
+lon_2=long or a distance and azimuth from the initial point with +S=distance and +A=azimuth must be
specified.
If points along a geodesic are to be determined then either +n_S=integer specifying the number of
intermediate points and/or +del_S=distance specifying the incremental distance between points must be
specified.
To determine points along an arc equidistant from the initial point both +del_A=angle and +n_A=integer
must be specified which determine the respective angular increments and number of points to be
determined.
EXAMPLES
The following script determines the geodesic azimuths and distance in U.S. statute miles from Boston,
MA, to Portland, OR:
geod +ellps=clrk66 -I +units=us-mi <<EOF
42d15'N 71d07'W 45d31'N 123d41'W
EOF
which gives the results:
-66d31'50.141" 75d39'13.083" 2587.504
where the first two values are the azimuth from Boston to Portland, the back azimuth from Portland to
Boston followed by the distance.
An example of forward geodesic use is to use the Boston location and determine Portland's location by
azimuth and distance:
geod +ellps=clrk66 +units=us-mi <<EOF
42d15'N 71d07'W -66d31'50.141" 2587.504
EOF
which gives:
45d31'0.003"N 123d40'59.985"W 75d39'13.094"
i.e., the latitude and longitude of Portland, and the back azimuth from Portland to Boston.
NOTE:
Lack of precision in the distance value compromises the precision of the Portland location.
FURTHER READING
1. GeographicLib.
2. C. F. F. Karney, Algorithms for Geodesics, J. Geodesy 87(1), 43–55 (2013); addenda.
3. A geodesic bibliography.
SEE ALSO
proj(1), cs2cs(1), cct(1), gie(1), projinfo(1), projsync(1)
BUGS
A list of known bugs can be found at https://github.com/OSGeo/PROJ/issues where new bug reports can be
submitted to.
HOME PAGE
https://proj.org/
AUTHOR
Charles Karney
COPYRIGHT
1983-2024, PROJ contributors
9.5 01 Dec 2024 GEOD(1)