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GEOD(1)				     PROJ			       GEOD(1)

       geod - Geodesic computations

	  geod +ellps=_ellipse_	[-afFIlptwW [args]] [+opt[=arg]	...] file ...

	  invgeod  +ellps=_ellipse_  [-afFIlptwW [args]] [+opt[=arg] ...] file

       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 flatten-

       invgeod may not be available on all platforms; in this case use geod -I

       The following command-line options can appear in	any order:

       -I     Specifies	 that  the  inverse geodesic computation is to be per-
	      formed. May be used with execution of geod as an alternative  to
	      invgeod execution.

       -a     Latitude and longitudes of the initial and terminal points, for-
	      ward 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.

       -f <format>
	      Where  format  is	 a  printf format string to control the	output
	      form of the geographic coordinate	values.	The  default  mode  is
	      DMS for geographic coordinates and "%.3f"	for distance.

       -F <format>
	      Where  format  is	 a  printf format string to control the	output
	      form of the distance value (-F). The default mode	is DMS for ge-
	      ographic coordinates and "%.3f" for distance.

       -w<n>  Where n is the number of significant fractional digits to	employ
	      for seconds output (when the option is not specified, -w3	is as-

       -W<n>  Where n is the number of significant fractional digits to	employ
	      for seconds output. When -W is employed the fields will be  con-
	      stant 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 de-
       sired value.

       See the PROJ documentation for a	full list of these parameters and con-

       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 for-
       ward 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 ra-
       dius units. The latitude	must lie in the	range [-90d,90d]. Output  geo-
       graphic	coordinates  will be in	DMS (if	the -f switch is not employed)
       to 0.001" with trailing,	zero-valued minute-second fields deleted. Out-
       put  distance data will be in the same units as the ellipsoid or	sphere

       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	speci-
       fied with +lat_1=lat and	+lon_1=lon parameters and  either  a  terminus
       point +lat_2=lat	and +lon_2=lon or a distance and azimuth from the ini-
       tial point with +S=distance and +A=azimuth must be specified.

       If points along a geodesic are to be determined then either  +n_S=inte-
       ger 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	deter-

       The  following  script determines the geodesic azimuths and distance in
       U.S.  statute miles from	Boston,	MA, to Portland, OR:

	  geod +ellps=clrk66 <<EOF -I +units=us-mi
	  42d15'N 71d07'W 45d31'N 123d41'W

       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 <<EOF +units=us-mi
	  42d15'N 71d07'W -66d31'50.141" 2587.504

       which gives:

	  45d31'0.003"N	123d40'59.985"W	75d39'13.094"

	  Lack of precision in the distance value compromises the precision of
	  the Portland location.

       1. GeographicLib.

       2. C.  F.  F. Karney, Algorithms	for Geodesics, J. Geodesy 87(1), 43a55
	  (2013); addenda.

       3. A geodesic bibliography.

       proj(1),	cs2cs(1), cct(1), geod(1), gie(1)

       A     list     of     know     bugs	can	 be	 found	    at  where new bug reports can be sub-
       mitted to.


       Charles Karney


6.3.1				 Feb 10, 2020			       GEOD(1)


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