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geod(1)                              PROJ                              geod(1)




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  flatten-
       ing.

       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  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
              geographic 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
              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 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
       desired value.

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

       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
       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  ellip-
       soid 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  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-
       mined.


EXAMPLES

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

       which gives:

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

       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),  43a55
          (2013); addenda.

       3. A geodesic bibliography.


SEE ALSO

       proj(1), cs2cs(1), cct(1), gie(1), projinfo(1), projsync(1)


BUGS

       A      list      of      know      bugs     can     be     found     at
       https://github.com/OSGeo/PROJ/issues where new bug reports can be  sub-
       mitted to.


HOME PAGE

       https://proj.org/


AUTHOR

       Charles Karney


COPYRIGHT

       1983-2020



7.1.1                             Sep 1, 2020                          geod(1)

proj 7.1.1 - Generated Thu Sep 3 16:18:42 CDT 2020
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