NAME

       geod - direct geodesic computations
       invgeod - inverse geodesic computations

SYNOPSIS

       geod +ellps=<ellipse> [ -afFIlptwW [ args ] ] [ +args ] file[s]
       invgeod +ellps=<ellipse> [ -afFIlptwW [ args ] ] [ +args ] file[s]

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 following runline control parameters can appear in any order:

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

       -a     Latitude  and  longitudes  of  the  initial  and  terminal points, forward and back
              azimuths and distance are output.

       -ta    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|F] format
              Format  is  a  printf  format  string  to control the output form of the geographic
              coordinate values (f)  or  distance  value  (F).   The  default  mode  is  DMS  for
              geographic coordinates and "%.3f" for distance.

       -[w|W]n
              N is the number of significant fractional digits to employ for seconds output (when
              the option is not specified, -w3 is assumed).  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 +args run-line arguments are associated with geodetic parameters  for  specifying  the
       ellipsoidal  or  sphere  to use.  See proj documentation for full list of these parameters
       and controls.  The options are processed in  left  to  right  order  from  the  run  line.
       Reentry of an option is ignored with the first occurrence assumed to be the desired value.

       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 DMS
       format and input distance data must be in units consistent with the ellipsoid  major  axis
       or sphere radius units.  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=lon  parameters  and
       either  a  terminus  point  +lat_2=lat  and  +lon_2=lon 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.

EXAMPLE

       The following script determines the geodesic azimuths and distance in U.S.  stature  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.

SEE ALSO

       Thomas, P.D., 1970, Spheroidal Geodesics, Reference Systems & Local Geometry:  U.S.  Naval
       Oceanographic  Office, S-138.

HOME PAGE

       http://www.remotesensing.org/proj

                                       2000/03/21 Rel. 4.4                                GEOD(1)