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.TH GEOD 1 "2000/03/21 Rel. 4.4"
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geod \- direct geodesic computations
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invgeod \- inverse geodesic computations
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perform geodesic (\*(lqGreat Circle\*(rq) computations for determining
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latitude, longitude and back azimuth of a terminus point
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given a initial point latitude, longitude, azimuth and distance (direct) or
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the forward and back azimuths and distance between an initial and
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terminus point latitudes and longitudes (inverse).
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The following runline control parameters can appear in any order:
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Specifies that the inverse geodesic computation is to be performed.
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May be used with execution of
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Latitude and longitudes of the initial and terminal points,
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forward and back azimuths and distance are output.
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specifies a character employed as the first character to denote
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a control line to be passed through without processing.
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Gives a listing of all the ellipsoids that may be selected with the
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Gives a listing of all the units that may be selected with the
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format string to control the output form of the geographic coordinate values
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(\fBf\fR) or distance value (\fBF\fR).
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The default mode is DMS for geographic coordinates and "%.3f" for distance.
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is the number of significant fractional digits to employ for
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seconds output (when the option is not specified,
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is employed the fields will be constant width with leading zeroes.
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This option causes the azimuthal values to be output as unsigned
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DMS numbers between 0 and 360 degrees. Also note -f.
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run-line arguments are associated with geodetic parameters
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for specifying the ellipsoidal or sphere to use.
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documentation for full list of these parameters and controls.
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The options are processed in left to right order
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Reentry of an option is ignored with the first occurrence assumed to
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be the desired value.
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(processed in left to right order)
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specify the source of data to be transformed.
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A \- will specify the location of processing standard input.
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If no files are specified, the input is assumed to be from
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For direct determinations input data must be in latitude,
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longitude, azimuth and distance order and output will be
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latitude, longitude and back azimuth of the terminus point.
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Latitude, longitude of the initial and terminus point are
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input for the inverse mode and respective forward and back
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azimuth from the initial and terminus points are output along
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with the distance between the points.
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Input geographic coordinates
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(latitude and longitude) and azimuthal data must be in DMS format and input
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distance data must be in units consistent with the ellipsoid
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major axis or sphere radius units.
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Output geographic coordinates will be in DMS
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switch is not employed) to 0.001"
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with trailing, zero-valued minute-second fields deleted.
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Output distance data will be in the same units as the ellipsoid or
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The Earth's ellipsoidal figure may be selected in the same
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.B "+ellps=, +a=, +es=,"
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may also be used to determine intermediate points along either
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a geodesic line between two points or along an arc of specified distance
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from a geographic point.
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In both cases an initial point must be specified with
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parameters and either a terminus point
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or a distance and azimuth from the initial point with
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If points along a geodesic are to be determined then either
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specifying the number of intermediate points and/or
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specifying the incremental distance between points must be specified.
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To determine points along an arc equidistant from the initial point both
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must be specified which determine the respective angular increments
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and number of points to be determined.
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The following script determines the geodesic azimuths and distance in
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U.S. stature miles from Boston, MA, to Portland, OR:
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\f(CWgeod +ellps=clrk66 <<EOF -I +units=us-mi
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42d15'N 71d07'W 45d31'N 123d41'W
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which gives the results:
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\f(CW-66d31'50.141" 75d39'13.083" 2587.504
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where the first two values are the
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azimuth from Boston to Portland, the back azimuth from Portland to
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Boston followed by the distance.
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An example of forward geodesic use is to use the Boston location and determine
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Portland's location by azimuth and distance:
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\f(CWgeod +ellps=clrk66 <<EOF +units=us-mi
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42d15'N 71d07'W -66d31'50.141" 2587.504
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\f(CW45d31'0.003"N 123d40'59.985"W 75d39'13.094"\fR
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Note: lack of precision in the distance value compromises
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the precision of the Portland location.
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.I "Spheroidal Geodesics, Reference Systems & Local Geometry:"
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U.S. Naval Oceanographic Office, S-138.
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http://www.remotesensing.org/proj
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.pc/hyphen-used-as-minus-sign.patch/man/man1/geod.1
