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diff --git a/_sources/apps/geod.rst.txt b/_sources/apps/geod.rst.txt new file mode 100644 index 00000000..7b8f921f --- /dev/null +++ b/_sources/apps/geod.rst.txt @@ -0,0 +1,203 @@ +.. _geod: + +================================================================================ +geod +================================================================================ + +Synopsis +******** + + **geod** *+ellps=<ellipse>* [**-afFIlptwW** [args]] [*+opt[=arg]* ...] file ... + + **invgeod** *+ellps=<ellipse>* [**-afFIlptwW** [args]] [*+opt[=arg]* ...] file ... + +Description +*********** + +:program:`geod` (direct) and :program:`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 :math:`|f| < 1/50`, where +:math:`f` is flattening. + + +:program:`invgeod` may not be available on all platforms; in this case +use :option:`geod -I` instead. + +The following command-line options can appear in any order: + + +.. program:: geod + + +.. option:: -I + + Specifies that the inverse geodesic computation is to be performed. May be + used with execution of :program:`geod` as an alternative to :program:`invgeod` execution. + +.. option:: -a + + Latitude and longitudes of the initial and terminal points, forward and + back azimuths and distance are output. + +.. option:: -t<a> + + Where *a* specifies a character employed as the first character to denote a control + line to be passed through without processing. + +.. option:: -le + + Gives a listing of all the ellipsoids that may be selected with the + *+ellps=* option. + +.. option:: -lu + + Gives a listing of all the units that may be selected with the *+units=* + option. (Default units are meters.) + +.. 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. + +.. option:: -F <format> + + Where *format* is a printf format string to control the output form of the distance + value. The default mode is ``"%.3f"``. + +.. option:: -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). + +.. option:: -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. + +.. option:: -p + + This option causes the azimuthal values to be output as unsigned DMS + numbers between 0 and 360 degrees. Also note :option:`-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. + +.. only:: html + + See :ref:`projections_intro` for full + list of these parameters and controls. + +.. only:: man + + 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 :option:`-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 :program:`proj` by using *+ellps=*, *+a=*, *+es=*, etc. + +:program:`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. + +Examples +******** + +The following script determines the geodesic azimuths and distance in U.S. +statute miles from Boston, MA, to Portland, OR: + +.. code-block:: console + + geod +ellps=clrk66 <<EOF -I +units=us-mi + 42d15'N 71d07'W 45d31'N 123d41'W + EOF + +which gives the results: + +.. code-block:: console + + -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: + +.. code-block:: console + + geod +ellps=clrk66 <<EOF +units=us-mi + 42d15'N 71d07'W -66d31'50.141" 2587.504 + EOF + +which gives: + +.. code-block:: console + + 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 +*************** + +#. `GeographicLib <https://geographiclib.sourceforge.io>`_. + +#. C. F. F. Karney, `Algorithms for Geodesics <https://doi.org/10.1007/s00190-012-0578-z>`_, J. Geodesy **87**\ (1), 43–55 (2013); + `addenda <https://geographiclib.sourceforge.io/geod-addenda.html>`_. + +#. `A geodesic bibliography <https://geographiclib.sourceforge.io/geodesic-papers/biblio.html>`_. + +.. only:: man + + See also + ******** + + **proj(1)**, **cs2cs(1)**, **cct(1)**, **gie(1)**, **projinfo(1)**, **projsync(1)** + + .. include:: common_man.rst |