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Diffstat (limited to 'docs/source/apps/geod.rst')
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diff --git a/docs/source/apps/geod.rst b/docs/source/apps/geod.rst index 3b60f461..f5e61de4 100644 --- a/docs/source/apps/geod.rst +++ b/docs/source/apps/geod.rst @@ -7,23 +7,23 @@ geod Synopsis ******** - **geod** *+ellps=<ellipse>* [ **-afFIlptwW** [ args ] ] [ *+args* ] file[s] + **geod** *+ellps=<ellipse>* [ **-afFIlptwW** [ args ] ] [ *+args* ] file[s] - **invgeod** *+ellps=<ellipse>* [ **-afFIlptwW** [ args ] ] [ *+args* ] file[s] + **invgeod** *+ellps=<ellipse>* [ **-afFIlptwW** [ args ] ] [ *+args* ] file[s] 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 +: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 +: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: @@ -35,16 +35,16 @@ The following command-line options can appear in any order: .. option:: -I Specifies that the inverse geodesic computation is to be performed. May be - used with execution of geod as an alternative to invgeod execution. + 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. + back azimuths and distance are output. -.. option:: -ta +.. option:: -t<a> - A specifies a character employed as the first character to denote a control + Where *a* specifies a character employed as the first character to denote a control line to be passed through without processing. .. option:: -le @@ -54,29 +54,29 @@ The following command-line options can appear in any order: .. option:: -lu - Gives a listing of all the units that may be selected with the *+units=* + Gives a listing of all the units that may be selected with the *+units=* option. .. option:: -f <format> - Format is a printf format string to control the output form of the + 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. + coordinates and ``"%.3f"`` for distance. .. option:: -F <format> - Format is a printf format string to control the output form of the distance + 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. + ``"%.3f"`` for distance. .. option:: -w<n> - N is the number of significant fractional digits to employ for seconds + 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> - N is the number of significant fractional digits to employ for seconds + 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. @@ -85,15 +85,15 @@ The following command-line options can appear in any order: This option causes the azimuthal values to be output as unsigned DMS numbers between 0 and 360 degrees. Also note :option:`-f`. -The *+args* 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 *+args* 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 + See :ref:`projections_intro` for full list of these parameters and controls. .. only:: man @@ -101,88 +101,88 @@ the first occurrence assumed to be the desired value. 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, +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, +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 +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 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 +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 +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. -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 +: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 +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 +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. +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 + 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 + -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 +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 + 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" + 45d31'0.003"N 123d40'59.985"W 75d39'13.094" .. note:: - Lack of precision in the distance value compromises the + Lack of precision in the distance value compromises the precision of the Portland location. Further reading |