Merge pull request #869 from kbevers/sphinx-man-pages

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diff --git a/docs/source/apps/cct.rst b/docs/source/apps/cct.rst
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+.. _cct:
+
+================================================================================
+cct
+================================================================================
+
+.. Index:: cct
+
+.. only:: html
+
+    Coordinate Conversion and Transformation.
+
+Synopsis
+********
+
+       **cct** [ **-cotvz** [ args ] ] *+opts[=arg]*  file[s]
+
+Description
+***********
+
+:program:`cct` a 4D equivalent to the :program:`proj` projection program,
+performs transformation coordinate systems on a set of input points.  The
+coordinate system transformation can include  translation  between projected
+and geographic coordinates as well as the application of datum shifts.
+
+
+The following control parameters can  appear  in any order:
+
+.. program:: cct
+
+.. option:: -c <x,y,z,t>
+
+    Specify input columns for (up to) 4 input parameters. Defaults to 1,2,3,4.
+
+.. option:: -o <output file name>, --output=<output file name>
+
+    Specify the name of the output file.
+
+.. option:: -t <time>, --time=<time>
+
+    Specify a fixed observation time to be used for all input data.
+
+.. option:: -z <height>, --height=<height>
+
+    Specify a fixed observation height to be used for all input data.
+
+.. option:: -v, --verbose
+
+    Write non-essential, but potentially useful, information to stderr.
+    Repeat for additional information (``-vv``, ``-vvv``, etc.)
+
+The *+args* arguments are associated with coordinate operation parameters.
+Usage varies with operation.
+
+.. only:: html
+
+    For a complete description consult the :ref:`projection pages <projections>`.
+
+
+:program:`cct` is an acronym meaning *Coordinate Conversion and Transformation*.
+
+The acronym refers to definitions given in the OGC 08-015r2/ISO-19111
+standard "Geographical Information -- Spatial Referencing by Coordinates",
+which defines two different classes of *coordinate operations*:
+
+*Coordinate Conversions*, which are coordinate operations where input
+and output datum are identical (e.g. conversion from geographical to
+cartesian coordinates) and
+
+*Coordinate Transformations*, which are coordinate operations where
+input and output datums differ (e.g. change of reference frame).
+
+Examples
+********
+
+1. The operator specs describe the action to be performed by :program:`cct`. So
+   the following script
+
+.. code-block:: console
+
+     echo 12 55 0 0 | cct +proj=utm +zone=32 +ellps=GRS80
+
+will transform the input geographic coordinates into UTM zone 32 coordinates.
+Hence, the command
+
+.. code-block:: console
+
+      echo 12 55 | cct -z0 -t0 +proj=utm +zone=32 +ellps=GRS80
+
+Should give results comparable to the classic proj command
+
+.. code-block:: console
+
+      echo 12 55 | proj +proj=utm +zone=32 +ellps=GRS80
+
+2. Convert geographical input to UTM zone 32 on the GRS80 ellipsoid:
+
+.. code-block:: console
+
+      cct +proj=utm +ellps=GRS80 +zone=32
+
+3. Roundtrip accuracy check for the case above:
+
+.. code-block:: console
+
+      cct +proj=pipeline +proj=utm +ellps=GRS80 +zone=32 +step +step +inv
+
+4. As (2) but specify input columns for longitude, latitude, height and time:
+
+.. code-block:: console
+
+      cct -c 5,2,1,4  +proj=utm +ellps=GRS80 +zone=32
+
+5. As (2) but specify fixed height and time, hence needing only 2 cols in
+   input:
+
+.. code-block:: console
+
+      cct -t 0 -z 0  +proj=utm  +ellps=GRS80  +zone=32
+
+
+Background
+**********
+
+:program:`cct` also refers to Carl Christian Tscherning (1942--2014),
+professor of Geodesy at the University of Copenhagen, mentor and advisor
+for a generation of Danish geodesists, colleague and collaborator for
+two generations of global geodesists, Secretary General for the
+International Association of Geodesy, IAG (1995--2007), fellow of the
+American Geophysical Union (1991), recipient of the IAG Levallois Medal
+(2007), the European Geosciences Union Vening Meinesz Medal (2008), and
+of numerous other honours.
+
+*cct*, or Christian, as he was known to most of us, was recognized for his
+good mood, his sharp wit, his tireless work, and his great commitment to
+the development of geodesy -- both through his scientific contributions,
+comprising more than 250 publications, and by his mentoring and teaching
+of the next generations of geodesists.
+
+As Christian was an avid Fortran programmer, and a keen Unix connoisseur,
+he would have enjoyed to know that his initials would be used to name a
+modest Unix style transformation filter, hinting at the tireless aspect
+of his personality, which was certainly one of the reasons he accomplished
+so much, and meant so much to so many people.
+
+Hence, in honour of *cct* (the geodesist) this is :program:`cct` (the program).
+
+
+.. only:: man
+
+    See also
+    ********
+
+    **proj(1)**, **cs2cs(1)**, **geod(1)**, **gie(1)**
+
+    Bugs
+    ****
+
+    A list of know bugs can be found at http://github.com/OSGeo/proj.4/issues
+    where new bug reports can be submitted to.
+
+    Home page
+    *********
+
+    http://proj4.org/
diff --git a/docs/source/apps/cs2cs.rst b/docs/source/apps/cs2cs.rst
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+.. _cs2cs:
+
+================================================================================
+cs2cs
+================================================================================
+
+.. only:: html
+
+    Cartographic coordinate system filter.
+
+Synopsis
+********
+
+   **cs2cs** [ **-eEfIlrstvwW** [ args ] ] [ *+opts[=arg]* ] [ +to [*+opts[=arg]*] ] file[s]
+
+Description
+***********
+
+:program:`cs2cs` performs transformation between the source and destination
+cartographic  coordinate  system on a set of input points.  The coordinate
+system transformation can include  translation  between projected  and
+geographic coordinates as well as the application of datum shifts.
+
+The following control parameters can  appear  in any order:
+
+.. program:: cs2cs
+
+.. option:: -I
+
+    method to specify inverse translation, convert from *+to* coordinate system to
+    the primary coordinate system defined.
+
+.. option:: -t<a>
+
+    A specifies a character employed as the first character to denote a control
+    line to  be passed through without processing. This option  applicable  to
+    ascii  input only. (# is the default value).
+
+.. option:: -e <string>
+
+    String is an arbitrary string to be output if an error is detected  during
+    data transformations. The  default value is: *\t*. Note that if the -b, -i
+    or -o options are employed, an error is returned as HUGE_VAL value for both
+    return values.
+
+.. option:: -E
+
+    causes the input coordinates to be copied to the output line prior to
+    printing  the converted values.
+
+.. option:: -l<[=id]>
+
+    List projection identifiers that can be selected with *+proj*. ``cs2cs -l=id``
+    gives expanded description of projection id, e.g. ``cs2cs -l=merc``.
+
+.. option:: -lp
+
+    List of all projection id that can be used with the *+proj* parameter.
+    Equivalent to ``cs2cs -l``.
+
+.. option:: -lP
+
+    Expanded description of all projections that can be used with the *+proj*
+    parameter.
+
+.. option:: -le
+
+    List of all ellipsoids that can be selected with the *+ellps* parameters.
+
+.. option:: -lu
+
+    List of all distance units that can be selected with the *+units* parameter.
+
+.. option:: -ld
+
+    List of datums that can be selected with the *+datum* parameter.
+
+.. option:: -r
+
+    This options reverses the order of the expected input from
+    longitude-latitude or x-y to latitude-longitude or y-x.
+
+.. option:: -s
+
+    This options reverses the order of the output from x-y or longitude-latitude
+    to y-x or latitude-longitude.
+
+.. option:: -f <format>
+
+    Format is a printf format string to control the form of the output values.
+    For inverse projections, the output will be in degrees when this option is
+    employed.  If a format is specified for inverse projection the output data
+    will be in deci- mal  degrees. The default format is "%.2f" for forward
+    projection and DMS for inverse.
+
+.. option:: -[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 and with leading zeroes.
+
+.. option:: -v
+
+    causes a listing of cartographic control parameters tested for and used by
+    the program to be printed prior to input data.
+
+
+.. only:: man
+
+    The *+args* run-line arguments are associated with cartographic
+    parameters.
+
+.. only:: html
+
+    The *+args* run-line arguments are associated with cartographic
+    parameters.  Usage varies with projection and for a complete description
+    consult the :ref:`projection pages <projections>`.
+
+The :program:`cs2cs` program requires two coordinate system definitions.  The first (or
+primary  is  defined based on all projection parameters not appearing after the
+*+to* argument.  All projection  parameters appearing  after the *+to* argument
+are considered the definition of the second  coordinate system.  If there is no
+second coordinate system defined, a geographic coordinate system based on the
+datum and ellipsoid of the source coordinate system is assumed.  Note  that  the
+source  and destination  coordinate  system can both be projections, both be
+geographic, or one of each and may have the same or different datums.
+
+Additional  projection control parameters may be contained in two auxiliary
+control  files:  the first   is   optionally   referenced   with  the
+*+init=file:id* and the second is always processed after the name of the
+projection has been established from either the run-line or the  contents of
+*+init*   file.   The  environment  parameter PROJ_LIB establishes the default
+directory for a file  reference  without an absolute path.  This is also used
+for  supporting  files  like  datum shift files.
+
+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 input data the two data values  must  be  in the  first  two white space
+separated fields and when both input and output are ASCII all  trailing portions
+of the input line are appended to the output line.
+
+Input geographic data (longitude  and  latitude) must  be  in  DMS  or decimal
+degrees format and input cartesian data must be in units consistent with  the
+ellipsoid major axis or sphere radius units.  Output geographic coordinates will
+normally be in DMS format (use ``-f %.12f`` for decimal degrees with 12 decimal
+places), while projected (cartesian)   coordinates   will  be  in  linear
+(meter, feet) units.
+
+
+Example
+*******
+
+The following script
+
+::
+
+     cs2cs +proj=latlong +datum=NAD83 +to +proj=utm +zone=10  +datum=NAD27 -r
+     <<EOF 45d15'33.1"   111.5W 45d15.551666667N   -111d30 +45.25919444444
+     111d30'000w EOF
+
+will  transform the input NAD83 geographic coordinates into NAD27 coordinates in
+the  UTM  projection  with  zone 10 selected.  The geographic values of this
+example are equivalent and  meant as  examples of various forms of DMS input.
+The x-y output data will appear as three lines of:
+
+::
+
+     1402285.99      5076292.42 0.000
+
+.. only:: man
+
+    See also
+    ********
+
+    **proj(1)**, **cct(1)**, **geod(1)**, **gie(1)**
+
+    Bugs
+    ****
+
+    A list of know bugs can be found at http://github.com/OSGeo/proj.4/issues
+    where new bug reports can be submitted to.
+
+    Home page
+    *********
+
+    http://proj4.org/
diff --git a/docs/source/apps/geod.rst b/docs/source/apps/geod.rst
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+.. _geod:
+
+================================================================================
+geod
+================================================================================
+
+Synopsis
+********
+
+       **geod** *+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
+: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 geod as an alternative to invgeod execution.
+
+.. option:: -a
+
+    Latitude and longitudes of the initial and terminal points, forward and
+    back azimuths and distance are  output.
+
+.. option:: -ta
+
+    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.
+
+.. option:: -f <format>
+
+    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.
+
+.. option:: -F <format>
+
+    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.
+
+.. option:: -w<n>
+
+    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
+    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  *+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
+    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.
+
+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)**, **geod(1)**, **gie(1)**
+
+    Bugs
+    ****
+
+    A list of know bugs can be found at http://github.com/OSGeo/proj.4/issues
+    where new bug reports can be submitted to.
+
+    Home page
+    *********
+
+    http://proj4.org/
diff --git a/docs/source/apps/gie.rst b/docs/source/apps/gie.rst
new file mode 100644
index 00000000..f94c1171
--- /dev/null
+++ b/docs/source/apps/gie.rst
@@ -0,0 +1,311 @@
+.. _gie:
+
+================================================================================
+gie
+================================================================================
+
+.. Index:: gie
+
+.. only:: html
+
+       The Geospatial Integrity Investigation Environment
+
+Synopsis
+********
+
+    **gie** [ **-hovql** [ args ] ] file[s]
+
+Description
+***********
+
+:program:`gie`, the Geospatial Integrity Investigation Environment, is a
+regression testing environment for the PROJ transformation library. Its primary
+design goal is to be able to perform regression testing of code that are a part
+of PROJ, while not requiring any other kind of tooling than the same C compiler
+already employed for compiling the library.
+
+.. option:: -h, --help
+
+    Print usage information
+
+.. option:: -o <file>, --output <file>
+
+    Specify output file name
+
+.. option:: -v, --verbose
+
+    Verbose: Provide non-essential informational output.  Repeat :option:`-v` for
+    more verbosity (e.g. ``-vv``)
+
+.. option:: -q, --quiet
+
+    Quiet: Opposite of verbose. In  quiet  mode  not  even  errors  are
+    reported.  Only  interaction  is through the return code (0 on success,
+    non-zero indicates number of FAILED tests)
+
+.. option:: -l, --list
+
+    List the PROJ internal system error codes
+
+Tests for :program:`gie` are defined in simple text files. Usually having the
+extension ``.gie``. Test for :program:`gie` are written in the purpose-build command language for gie.
+The basic functionality of the gie command language is implemented through just
+3 command verbs: ``operation``, which defines the PROJ operation to test,
+``accept``, which defines the input coordinate to read, and ``expect``, which
+defines the result to expect.
+
+A sample test file for :program:`gie` that uses the three above basic commands looks
+like:
+
+.. code-block:: console
+
+    <gie>
+
+    --------------------------------------------
+    Test output of the UTM projection
+    --------------------------------------------
+    operation  +proj=utm  +zone=32  +ellps=GRS80
+    --------------------------------------------
+    accept     12  55
+    expect     691_875.632_14   6_098_907.825_05
+
+    </gie>
+
+Parsing of a  :program:`gie` file starts at ``<gie>`` and ends when ``</gie>``
+is reached. Anything before ``<gie>`` and after ``</gie>`` is not considered.
+Test cases are created by defining an :option:`operation` which
+:option:`accept` an input coordinate and :option:`expect` an output
+coordinate.
+
+Because :program:`gie` tests are wrapped in the ``<gie>``/``</gie>`` tags it is
+also possible to add test cases to custom made :ref:`init files <init_files>`.
+The tests will be ignore by PROJ when reading the init file with *+init* and
+:program:`gie` ignores anything not wrapped in ``<gie>``/``</gie>``.
+
+:program:`gie` tests are defined by a set of commands like :option:`operation`,
+:option:`accept` and :option:`expect` in the example above. Together the
+commands make out the :program:`gie` command language. Any line in a
+:program:`gie` file that does not start with a command is ignored. In the
+example above it is seen how this can be used to add comments and styling to
+:program:`gie` test files in order to make them more readable as well as
+documenting what the purpose of the various tests are.
+
+Below the :ref:`gie_commands` is explained in details.
+
+Examples
+*********
+
+1. Run all tests in a file with all debug information turned on
+
+.. code-block:: console
+
+    gie -vvvv corner-cases.gie
+
+2. Run all tests in several files
+
+.. code-block:: console
+
+    gie foo bar
+
+.. _gie_commands:
+
+gie command language
+********************
+
+
+.. option:: operation <+args>
+
+    Define a PROJ operation to test. Example:
+
+    .. code-block:: console
+
+        operation proj=utm zone=32 ellps=GRS80
+        # test 4D function
+        accept    12 55 0 0
+        expect    691875.63214  6098907.82501  0  0
+
+        # test 2D function
+        accept    12 56
+        expect    687071.4391   6210141.3267
+
+.. option:: accept <x y [z [t]]>
+
+    Define the input coordinate to read. Takes test coordinate. The coordinate
+    can be defined by either 2, 3 or 4 values, where the first two values are
+    the x- and y-components, the 3rd is the z-component and the 4th is the time
+    component. The number of components in the coordinate determines which
+    version of the operation is tested (2D, 3D or 4D). Many coordinates can be
+    accepted for one :option:`operation`. For each :option:`accept` an
+    accompanying :option:`expect` is needed.
+
+    Note that :program:`gie` accepts the underscore ("_") as a thousands
+    separator.  It is not required (in fact, it is entirely ignored by the
+    input routine), but it significantly improves the readability of the very
+    long strings of numbers typically required in projected coordinates.
+
+
+    See :option:`operation` for an example.
+
+.. option:: expect <x y [z [t]]> | <error code>
+
+    Define the expected coordinate that will be returned from accepted
+    coordinate passed though an operation. The expected coordinate can be
+    defined by either 2, 3 or 4 components, similarly to :option:`accept`.
+    Many coordinates can be expected for one :option:`operation`. For each
+    :option:`expect` an accompanying :option:`accept` is needed.
+
+    See :option:`operation` for an example.
+
+    In addition to expecting a coordinate it is also possible to expect a
+    PROJ error code in case an operation can't be created. This is useful when
+    testing that errors are caught and handled correctly. Below is an example of
+    that tests that the pipeline operator fails correctly when a non-invertable
+    pipeline is constructed.
+
+    .. code-block:: console
+
+        operation   proj=pipeline step
+                    proj=urm5 n=0.5 inv
+        expect      failure pjd_err_malformed_pipeline
+
+    See ``gie -l`` for a list of error codes that can be expected.
+
+.. option:: tolerance <tolerance>
+
+    The :option:`tolerance` command controls how much accepted coordinates
+    can deviate from the expected coordinate. This is handy to test that an
+    operation meets a certain numerical tolerance threshold. Some operations
+    are expexted to be accurate within milimeters  where others might only be
+    accurate within a few meters. :option:`tolerance` should
+
+    .. code-block:: console
+
+        operation       proj=merc
+        # test coordinate as returned by ```echo 12 55 | proj +proj=merc``
+        tolerance       1 cm
+        accept          12 55
+        expect          1335833.89 7326837.72
+
+        # test that the same coordinate with a 50 m false easting as determined
+        # by ``echo 12 55 |proj +proj=merc +x_0=50`` is still within a 100 m
+        # tolerance of the unaltered coordinate from proj=merc
+        tolerance       100 m
+        accept          12 55
+        expect          1335883.89  7326837.72
+
+    The default tolerance is 0.5 mm. See :option:`proj -lu` for a list of possible
+    units.
+
+.. option:: roundtrip <n> <tolerance>
+
+    Do a roundtrip test of an operation. :option:`roundtrip` needs a
+    :option:`operation` and a :option:`accept` command
+    to function. The accepted coordinate is passed to the operation first in
+    it's forward mode, then the output from the forward operation is passed
+    back to the inverse operation. This procedure is done ``n`` times. If the
+    resulting coordinate is within the set tolerance of the initial coordinate
+    the test is passed.
+
+    Example:
+
+    operation       proj=merc
+    accept          12 55
+    roundtrip       10000 5 mm
+
+
+.. option:: direction <direction>
+
+    The :option:`direction` command specifies in which direction an operation
+    is performed. This can either be ``forward`` or ``inverse``. An example of
+    this is seen below where it is tested that a symmetrical transformation
+    pipeline returns the same results in both directions.
+
+    .. code-block:: console
+
+        operation proj=pipeline zone=32 step
+                  proj=utm  ellps=GRS80 step
+                  proj=utm  ellps=GRS80 inv
+        tolerance 0.1 mm
+
+        accept 12 55 0 0
+        expect 12 55 0 0
+
+        # Now the inverse direction (still same result: the pipeline is symmetrical)
+
+        direction inverse
+        expect 12 55 0 0
+
+    The default direction is "forward".
+
+.. option:: ignore <error code>
+
+    This is especially
+    useful in test cases that rely on a grid that is not guaranteed to be
+    available. Below is an example of that situation.
+
+    .. code-block:: console
+
+        operation  proj=hgridshift +grids=nzgd2kgrid0005.gsb  ellps=GRS80
+        tolerance 1 mm
+        ignore    pjd_err_failed_to_load_grid
+        accept    172.999892181021551 -45.001620431954613
+        expect    173                 -45
+
+
+    See ``gie -l`` for a list of error codes that can be ignored.
+
+
+Background
+**********
+
+More importantly than being an acronym for "Geospatial Integrity Investigation
+Environment", gie were also the initials, user id, and USGS email address of
+Gerald Ian Evenden (1935--2016), the geospatial visionary, who, already in the
+1980s, started what was  to  become  the PROJ of today.
+
+Gerald's clear vision was that map projections are *just special functions*.
+Some of them rather complex, most of them of two variables, but all of them
+*just special functions*, and not particularly more special than the :c:func:`sin()`,
+:c:func:`cos()`, :c:func:`tan()`, and :c:func:`hypot()` already available  in  the  C standard library.
+
+And hence, according to Gerald, *they should not be particularly much harder
+to use*, for a programmer, than the :c:func:`sin()`'s, :c:func:`tan()`'s and
+:c:func:`hypot()`'s so readily available.
+
+Gerald's ingenuity also showed in the implementation of the vision, where
+he devised a comprehensive, yet simple, system of key-value pairs for
+parameterising a map projection, and the highly flexible PJ struct, storing
+run-time compiled versions of those key-value pairs, hence mak- ing  a  map
+projection  function call, pj_fwd(PJ, point), as easy as a traditional function
+call like ``hypot(x,y)``.
+
+While today, we may have more formally well defined metadata systems (most
+prominent the OGC WKT2 representation), nothing comes close being as easily
+readable ("human compatible") as Gerald's key-value system. This system in
+particular, and the PROJ system in general, was Gerald's great gift to anyone
+using and/or communicating about geodata.
+
+It is only reasonable to name a program, keeping an eye on the
+integrity of the PROJ system, in honour of Gerald.
+
+So in honour, and hopefully also in the spirit, of Gerald Ian Evenden
+(1935--2016), this is the Geospatial Integrity Investigation Environment.
+
+
+.. only:: man
+
+    See also
+    ********
+
+    **proj(1)**, **cs2cs(1)**, **cct(1)**, **geod(1)**
+
+    Bugs
+    ****
+
+    A list of know bugs can be found at http://github.com/OSGeo/proj.4/issues
+    where new bug reports can be submitted to.
+
+    Home page
+    *********
+
+    http://proj4.org/
diff --git a/docs/source/apps/index.rst b/docs/source/apps/index.rst
new file mode 100644
index 00000000..91f5c4ff
--- /dev/null
+++ b/docs/source/apps/index.rst
@@ -0,0 +1,22 @@
+.. _apps:
+
+================================================================================
+Applications
+================================================================================
+
+Bundled with PROJ comes a set of small command line utilities. The ``proj``
+program is limited to converting between geographic and projection coordinates
+within one datum. The ``cs2cs`` program operates similarly, but allows
+translation between any pair of definable coordinate systems, including support
+for basic datum translation. The ``geod`` program provides the ability to do
+geodesic (great circle) computations. ``gie`` is the program used for
+regression tests in PROJ.
+
+.. toctree::
+   :maxdepth: 1
+
+   proj
+   cct
+   cs2cs
+   geod
+   gie
diff --git a/docs/source/apps/proj.rst b/docs/source/apps/proj.rst
new file mode 100644
index 00000000..dee4ea89
--- /dev/null
+++ b/docs/source/apps/proj.rst
@@ -0,0 +1,236 @@
+.. _proj:
+
+================================================================================
+proj
+================================================================================
+
+.. only:: html
+
+    Cartographic projection filter.
+
+.. Index:: proj
+
+Synopsis
+********
+    **proj** [ **-bceEfiIlmorsStTvVwW** ] [ args ] ] [ *+args* ] file[s]
+
+    **invproj** [ **-bceEfiIlmorsStTwW** ] [ args ] ] [ *+args* ] file[s]
+
+
+Description
+***********
+:program:`proj` and :program:`invproj` perform respective forward  and inverse
+transformation  of cartographic data to or from cartesian data  with  a  wide
+range  of selectable projection functions.
+
+:program:`invproj` may not be available on all  platforms;  in  this  case
+use :option:`proj -I` instead.
+
+The  following  control parameters can appear in any order
+
+.. program:: proj
+
+.. option:: -b
+
+    Special option for binary coordinate data input and output through standard
+    input and standard output. Data is assumed to be in system type double
+    floating point words. This option is to be used when proj is a son process
+    and allows bypassing formatting operations.
+
+.. option:: -i
+
+    Selects binary input only (see :option:`-b`).
+
+.. option:: -I
+
+    alternate method to specify inverse projection. Redundant when used with
+    invproj.
+
+.. option:: -o
+
+    Selects binary output only (see :option:`-b`).
+
+.. option:: -t<a>
+
+    *a* specifies a character employed as the first character to denote a
+    control line to be passed through without  processing. This  option
+    applicable to ascii input only. (# is the default value).
+
+.. option:: -e <string>
+
+      String is an arbitrary string to be output if an error is detected during
+      data transformations. The default value is: *\t*. Note that if the
+      :option:`-b`, :option:`-i` or :option:`-o` options are employed, an error
+      is returned as HUGE_VAL value for both return values.
+
+.. option:: -E
+
+    causes the input coordinates to be copied to the output line prior to
+    printing the converted values.
+
+.. option:: -l<[=id]>
+
+    List projection identifiers that can be selected with *+proj*. ``proj -l=id``
+    gives expanded description of projection id, e.g. ``proj -l=merc``.
+
+.. option:: -lp
+
+    List of all projection id that can be used with the *+proj* parameter.
+    Equivalent to ``proj -l``.
+
+.. option:: -lP
+
+    Expanded description of all projections that can be used with the *+proj*
+    parameter.
+
+.. option:: -le
+
+    List of all ellipsoids that can be selected with the *+ellps* parameters.
+
+.. option:: -lu
+
+    List of all distance units that can be selected with the *+units* parameter.
+
+.. option:: -ld
+
+    List of datums that can be selected with the *+datum* parameter.
+
+
+.. option:: -r
+
+    This options reverses the order of the expected input from
+    longitude-latitude or x-y to latitude-longitude or y-x.
+
+.. option:: -s
+
+    This options reverses the order of the output from x-y or longitude-latitude
+    to y-x or latitude-longitude.
+
+.. option:: -S
+
+    Causes estimation of meridional and parallel scale factors, area scale
+    factor and angular distortion, and maximum and minimum scale factors to be
+    listed between <> for each input point. For conformal projections meridional
+    and parallel scales factors will be equal and angular distortion zero. Equal
+    area projections will have an area factor of 1.
+
+.. option:: -m <mult>
+
+    The cartesian data may be scaled by the mult parameter. When processing data
+    in a forward projection mode the cartesian output values are multiplied by
+    mult otherwise the input cartesian values are divided by mult before inverse
+    projection.  If the first two characters of mult are 1/ or 1: then the
+    reciprocal value of mult is employed.
+
+.. option:: -f <format>
+
+    Format is a printf format string to control the form of the output values.
+    For inverse projections, the output will be in degrees when this option is
+    employed.  The  default format is "%.2f" for forward projection and DMS for
+    inverse.
+
+.. option:: -[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 and  with  leading zeroes.
+
+.. option:: -v
+
+    causes a listing of cartographic control parameters tested for and used by
+    the program to be printed prior to input data. Should not be used with the
+    :option:`-T` option.
+
+.. option:: -V
+
+    This option causes an expanded annotated listing of the characteristics of
+    the projected point. :option:`-v` is implied with this option.
+
+.. option:: -T <ulow,uhi,vlow,vhi,res[,umax,vmax]>
+
+    This option creates a set of bivariate Chebyshev polynomial coefficients
+    that approximate the selected  cartographic projection on stdout. The values
+    low and hi denote the range of the input where the u or v prefixes apply to
+    respective longitude-x or latitude-y depending upon whether a forward or
+    inverse projection is selected. Res is an integer number specifying the
+    power of 10 precision of the approximation. For example, a res of -3
+    specifies an approximation with an accuracy better than .001. Umax, and vmax
+    specify maximum degree of the polynomials (default: 15).
+
+
+
+The *+args* run-line arguments are associated with cartographic parameters.
+Additional projection control parameters may  be contained  in  two  auxiliary
+control files: the first  is   optionally   referenced   with   the
+*+init=file:id* and the second is always processed after the name of the
+projection has been established from either the run-line or the contents of
++init  file.   The   environment   parameter :envvar:`PROJ_LIB` establishes the
+default directory for a file reference without an absolute  path.   This is
+also  used  for  supporting files like datum shift files.
+
+.. only:: html
+
+    Usage of *+args* varies with projection and for a complete description
+    consult the :ref:`projection pages <projections>`.
+
+
+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 ASCII input data the two data values must be in the first two white  space
+separated  fields and  when  both  input  and output are ASCII all trailing
+portions of the input line are appended to the output line.
+
+Input  geographic  data (longitude and latitude) must be in DMS format and input
+cartesian  data must  be  in units consistent with the ellipsoid major axis or
+sphere radius units.  Output geographic  coordinates  will  be in DMS (if the
+``-w`` switch is not employed) and  precise  to  0.001" with  trailing, zero-valued
+minute-second fields deleted.
+
+Example
+*******
+The following script
+
+.. code-block:: console
+
+     proj +proj=utm  +lon_0=112w  +ellps=clrk66
+     -r <<EOF
+     45d15'33.1"   111.5W
+     45d15.551666667N   -111d30
+     +45.25919444444    111d30'000w
+     EOF
+
+will perform UTM forward projection with a standard UTM  central  meridian
+nearest  longitude 112W.  The geographic values of this example are equivalent
+and  meant  as  examples  of  various forms  of  DMS  input.  The x-y output
+data will appear as three lines of::
+
+    460769.27     5011648.45
+
+.. only:: man
+
+    Other programs
+    **************
+
+    The :program:`proj` program is limited to converting between geographic and
+    projected coordinates within one datum.
+
+    The :program:`cs2cs` program operates similarly, but allows translation
+    between any paor of definable coordinate reference systems, including
+    support for datum translation.
+
+    See also
+    ********
+
+    **cs2cs(1)**, **cct(1)**, **geod(1)**, **gie(1)**
+
+    Bugs
+    ****
+
+    A list of know bugs can be found at http://github.com/OSGeo/proj.4/issues
+    where new bug reports can be submitted to.
+
+    Home page
+    *********
+
+    http://proj4.org/