CCT(1)                               PROJ                               CCT(1)

NAME
       cct - Coordinate Conversion and Transformation

SYNOPSIS
          cct [-cIostvz [args]] +opt[=arg] ... file ...

       or
          cct [-cIostvz [args]] {object_definition} file ...

       Where {object_definition} is one of the possibilities accepted by
       proj_create() <#c.proj_create>, provided it expresses a coordinate
       operation

          o a proj-string,

          o a WKT string,

          o an object code (like "EPSG:1671"
            "urn:ogc:def:coordinateOperation:EPSG::1671"),

          o an object name. e.g. "ITRF2014 to ETRF2014 (1)". In that case as
            uniqueness is not guaranteed, heuristics are applied to determine
            the appropriate best match.

          o a OGC URN combining references for concatenated operations (e.g.
            "<urn:ogc:def:coordinateOperation,coordinateOperation:EPSG::3895,coordinateOperation:EPSG::1618>")

          o a PROJJSON string. The jsonschema is at <https://proj.org/schemas/
            v0.4/projjson.schema.json>

          Added in version 8.0.0.


          Note:
             Before version 8.0.0 only proj-strings could be used to
             instantiate operations in cct.

       or
          cct [-cIostvz [args]] {object_reference} file ...

       where {object_reference} is a filename preceded by the '@' character.
       The file referenced by the {object_reference} must contain a valid
       {object_definition}.
          Added in version 8.0.0.


DESCRIPTION
       cct is a 4D equivalent to the proj <#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.

       Note however that unlike the proj <#proj>, angular input must be in
       decimal degrees.  Any minutes and seconds given will be silently
       dropped.

       The following control parameters can appear in any order:

       -c <x,y,z,t>
              Specify input columns for (up to) 4 input parameters. Defaults
              to 1,2,3,4.

       -d <n> Added in version 5.2.0.


              Specify the number of decimals to round to in the output.

       -I     Do the inverse transformation.

       -o <output file name>, --output=<output file name>
              Specify the name of the output file.

       -t <time>, --time=<time>
              Specify a fixed observation time to be used for all input data.

       -z <height>, --height=<height>
              Specify a fixed observation height to be used for all input
              data.

       -s <n>, --skip-lines=<n>
              Added in version 5.1.0.


              Skip the first n lines of input. This applies to any kind of
              input, whether it comes from STDIN, a file or interactive user
              input.

       -v, --verbose
              Write non-essential, but potentially useful, information to
              stderr.  Repeat for additional information (-vv, -vvv, etc.)

       --version
              Print version number.

       The +opt arguments are associated with coordinate operation parameters.
       Usage varies with operation.

       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).

USE OF REMOTE GRIDS
       Added in version 7.0.0.


       If the PROJ_NETWORK <#envvar-PROJ_NETWORK> environment variable is set
       to ON, cct will attempt to use remote grids stored on CDN (Content
       Delivery Network) storage, when they are not available locally.

       More details are available in the Network capabilities <#network>
       section.

EXAMPLES

       1. The operator specs describe the action to be performed by cct. So
          the following script

          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

          echo 12 55 | cct -z0 -t0 +proj=utm +zone=32 +ellps=GRS80

       Should give results comparable to the classic proj <#proj> command

          echo 12 55 | proj +proj=utm +zone=32 +ellps=GRS80

       2. Convert geographical input to UTM zone 32 on the GRS80 ellipsoid:

          cct +proj=utm +ellps=GRS80 +zone=32

       3. Roundtrip accuracy check for the case above:

          cct +proj=pipeline +ellps=GRS80 +zone=32 +step +proj=utm +step +proj=utm +inv

       4. As (2) but specify input columns for longitude, latitude, height and
          time:

          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:

          cct -t 0 -z 0 +proj=utm +ellps=GRS80 +zone=32

       6. Auxiliary data following the coordinate input is forwarded to the
          output stream:

          $ echo 12 56 100 2018.0 auxiliary data | cct +proj=merc
          1335833.8895   7522963.2411      100.0000     2018.0000 auxiliary data

       7. Coordinate operation referenced through its code

          $ echo 3541657.3778 948984.2343 5201383.5231 2020.5 | cct EPSG:8366
          3541657.9112    948983.7503  5201383.2482     2020.5000

       8. Coordinate operation referenced through its name

          $ echo 3541657.3778 948984.2343 5201383.5231 2020.5 | cct "ITRF2014 to ETRF2014 (1)"
          3541657.9112    948983.7503  5201383.2482     2020.5000

BACKGROUND
       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 cct (the program).

SEE ALSO
       proj(1), cs2cs(1), geod(1), gie(1), projinfo(1), projsync(1)

BUGS
       A list of known bugs can be found at <https://github.com/OSGeo/PROJ/
       issues> where new bug reports can be submitted to.

HOME PAGE
       <https://proj.org/>

Author
       Thomas Knudsen

Copyright
       1983-2026, PROJ contributors

9.8                              10 avril 2026                          CCT(1)