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(), 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 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, 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 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 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 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
1983-2025, PROJ contributors
9.6 08 Sep 2025 cct(1)
proj 9.7.0 - Generated Thu Oct 16 18:16:47 CDT 2025