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.TH "CCT" "1" "10 avril 2026" "9.8" "PROJ"
.SH NAME
cct \- Coordinate Conversion and Transformation
.SH SYNOPSIS
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\fBcct\fP [\fB\-cIostvz\fP [args]] \fI+opt[=arg]\fP ... file ...
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or
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\fBcct\fP [\fB\-cIostvz\fP [args]] {object_definition} file ...
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Where {object_definition}\ is one of the possibilities accepted
by \fBproj_create()\fP \%<#\:c\:.proj_create>, provided it expresses a coordinate operation
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.IP \(bu 2
a proj\-string,
.IP \(bu 2
a WKT string,
.IP \(bu 2
an object code (like \(dqEPSG:1671\(dq \(dqurn:ogc:def:coordinateOperation:EPSG::1671\(dq),
.IP \(bu 2
an object name. e.g. \(dqITRF2014 to ETRF2014 (1)\(dq. In that case as
uniqueness is not guaranteed, heuristics are applied to determine the appropriate best match.
.IP \(bu 2
a OGC URN combining references for concatenated operations
(e.g. \(dq\%<urn:ogc:def:coordinateOperation,coordinateOperation:EPSG::3895,coordinateOperation:EPSG::1618>\(dq)
.IP \(bu 2
a PROJJSON string. The jsonschema is at \%<https://\:proj\:.org/\:schemas/\:v0\:.4/\:projjson\:.schema\:.json>
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Added in version 8.0.0.

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\fBNote:\fP
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Before version 8.0.0 only proj\-strings could be used to instantiate
operations in cct\&.
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or
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\fBcct\fP [\fB\-cIostvz\fP [args]] {object_reference} file ...
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where {object_reference} is a filename preceded by the \(aq@\(aq character.  The
file referenced by the {object_reference} must contain a valid
{object_definition}.
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Added in version 8.0.0.

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.SH DESCRIPTION
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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.
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Note however that unlike the proj \%<#\:proj>, angular input must be in decimal degrees.
Any minutes and seconds given will be silently dropped.
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The following control parameters can appear in any order:
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.TP
.B \-c <x,y,z,t>
Specify input columns for (up to) 4 input parameters. Defaults to 1,2,3,4.
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.B \-d <n>
Added in version 5.2.0.

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Specify the number of decimals to round to in the output.
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.B \-I
Do the inverse transformation.
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.B \-o <output file name>, \-\-output=<output file name>
Specify the name of the output file.
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.B \-t <time>, \-\-time=<time>
Specify a fixed observation \fItime\fP to be used for all input data.
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.B \-z <height>, \-\-height=<height>
Specify a fixed observation \fIheight\fP to be used for all input data.
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.B \-s <n>, \-\-skip\-lines=<n>
Added in version 5.1.0.

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Skip the first \fIn\fP lines of input. This applies to any kind of input, whether
it comes from \fBSTDIN\fP, a file or interactive user input.
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.B \-v, \-\-verbose
Write non\-essential, but potentially useful, information to stderr.
Repeat for additional information (\fB\-vv\fP, \fB\-vvv\fP, etc.)
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.B \-\-version
Print version number.
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The \fI+opt\fP arguments are associated with coordinate operation parameters.
Usage varies with operation.
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cct is an acronym meaning \fICoordinate Conversion and Transformation\fP\&.
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The acronym refers to definitions given in the OGC 08\-015r2/ISO\-19111
standard \(dqGeographical Information \-\- Spatial Referencing by Coordinates\(dq,
which defines two different classes of \fIcoordinate operations\fP:
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\fICoordinate Conversions\fP, which are coordinate operations where input
and output datum are identical (e.g. conversion from geographical to
cartesian coordinates) and
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\fICoordinate Transformations\fP, which are coordinate operations where
input and output datums differ (e.g. change of reference frame).
.SH USE OF REMOTE GRIDS
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Added in version 7.0.0.

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If the \fBPROJ_NETWORK\fP \%<#\:envvar-PROJ_NETWORK> environment variable is set to \fBON\fP,
cct will attempt to use remote grids stored on CDN (Content
Delivery Network) storage, when they are not available locally.
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More details are available in the Network capabilities \%<#\:network> section.
.SH EXAMPLES
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.IP 1. 3
The operator specs describe the action to be performed by cct\&. So
the following script
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.EX
echo 12 55 0 0 | cct +proj=utm +zone=32 +ellps=GRS80
.EE
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will transform the input geographic coordinates into UTM zone 32 coordinates.
Hence, the command
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.EX
echo 12 55 | cct \-z0 \-t0 +proj=utm +zone=32 +ellps=GRS80
.EE
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Should give results comparable to the classic proj \%<#\:proj> command
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.EX
echo 12 55 | proj +proj=utm +zone=32 +ellps=GRS80
.EE
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.IP 2. 3
Convert geographical input to UTM zone 32 on the GRS80 ellipsoid:
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.EX
cct +proj=utm +ellps=GRS80 +zone=32
.EE
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.IP 3. 3
Roundtrip accuracy check for the case above:
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.EX
cct +proj=pipeline +ellps=GRS80 +zone=32 +step +proj=utm +step +proj=utm +inv
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.IP 4. 3
As (2) but specify input columns for longitude, latitude, height and time:
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.EX
cct \-c 5,2,1,4 +proj=utm +ellps=GRS80 +zone=32
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.IP 5. 3
As (2) but specify fixed height and time, hence needing only 2 cols in
input:
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.EX
cct \-t 0 \-z 0 +proj=utm +ellps=GRS80 +zone=32
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.IP 6. 3
Auxiliary data following the coordinate input is forwarded to the output
stream:
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.EX
$ echo 12 56 100 2018.0 auxiliary data | cct +proj=merc
1335833.8895   7522963.2411      100.0000     2018.0000 auxiliary data
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.IP 7. 3
Coordinate operation referenced through its code
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.EX
$ echo 3541657.3778 948984.2343 5201383.5231 2020.5 | cct EPSG:8366
3541657.9112    948983.7503  5201383.2482     2020.5000
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.IP 8. 3
Coordinate operation referenced through its name
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$ echo 3541657.3778 948984.2343 5201383.5231 2020.5 | cct \(dqITRF2014 to ETRF2014 (1)\(dq
3541657.9112    948983.7503  5201383.2482     2020.5000
.EE
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.SH BACKGROUND
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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.
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\fIcct\fP, 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.
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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.
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Hence, in honour of \fIcct\fP (the geodesist) this is cct (the program).
.SH SEE ALSO
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\fBproj(1)\fP, \fBcs2cs(1)\fP, \fBgeod(1)\fP, \fBgie(1)\fP, \fBprojinfo(1)\fP, \fBprojsync(1)\fP
.SH BUGS
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A list of known bugs can be found at \%<https://\:github\:.com/\:OSGeo/\:PROJ/\:issues>
where new bug reports can be submitted to.
.SH HOME PAGE
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\%<https://\:proj\:.org/>
.SH Author
Thomas Knudsen
.SH Copyright
1983-2026, PROJ contributors
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