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PROJ parameters for transformations defined by the Nordic Geodetic Commision

The Nordic Geodetic Commision (NKG) defines transformations betweeen the national realisations of the ETRS89 and the various realisations of the global reference system ITRS. This repository is a collection of transformation parameters and gridded deformation models that can be used with the transformation software PROJ.

License

All files in this repository are licensed under the Creative Commons Attribution 4.0 license, or as it is commonly referred to, CC-BY 4.0. The license allows redistribution and modification of the files as long as the original rights holder is credited. In this case the proper rights holder to credit is either NKG or one of the individual members of NKG, typically the local National Mapping Authority that has the jurisdiction in the country for which the file is related to. For the Danish geoid grid the proper attribution is therefore "Agency for Data Supply and Efficiency". Below the correct authority to attribute for a given files is specified.

License: CC BY 4.0

Concept

All NKG-transformations are defined such that the common Nordic reference frame, NKG_ETRF00, functions as a transformation hub. That is, all transformations from e.g. ITRFxx to the national realisations of ERTS89 go through NKG_ETRF00. We use this to our advantage when setting up the parameter files for PROJ. By leveraging init-files in PROJ a system is set up that delivers an easy-to-use shorthand notation for day to day use of PROJ.4 that hides most of the complexity of the transformations for the user.

In addition to using the common Nordic frame as a hub datum for transformations across national border, we use the national realisations of ERTS89 as hub datums within those countries. That is, transformations between local coordinate reference systems always go through the local realisation of ETRS89. This concept of having a common Nordic hub datum and a set of national hub datums enables us to perform a wide range of transformations between various local and Nordic systems, without having to define transformation parameters for all of the possible paths between systems.

Usage in PROJ

It is out of the scope of this collection of grids and parameter files to also describe all the nitty details of the usage of PROJ but a short introduction is warranted nonetheless. We refer to the PROJ documentation for specific details. It is also worth noting that the project's mailing list is a valuable resource for the PROJ user. Use it when you have questions you can't find answers to in the documentation.

All of the transformation setups in the sections below can be used with the cct application, e.g.

cct +proj=... <file>

For coordinates without an epoch the -t option of cct can be used, e.g.

cct -t 2015.830 +proj=... <file>

Consult the documentation for cct for further details on the use of cct. cct is the go-to application for spatio-temporal (4D) coordinates.

All transformation setups using cct are describing the transformation between two systems. An example of such transformation is given below where we transform Danish UTM32 coordinates to System34 with cct:

cct +proj=pipeline +step +init=DK:UTM32 +inv +step +init=DK:S34S <file>

Transforming coordinates

In the following examples of various transformations are given in the form of PROJ proj-strings. See the above section for a few examples of how the can be used. Consult the PROJ documentation for further details and examples.

Global reference frames and the common Nordic frame

Below is a few examples of proj-strings that is used for the NKG-transformations.

NKG_ETRF00 (the common NKG reference frame) to ITRF2014:

+init=NKG:ITRF2014

ITRF2014 to the Danish realisation of ETRS89:

+proj=pipeline
  +step +init=NKG:ITRF2014 +inv  # ITRF2014 -> NKG_ETRF00 (observation epoch given in coordinate input)
  +step +init=NKG:DK             # NKG_ERTF00 -> ETRS89(DK)

National coordinate reference systems

When coordinates relate to the common Nordic frame it is possible to transform them to the various national coordinate reference systems.

For instance a transformation between the Danish systems System34 Jylland and UTM32/ETRS89+DVR90 is performed with:

+proj=pipeline
  +step +init=DK:S34J +inv      # System34 Jylland -> ETRS89(DK)
  +step +init=DK:UTM32N_DVR90   # ETRS89(DK) -> ETRS89(DK) / UTM Zone 32

Below is an example of transforming coordinates from the common Nordic frame to the Danish compound system of UTM32 and the local vertical reference, DVR90:

+proj=pipeline
  +step +init=NKG:DK            # NKG_ETRF00 -> ETRS89(DK)
  +step +init=DK:UTM32N_DVR90   # ETRS89(DK) -> ETRS89(DK)/UTM Zone 32

Transforming between coordinate reference systems across national borders is also possible. Here Swedish UTM coordinates are transformed to Norwegian UTM coordinates, both of course referenced to the local realisations of ETRS89:

+proj=pipeline
  +step +init=SE:UTM32N +inv    # ETRS89(SE)/UTM Zon32 -> ETRS89(SE)
  +step +init=NKG:SE +inv       # ETRS89(SE) -> NKG_ETRF00
  +step +init=NKG:NO            # NKG_ETRF00 -> ETRS89(NO)
  +step +init=NO:UTM32N         # ETRS89(NO) -> ETRS89(NO)/UTM Zone 32

From global frame to local coordinate reference system

Transforming coordinates from a global frame to a local coordinate reference system involved two hub datums. First the common Nordic frame and second one of the national realisations of ERTS89. For instance, ITRF2014-coordinates from a GNSS-station in Denmark can be transformed to a local UTM-coordinates with:

+proj=pipeline
  +step +init=NKG:ITRF2014 +inv  # ITRF2014 -> NKG_ETRF00
  +step +init=NKG:DK             # NKG_ETRF00 -> ETRS89(DK)
  +step +init=DK:UTM32N          # ETRS89(DK) -> ETRS89(DK)/UTM Zone 32

"Installing" the PROJ resource files

PROJ looks for resource files in a few standard locations as well as a user specified libarary, that can be controlled with the environment variable PROJ_LIB. On Windows systems PROJ only looks for resource files in the folder specified in PROJ_LIB and the current directory. On UNIX(-like) systems PROJ also looks in /usr/local/share/proj. With this in mind, the NKG PROJ resource files should be copied to one of those locations.

Most Windows-users will probably be using the OSGeo4W distribution of PROJ, which usually has PROJ_LIB set to C:\OSGeo4W64\share\proj.

Parameter files

NKG

Attribution: The Nordic Geodetic Commision.

Transformation parameters for transformations going to and from the common Nordic frame NKG_ETRF00. Includes transformations to and from global frames such as ITRFxx and the national realisations of ETRS89.

At the moment the NKG file is not yet created, but eventually the following transformation entries can be used in conjunction with the NKG parameter file:

Entry Description
ITRF2000
ITRF2005
ITRF2008
ITRF2014
DK Danish realisation of ETRS89 (ETRF92@1994.704)
EE Estonian realisation of ETRS89 (ETRF96@1997.56)
FO Faroese realisation of ETRS89 (ETRF2000@2008.75)
FI Finish realisation of ETRS89 (ETRF96@1997.0)
LV Latvian realisation of ETRS89 (ETRF89@1992.75)
LT Lithuanian realisation of ETRS89 (ETRF2000@2003.75)
NO Norwegian realisation of ETRS89 (ETRF93@1995.0)
SE Swedish realisation of ETRS89 (ETRF97@1999.5)

DK

Attribution: Agency for Data Supply and Efficiency.

Entry Description
S34J System34 Jylland
S34S System34 Sjælland
S45B System45 Bornholm
KP2000J KP2000 Jylland
KP2000J_DVR90 KP2000 Jylland + DVR90 heights
KP2000J_DNN KP2000 Jylland + DNN heights
KP2000S KP2000 Sjælland
KP2000S_DVR90 KP2000 Sjælland + DVR90 heights
KP2000S_DNN KP2000 Sjælland + DNN heights
KP2000B KP2000 Bornholm
KP2000B_DVR90 KP2000 Bornholm + DVR90 heights
KP2000B_DNN KP2000 Bornholm + DNN heights
DKTM1 DKTM1
DKTM1_DVR90 DKTM1 + DVR90 heights
DKTM1_DNN DKTM1 + DNN heights
DKTM2 DKTM2
DKTM2_DVR90 DKTM2 + DVR90 heights
DKTM2_DNN DKTM2 + DNN heights
DKTM3 DKTM3
DKTM3_DVR90 DKTM3 + DVR90 heights
DKTM3_DNN DKTM3 + DNN heights
DKTM4 DKTM4
DKTM4_DVR90 DKTM4 + DVR90 heights
DKTM4_DNN DKTM4 + DNN heights
UTM32N UTM Zone 32N
UTM32N_DVR90 UTM Zone 32N + DVR90 heights
UTM32N_DNN UTM Zone 32N + DNN heights
UTM33N UTM Zone 33N
UTM33N_DVR90 UTM Zone 33N + DVR90 heights
UTM33N_DNN UTM Zone 33N + DNN heights
DVR90 Danish Vertical Reference of 1990
DNN Dansk Normal Nul

FO

Attribution: Agency for Data Supply and Efficiency.

Entry Description
FOTM FOTM
FOTM_FVR09 FOTM + FVR09 heights
UTM29N UTM Zone 29N
UTM29N_FVR09 UTM Zone 29N + FVR09 heights
FD54 Faroese Datum of 1954
FK89  
FVR09 Faroese Vertical Reference of 2009

GL

Attribution: Agency for Data Supply and Efficiency.

Definitions of Greenlandic systems. Uses GR96 as pivot datum.

Entry Description
ITRF2014 Transformation from GR96 to ITRF2014
ITRF2008 Transformation from GR96 to ITRF2008
GVR2000 Greenlandic Vertical Reference of 2000
GVR2016 Greenlandic Vertical Reference of 2016
UTM18N UTM Zone 18N
UTM18N_GVR2000 UTM Zone 18N + GVR2000 heights
UTM18N_GVR2016 UTM Zone 18N + GVR2016 heights
UTM19N UTM Zone 19N
UTM19N_GVR2000 UTM Zone 19N + GVR2000 heights
UTM19N_GVR2016 UTM Zone 19N + GVR2016 heights
UTM20N UTM Zone 20N
UTM20N_GVR2000 UTM Zone 20N + GVR2000 heights
UTM20N_GVR2016 UTM Zone 20N + GVR2016 heights
UTM21N UTM Zone 21N
UTM21N_GVR2000 UTM Zone 21N + GVR2000 heights
UTM21N_GVR2016 UTM Zone 21N + GVR2016 heights
UTM22N UTM Zone 22N
UTM22N_GVR2000 UTM Zone 22N + GVR2000 heights
UTM22N_GVR2016 UTM Zone 22N + GVR2016 heights
UTM23N UTM Zone 23N
UTM23N_GVR2000 UTM Zone 23N + GVR2000 heights
UTM23N_GVR2016 UTM Zone 23N + GVR2016 heights
UTM24N UTM Zone 24N
UTM24N_GVR2000 UTM Zone 24N + GVR2000 heights
UTM24N_GVR2016 UTM Zone 24N + GVR2016 heights
UTM25N UTM Zone 25N
UTM25N_GVR2000 UTM Zone 25N + GVR2000 heights
UTM25N_GVR2016 UTM Zone 25N + GVR2016 heights
UTM26N UTM Zone 26N
UTM26N_GVR2000 UTM Zone 26N + GVR2000 heights
UTM26N_GVR2016 UTM Zone 26N + GVR2016 heights
UTM27N UTM Zone 27N
UTM27N_GVR2000 UTM Zone 27N + GVR2000 heights
UTM27N_GVR2016 UTM Zone 27N + GVR2016 heights
UTM28N UTM Zone 28N
UTM28N_GVR2000 UTM Zone 28N + GVR2000 heights
UTM28N_GVR2016 UTM Zone 28N + GVR2016 heights
UTM28N UTM Zone 29N
UTM29N_GVR2000 UTM Zone 29N + GVR2000 heights
UTM29N_GVR2016 UTM Zone 29N + GVR2016 heights

Grids

Descriptions of the grids available in the NordicTransformations repository.

nkgrf03vel_realigned_xy.ct2

Attribution: The Nordic Geodetic Commision.

The horizontal component of the readjusted NKG velocity model from 2003. The readjustment is performed as described in Häkli et al. (2016) The velocity model is used in transformations going from global reference frames to the individual national realizations of ETRS89.

nkgrf03vel_realigned_z.gtx

Attribution: The Nordic Geodetic Commision.

The vertical component of the readjusted NKG velocity model from 2003. The readjustment is performed as described in Häkli et al. (2016) The velocity model is used in transformations going from global reference frames to the individual national realizations of ETRS89.

dvr90.gtx

Attribution: Agency for Data Supply and Efficiency.

Geoid model for the Danish height reference DVR90. The grid implements the transformation between GRS80 ellipsoid heights and heights in the DVR90 system. Grid coordinates are referenced to ETRS89.

fvr09.gtx

Attribution: Agency for Data Supply and Efficiency.

Geoid model for the Faroese height reference FVR09. The grid implements the transformation between GRS80 ellipsoid heights and heights in the FVR09 system. Grid coordinates are referenced to ETRS89.

gvr2016.gtx

Attribution: Agency for Data Supply and Efficiency.

Geoid model for the Greenlandic height reference GVR2016. The grid implements the transformation between GRS80 ellipsoid heights and heights in the GVR2016 system. Grid coordinates are referenced to GR96.

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PROJ init-files describing the nordic transformations

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