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.
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.
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.
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>
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.
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)
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
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
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.
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) |
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 |
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 |
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 |
Descriptions of the grids available in the NordicTransformations repository.
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.
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.
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.
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.
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.