ITRF2014 to SWEREF 99 Transformation

[AliciaSullivan]

Hey all, I am working with a Swedish customer and they brought up that the ITRF2014 and SWEREF 99 transformation is not implemented yet in PROJ. Has this transformation been implemented in ArcGIS?

[BojanŠavrič]

No direct transformation to ITRF 2014 has been implemented in ArcGIS. We currently support three transformations related to SWEREF99, SWEREF99 to ETRS 1989, SWEREF99 to WGS 1984, and SWEREF99 to RT90. All three are the ones registered with EPSG.
Does your customer has any official documentation about this transformation?

[AliciaSullivan]

Hi Bojan,

Ok thanks very much for the information. The specification they referenced are as follows from the Lantmäteriet was the following: 

The above mentioned transformations (both the accurate NKG transformation with a velocity
model and the simplified 7-parameter trasformations) go to and from cartesian XYZ coordinates:
XYZ(ITRF14) -> XYZ(SW99). You have to add the following two transformations to end up in
SWEREF 99 1200:
a. XYZ(SW99) -> Lat Long Ellh (SW99). Formulas from cartesian to geodetic coordintes
could e.g. be found here https://www.lantmateriet.se/en/maps-and-geographic-
information/gps-geodesi-och-swepos/Om-
geodesi/Transformationer/Transformationsmetoder/?faq=4216
b. Lat Long Ellh (SW99)-> SWEREF 99 1200. Formulas for the Transversal map projection is
found here https://www.lantmateriet.se/globalassets/kartor-och-geografisk-
information/gps-och-geodetisk-matning/gauss_conformal_projection.pdf and the
parameters for the local SWEREF 99 zones here: https://www.lantmateriet.se/en/maps-
and-geographic-information/gps-geodesi-och-
swepos/Referenssystem/Tvadimensionella-system/SWEREF-99-projektioner/
The simplifioed transformation is on the 2-3 cm level when using the parameters for each year.

[MelitaKennedy]

Hi Alicia, 

I found a transformation in a pdf but it looks like it converts between ITRF2005 @2003.75 to SWEREF99. The parameters are:

TX = 0.033750

TY = 0.029875

TZ = -0.080450

D [ppb] = 0.78 

RX [0.001”] =  -2.134

RY [0.001”] = -7.765

RZ [0.001”] = 9.810

and using the coordinate frame method. There's another pdf file that discussion transformations between ITRF2014 and various other frames. It looks like Table 4 has the values to convert between ITRF2014 and SWEREF99, at least for southern Sweden. Because the document states that it's for maritime applications, the transformation may really be good for offshore areas only.

Melita