Hi Roger, I am not sure what you mean by "Sweref99_tm Cartesian values", but I think you mean SWEREF99 geocentric cartesian coordinates (with respect to the centre of the earth and the Z-axis in line with the rotation axis and X-axis through Greenwich). If so you can use the following command:
echo 21 69 0.000 2022.0 | cct +proj=cart +ellps=GRS80 which gives : 2140155.9896 821528.9138 5931972.9199 2022.0000 Note that cct is used instead of proj, and then you need also to give an epoch. In this case when just transforming between lat long ellh to X Y Z , it does not matter which epoch you give. But in case you transform from or to a dynamic reference system like ITRF then this epoch is important. Usually you give the epoch of the measurement. You can also use the EPSG-codes if you prefer: echo 69 21 0.000 | cs2cs EPSG:4326 EPSG:4976 with the result: 2140155.99 821528.91 5931972.92 Note that the input latitude and longitude are in different order than for proj and cct! or use the code for WGS84 (which has the zero-transformation to SWEREF99 in EPSG): echo 69 21 0.000 | cs2cs EPSG:4326 EPSG:4976 2140155.99 821528.91 5931972.92 In many case you can consider SWEREF99=ETRS89=WGS84, which also is done with the transformation in the EPSG-database. This approximation is OK if you can accept an error up to 1 m. In case you need an accurate transformation (sub-cm) from ITRF2014/WGS84 to SWEREF 99 ( in geocentric cartesian coordinates) you can use the NKG:ITRF2014_TO_SE (implemented in PROJ from version 7.2.1): echo 2140155.9896 821528.9138 5931972.9199 2022.0000| cct NKG:ITRF2014_TO_SE 2140156.5941 821528.5956 5931972.5885 2022.0000 Hope it helps! Best Regards, Lotti Jivall Geodesist LANTMÄTERIET EMAIL lotti.jiv...@lm.se TELEPHONE 026-63 37 40 MOBILE 072-222 56 14 ADDRESS Lantmäteriet, Geodetisk infrastruktur, 801 82 Gävle WEBB www.lantmateriet.se www.linkedin.com/company/lantmateriet www.facebook.com/lantmateriet www.instagram.com/lantmateriet -----Ursprungligt meddelande----- Från: PROJ <proj-boun...@lists.osgeo.org> För Roger Oberholtzer Skickat: den 20 april 2022 15:24 Till: PROJ <PROJ@lists.osgeo.org> Ämne: [PROJ] Sweref99 Cartesian We have been using proj to get Sweref99_tm (EPSG:3006) from WGS84 (EPSG:4326) values we collect from a GPS receiver. All is working great. We have had a request to provide Sweref99_tm Cartesian values. I have looked at https://proj.org/operations/conversions/cart.html#cart but I'm unclear how to do this in the context of Sweref99_tm. If I don't use the EPSG codes, I get the expected Sweref99_tm values with: proj +proj=tmerc +ellps=GRS80 +k=0.9996 +x_0=500000 +y_0=0 +lon_0=15.0 +lat_0=0.0 Would it just be changing +proj=tmerc to +proj=cart ? I get values. But I don't know if they are correct. echo 21.0000000000 69.0000000000 0.000 | proj +proj=tmerc +ellps=GRS80 +k=0.9996 +x_0=500000 +y_0=0 +lon_0=15.0 +lat_0=0.0 739639.19 7666089.70 0.000 echo 21.0000000000 69.0000000000 0.000 | proj +proj=cart +ellps=GRS80 +k=0.9996 +x_0=500000 +y_0=0 +lon_0=15.0 +lat_0=0.0 2279859.27 239622.87 0.000 Also, can this be done when specifying the EPSG:3006 code directly? -- Roger Oberholtzer _______________________________________________ PROJ mailing list PROJ@lists.osgeo.org https://lists.osgeo.org/mailman/listinfo/proj _______________________________________________ PROJ mailing list PROJ@lists.osgeo.org https://lists.osgeo.org/mailman/listinfo/proj
