2011/1/22 Hanno Hecker <vetinari+...@ankh-morp.org>: > Hmm, either I've an error, or the coordinates from these are ~130m > off from what we have in OSM... > I've used EPSG:3021 (== RT90 2.5 gon V) to convert these into useable
It's been a while since I looked into this, but I remember that conversion WGS84 <-> RT90 is tricky because of the different geodetic datums. I believe that the method actually recommended by Lantmäteriverket is to fake the calculation by fudging the parameters in the Gauss-Krüger formula (http://www.lantmateriet.se/templates/LMV_Page.aspx?id=5197). Somewhere on their web site (I can't find it now; I can never find anything on their web when I need it...) I also found parameters for an approximate "six-parameter transform" which I translated into proj4 syntax as follows (this is from WGS84 to RT90): cs2cs +proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs +to +proj=tmerc +lat_0=0 +lon_0=15.80827777777778 +k=1 +x_0=1500000 +y_0=0 +ellps=bessel +units=m +no_defs +towgs84=414.1055,41.3265,603.0582,-.8551,2.1413,-7.0227,0 I believe it worked decently when I tried it, but I have forgotten all about how I came up with those numbers at the end... -- Ture _______________________________________________ Talk-se mailing list Talk-se@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-se