Hi, If you do not need to reproject or you are reprojecting just between KKJ zones you can live without towgs84 parameters. However, reprojecting to/from all the other systems will give an error of 150-200 meters. That is the thing that is not safe. Updating spatial_ref_sys is safe.
The most official parameters are in the JHS document http://docs.jhs-suositukset.fi/jhs-suositukset/JHS153/JHS153.pdf, table in page 10. Parameters seem to be the ones I have been using with Mapserver. I do not understand the mathematics myself but luckily it is not necessary. Just use correct parameters. -Jukka Rahkonen- Pena Kupen wrote: > Thank's Jukka, > On my spatial_ref_sys-table, there is proj4text like: +proj=tmerc +lat_0=0 +lon_0=27 +k=1.000000 +x_0=3500000 +y_0=0 +ellps=intl +units=m +no_defs So towgs84-parameter is missing. >> If it is not, update the record. >> > It this safe? Can it affect with unwanted result somewhere? >>You can read also >>http://latuviitta.org/documents/YKJ-TM35FIN_muunnos_ogr2ogr_cs2cs.txt (in >>Finnish, I suppose it is not a problem for you). >> > Yeps, language not, but understanding is something else ;-) > -Pena Rahkonen Jukka [jukka.rahko...@mmmtike.fi] kirjoitti: > Hi, > > I suppose that towgs84 parameters are missing. You can check this with psql: > > select proj4text from spatial_ref_sys where srid=2393; > > The result should be close to > +proj=tmerc +lat_0=0 +lon_0=27 +k=1.000000 +x_0=3500000 +y_0=0 +ellps=intl > +towgs84=-90.7,-106.1,-119.2,4.09,0.218,-1.05,1.37 +units=m +no_defs > If it is not, update the record. > > A related thing is that Mapserver epsg text file often comes without towgs84 > parameters for the Finnish KKJ zones. This is what I seem to have on this > computer: > KKJ / Finland Uniform Coordinate System > <2393> +proj=tmerc +lat_0=0 +lon_0=27 +k=1 +x_0=3500000 +y_0=0 +ellps=intl > +towgs84=-96.0617,-82.4278,-121.743,4.80107,0.34543,-1.37646,1.4964 +units=m > +no_defs <> > > You can see that the parameters are not the same. There are more parameter > sets around and that's actually the reason why Proj4 comes or at least used > to come without any parameters because none of the sets was authorized. The > results of these transformations are rather close and accurate to about one > meter. You can read also > http://latuviitta.org/documents/YKJ-TM35FIN_muunnos_ogr2ogr_cs2cs.txt (in > Finnish, I suppose it is not a problem for you). > > -Jukka Rahkonen- > > Pena Kupen wrote: > > > Hello all, > > > Last time I was successfully helped by Ralf - Thank's once more time! > http://postgis.refractions.net/pipermail/postgis-users/2011-March/029055.html > > > Now I have same type of problem, but I cannot get correct result. > > Table is: > CREATE TABLE location ( > location_id integer NOT NULL, > coord geometry > ); > > Data is in coord column as 2393 format. > > My sql is like: > select > y(location.coord) as y_ykj, > x(location.coord) as x_ykj, > y(ST_Transform(location.coord,4326)) as y_wgs84, > x(ST_Transform(location.coord,4326)) as x_wgs84 > from location where location_id = 'AAA123A' > > result for y_ykj and x_ykj are ok, but point of x_wgs84 and y_wgs84 are about > 180meters too much in east. > > -Pena > > -- Wippies-vallankumous on täällä! Varmista paikkasi vallankumouksen eturintamassa ja liity Wippiesiin heti! http://www.wippies.com/ _______________________________________________ mapserver-users mailing list mapserver-users@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/mapserver-users _______________________________________________ mapserver-users mailing list mapserver-users@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/mapserver-users
