So.. my two cents on the topic on European CRS. I can recommend this site that also should have some parameters for the different countries:
http://crs.bkg.bund.de/crs-eu/ On the question with the warping tool. Of course, one could calculate the BW paramters. But the problem is that this would require to my knowledge height information on the poins (i.e. the height from the Geoid) as the BW is done between two 3D geocentric coordinate systems (Michael may correct me here). I would agree that just using the warping tool (it is actually some kind of rubber-sheet transform) is probably the better/easier choice if one has points surrounding(!!!) the area of interest. finally: I am not sure if Germany uses grid approaches to get the needed accuracy. As far as I know we have different parameters for the German countries (and on the website above parameters for north, mid and south). But this problem occurs only for GIS/GPS transformations. Surveying data are correctly measured in local coordinate systems using reference points (triangulaton networks) and differential GPS reference service stations (SAPOS). But I must admit, that my knowledge on this is not up to date since 5 years. However, what I know from Finland is that they do not use a grid method but apply after the transformation + projection a plane Helmert/Affine transformation to minimize the errors towards the old KKJ system. The Swiss actually documented their efforts quite well too. And I think they use a grid approach too (but I would need to check that). so far on my 5 year old knowledge @Michael: If I can help ... I will try to :) Stefan Giuseppe Aruta wrote: > Hi all, > working around Edgar Soldin's Coordinate transformation plugin I finally > reached the (un)-famous problem of setting Bursa-Wolf parameters (BW) > for the tranformation between different datum/projections. > I realize that the problem is not so simple as it is shows: > 1) despite the EPSG official archive on net > (http://www.epsg-registry.org/) and other informations, there is no > unique BW parameters even between the same transformation. > For instance, searching on EPSG register, EPSG1660 (transformation > from Italian ROMA40 to WGS84) I had the official parameters for Italy > mainland with a maximum error of 4 metres. > Well, I tested these parameters in some places "mainland" in Italy, I > had an errror even of 60 metres, for instance, in Southern Italy > More than this I discover that some regions/areas defined their own > parameters. > This happens becaue the transformation between ROMA40, ED50 e WGS84 is > not correlated by geometric relations or simple math but by > comparing coordinates of some points within different . > > > The resault is this: > > Edgar's plugin works fine but people need to know the BW parameters for > the area of their interest. And sometimes this is not easy to do..... > (in respect to EPSG, geotools, etc). I image this is a common problem in > Europe > > ************************************************************ > > I will go anyway to write the tutorial page about projections on wiki > since this could be useful for who is interested. I will also put on > wiki some modified cs.conf (configurations) files optrimized for local > transformation (Umbria-Tuscany, South Tyrol and Campania-Basilicata). > Note that there is no problem with transformation between crs that don't > BW parameters (eg. WGS84 to WGS84/UTM..) to be used for GPS fanatics! > > ********************************************************** > The bulk of my letter is the follow notes: > Since OpenJUMP has some warping tools (Warp and even New affine > transformation). Is it possible to calculate local Bursa-Wolf parameters > using these tools on some reference points? Does somebody thought about > before? > This probabily could be an interesting area of research (for pratical > usage) of OpenJUMP: A way or a plugin that calculate local Bursa Wolf > parameters. > > I pass these questions expecially to Europian collugues since this maybe > is acommon pronblem: Gauss (Kruge, Boaga, etc) vs WGS84 or ETRS89 > > *************************************** > > Regards and thanks for the answers > > Peppe > > > ------------------------------------------------------------------------ > Tante idee per la salvaguardia del pianeta su > Yahoo! for good > <http://us.rd.yahoo.com/mailuk/taglines/isp/control/*http://us.rd.yahoo.com/evt=52436/*http://it.promotions.yahoo.com/forgood/environment.html>. > > > > > ------------------------------------------------------------------------ > > ------------------------------------------------------------------------- > This SF.net email is sponsored by the 2008 JavaOne(SM) Conference > Don't miss this year's exciting event. 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