Selon Andrew Chapman <[email protected]>: > I've been asked to look into a problem where our exported shapefiles are > being displaced approximately 5.7m SSW from their true position. > > Everything works as expected up to and including 1.7.4, but 1.8.0 and Master > demonstrate the problem. KML files are ok as are shapefiles using other CRSs > (e.g. EPSG:3857 - WGS 84 / Pseudo Mercator). If, using 1.8.0, I save a > EPSG:27700 layer as a shapefile with a different CRS or as a KML file, the > displacement is exported and loads as such in earlier versions of QGIS or > external applications (Google Earth, ArcGIS). > > In 1.7.4 the layer metadata shows > +proj=tmerc +lat_0=49 +lon_0=-2 +k=0.9996012717 +x_0=400000 +y_0=-100000 > +ellps=airy > +towgs84=446.448,-125.157,542.06,0.15,0.247,0.842,-20.489 +units=m > +no_defs > > while in 1.8.0 it shows > +proj=tmerc +lat_0=49 +lon_0=-2 +k=0.9996012717 +x_0=400000 +y_0=-100000 > +ellps=airy > +towgs84=375,-111,431,0,0,0,0 +units=m +no_defs > > The '+towgs84' parameters have changed. > > For anyone primarily using OSGB shapefiles (e.g. the approximately 10,000 UK > town and parish councils who could use free Ordnance survey maps and QGIS) > this leads to a major creditability problem if we wish to share data with > other organisations. > > Has anyone else seen this problem?
There's a GDAL ticket about that : http://trac.osgeo.org/gdal/ticket/4597 Frank, I've attached in it a libgeotiff patch that should solve this by defining an override. _______________________________________________ Qgis-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/qgis-user
