> > I get a much better alignment for that area with the re-rectified > NPE tiles > > from TimSC's space at http://dev.openstreetmap.org/~timsc/wms2/map.php? > Yes, indeed, vastly better (and the images are clearer too, and the > tiles braking up problem isn't there). Even if I pan several tens of > km it is still in sync, and it seems to be in sync from the download > - no initial adjustment needed.
I rectified the NPE images available in Potlatch (and later republished via Tim's WMS for those of you using inferior editors ;) ) with 90 control points per sheet. It took bloody ages! But it does mean they're very, very close to the originals. The original NPE images found at www.npemap.org.uk, and on the older WMS, had only been rectified with some rough whole-sheet rotation and shearing operations in Photoshop or similar. These were in fact rectified for postcode input at npemap.org.uk, where the accuracy was less critical. Personally I'm a bit tired of fixing JOSM users' crappy tracings and would like the old WMS to be removed! But the fact that even the Potlatch 90-point NPE tiles need a little manual correction to GPS (space-drag in Potlatch) tells you something about the OS's surveying accuracy back then. As the 7th series followed straight on from NPE with no major resurvey at first, you should expect there still to be some displacement. cheers Richard _______________________________________________ Talk-GB mailing list [email protected] http://lists.openstreetmap.org/listinfo/talk-gb
