NPE maps have always had major alignment problems which have seemed to me to be worse in the eastern side of the country. There's also a new problem, but I don't know whether it is in the JOSM WMS plugin, the tile server or what.
Consider three JOSM screenshots: http://www.frankieandshadow.com/xref/josm1.png http://www.frankieandshadow.com/xref/josm2.png http://www.frankieandshadow.com/xref/josm3.png The first is Landsat, obviously. It defaults with an offset of about 100m vertically and horizontally in my part of the world (52N 0E) as can be seen from the obvious course of the road on the satellite images at the orange arrows. But once the layer is aligned on known points, it tends to be aligned across the whole working area. NPE maps in contrast, in the second one, firstly has a relative displacement of tiles (about 150m) in JOSM which is obvious in this unadjusted download. (We also have to add to that that the map sheet boundaries don't line up anywhere near accurately) The third one though shows that even within a single tile, the alignment drifts extremely rapidly. I aligned the third one with the junction at point 1 near the top left of a tile, and you can see that at the bottom right of the tile, the bend I've marked is off by about 150m horizontally and 115m vertically over a distance of about 1500m - 10%. All the roads in this area are GPS surveyed (I did them). I mentioned this when NPE maps first arrived, but it's never been addressed. Is it a rectification problem, or a problem of how JOSM or the WMS plugin scales or displays the tiles? The tile displacement problem is recent and I'm sure that will easily be fixed. The variation across a tile is more awkward I think. David _______________________________________________ Talk-GB mailing list [email protected] http://lists.openstreetmap.org/listinfo/talk-gb
