[OSM-talk] Freemap-NPE: OSM + New Popular Edition Mashup

[Nick Whitelegg]

>>These paths to the North East of Reading should lie either side of the
>>River Thames, but instead one seems to be in the river and the other 
some
>>distance away from it. Which layer needs budging over here? The OSM data
>>should be accurate given that I cycled down each path, twice per side.
>

>I think the problem is with the rectification of the npe mapping. I found
>for a sheet I wanted to do a gpx trace over that the calibration error 
was
>83m in one direction. You can see basically the same issue on the link 
you
>gave in that you can see the gridline on the far right tiles are a little
>way inside the edge of the display area. Zoom right in and you will find 
the
>left right shift error matches very well with the error seen at your two
>footpaths.

That seems to be the case in my experience too. In the default area 
(Fernhurst, Sussex) the paths seem to be exactly where they should be. In 
some places in Cheshire, they're slightly off.

I wonder if it would be possible to take the rectification shifts gathered 
from the GPX tracing application and store them in a database, so that the 
corrections could be applied per sheet?

Nick