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

[David Sheldon]

On Mon, Oct 30, 2006 at 12:28:46PM -0000, Andy Robinson wrote:
> 
> Or better still have users able to calibrate individual grid boxes (as per
> the gpx tracing stuff) and use that to collect rectification information.
> Since I assume that the error occurs within the sheet and that the edges of
> the sheet are presumably correct.

Sadly not. As the scans were not rectangular we cropped bits off the
maps, sometimes 100yds was cropped from the bottom or right so if you do
this you will end up with gaps. 

Our aim was to create something good enough to collect postcode
locations in a reasonable time. It took under a week to do what we did,
it would have taken significantly longer to write code to detect all the
corners of the maps and warp the resuts (even using gdal).

If a group of people want to work on improving the tiles I think we can
make the scans available under the CC-NC licence for you to work on and
improve the results.

An example map is available at:
http://ustile.npemap.org.uk/example_maps/158_oxford_and_newbury.jpg 

The input to the tiling program is a 5000x5625 jpeg, with the grid lines
125px apart. Our version is at 
http://ustile.npemap.org.uk/example_maps/sheet-158.jpg

This is actually a very good example. If someone finds a badly tiled
area I can put up these two files for that area, and people can try to
improve it.

David
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