OpenStreetMap
Re-drew sections of the A27 along the South Coast which I can see via Yahoo tiles as it seems to be out by about 15-20'.
However, there are large sections that I can't see due to lack of low-level mapping or clouds. So, if there's anyone along the South Coase available to go over the route with a GPS, you'd probably be able to correct it all fairly easily
Cheers
Mike
Kaozeadenn
Evezhiadenn a-berzh njd27 d'an 22 August 2008 da 10:14
For what it's worth if the aerial mapping is out by 15-20' then it's likely to be the aerial mapping which is aligned badly - particularly in areas where there aren't many features. If you view all the GPS tracks for the road and take an average that is far more accurate generally.
Evezhiadenn a-berzh LivingWithDragons d'an 22 August 2008 da 14:51
It's probably been done with a GPS and, as njd27 says, the aerial photography out.
Also not everyone uploads their GPS tracks, some people just open them locally in JOSM.