OpenStreetMap
Today I spent a couple of hours wandering around on a beautiful day, with nearly a hundred waypoints recorded , using both audio and photo.
Then of course I come home to JOSM, load my data and find that nothing lines up to the current data. How are you supposed to know how accurate the previous data is?
I try to add an accuracy tag to my data, so at least if I go out again and get a better accuracy I can replace my nodes.
Pity not everyone does, it could make life alot easier.
Discussion
Comment from andygates on 15 August 2010 at 22:22
If the old data is from NPE maps (source=NPE, or obvious big jaggy lines), it's a fair bet that it is shifted relative to the real world - NPE maps were large-scale and the geo-line-up-ness is often off by tens of metres. Good GPS data is better (and usually lines up near-perfectly with the Ordnance Survey data).
Comment from nmixter on 15 August 2010 at 23:45
Open up potlatch and compair data to aerial maps to see how it should line up.
Comment from Sanderd17 on 16 August 2010 at 17:47
open up potlatch and compare the roads to the mean of all gps tracks (you can activate all gps-tracks with a little gps button below on the left). If your track is the only one, align it to your track.
Comment from HannesHH on 16 August 2010 at 22:46
From my experience one track is no track. Once you did the same walk several times you will notice how far off GPS can be. The more the merrier, the more the better you can find the golden average.