OpenStreetMap
I'm really getting into the swing of this. I have been walking the streets of my local area and getting lots of gps tracks.
I've started to notice that several roads don't match my tracks. I've driven and walked these roads and sometimes the road is about 20m off the track.
Is there anything I should do before making to many changes ot other people's work. To avoid stepping on people's toes or making my own mistakes.....
Parola
Comentario de Guillaume Audirac no 11 de Xuño de 2009 ás 03:13
Hi,
I noticed sometimes the same. It can take some time before the GPS gives accurate data (and 20m is not so far from the GPS limit). It depends on its sensitivity, the weather, etc... From my experience, I don't change the other tracks if my GPS was not switched on since 1/2 hour. After collecting the some roads again and again, I don't bother too much on accuracy, if my data fits properly with the surrounding (points of interests, buildings, crossing roads...).
Comentario de c2r no 11 de Xuño de 2009 ás 06:13
Take a look here, and press G:
osm.org/edit?lat=51.82092&lon=-0.01608&zoom=17
You can see the map overlay, with the blue GPS trail beneath it.
The footpath in red runs in a straight line, but notice how the GPS is zig-zagging at either side into the field... I was walking fairly straight, so the zig-zagging must be an inaccuracy in the GPS. Weather was awful when I was walking.
Regards
Chris
Comentario de DCWells no 11 de Xuño de 2009 ás 07:58
Are you sure you hadn't been drinking Chris ;-)
Thanks for the hints. I've been keeping an eye on the GPS sat fix and it generally has 7 or 8 sats and reports an accuracy of 5m which I'm pretty pleased with. I guess I basically need to collect repetitive data and make sure it fits in with other land marks. It seams to be mainly the smaller residential roads which are out. The main roads are accurate to my track logs so I wonder if the residential roads might have been done from knowing the area rather than GPS surveying.....
Comentario de chillly no 11 de Xuño de 2009 ás 12:13
If you think you can improve the accuracy of a road then just do it. It is a wiki, so your improvements can always be improved again. Using multiple GPS tracks, taken on different days, to estimate the best place for a road helps, but if you know you have an good accuracy then use it. It is best to move an existing road rather than to delete it and add a new one.
Comentario de HannesHH no 12 de Xuño de 2009 ás 07:14
It really helps to let the GPS "find itself" by letting it rest in a stationary place. Getting the position and good satellite reception is much faster than when in motion.