On 01/01/2010 14:14, Steve Bennett wrote: > On Sat, Jan 2, 2010 at 12:54 AM, Shaun McDonald > <sh...@shaunmcdonald.me.uk <mailto:sh...@shaunmcdonald.me.uk>> wrote: > > It is very common for GPSs to give errors for whatever reason. > Interference is very common from things like buildings. Newer units > are less likely to have an issue. You simply need to go along that > track again a few times to get an averaged out reading. > > > Well...ok. But in this case I have the aerial photography, so I can just > trace it, once I know more or less where the path goes. I was just > curious if there was a way to detect errors at the time - repeating > every trace several times "just in case" would be pretty inefficient.
You can check the satellite screen on the Garmin. It should show an estimated position accuracy. Also, you can look at which satellites its receiving. If its locked on to a reasonable number of satellites in a decent spread across the sky, you can be fairly confident in its accuracy. You don't have any sort of WAAS like system in you part of the world do you? That would help a bit. But I'd still agree with Shaun - a single GPS trace is not really accurate enough for adding ways to OSM IMO. I'd say get at least 2, preferably 1 in each direction. If they are close to each other you can be confident its probably accurate. If they are much different, its worth getting a few more traces and taking an average. Though yes, this is not really necessary if you have accurate aerial photography that you can trace from. Craig _______________________________________________ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
