OpenStreetMap
So, having signed up three days ago I took special care to note down the names of nearby streets as I passed them. I've corrected over 10 street names in my area, although there were several streets missing from OSM. I'm not sure my cheap GPS is sufficient to map them, as it is only accurate to 0.0001°, and when I tried to measure a short footpath it located one endpoint 14m from the nearest road. Is this GPS simply too inaccurate?
Абмеркаванне
Каментар ад Richard у 9 Сакавік 2009 у 23:40
What model is your GPS? Lots of mappers only use yellow Garmin eTrexes or similar.
Каментар ад davidearl у 10 Сакавік 2009 у 10:23
Welcome Neil,
One degree of latitude is about 111km, so your 0.0001 is about 10m, which is not unusual. No GPS is going to do well in areas of poor signal - if you go down an alleyway with high fences, or an urban canyon, or going through a wood, you'll often lose some or all of the signal. Also it varies according to how many satellites are visible and how low in the sky they are at any one time - you can spend 4 hours mapping and come back to the start point to find it tells you you are 20m away. In the end some interpolation and intelligent interpretation of your tracks is needed to make a good map - you can't follow the trace blindly. It's a good idea in my experience to enter your data as soon as you can so you can remember the area. After a while I find you get a feel for the 'birds-eye view', that some streets are laid out parallel to each other or there is some systematic model behind the layout which can guide you, even in apparently haphazard surroundings. Often culs-de-sac require you to retrace your steps, but this isn't necessarily a bad thing as you get two traces and can often see where there was a bad one. Bear in mind most suburban roads are 8-10m wide, plus say 3m for a verge or footway, so the trace along one side of a road could well be 10m from the end of an alleyway emerging onto the road. Also, if you're co-ordinating with someone else's traces, they could be 10m out as well, so 20m between you. Or they could just have had an off day and simply got it wrong.
Making corrections to names is really helpful. If you're finding quite a few streets missing, you probably want to do a systematic survey of the area as the person who did them clearly hasn't been very helpful in doing some streets and not others. Randomly adding streets isn't all that helpful as it gives a misleading impression of completeness and discourages proper surveys of an area. Obviously a skeleton of main roads is useful, but to randomly put some side streets in an area in and not others just means someone else has to do it all again later because you don't know what streets off the ones that have been marked are missing.
Каментар ад Biogenesis_ у 13 Сакавік 2009 у 08:09
Or you can use the Maplint layer to see which streets don't have names yet, that makes it much easier to plan mapping trips :).
Каментар ад ArtyCarty479831 у 13 Сакавік 2009 у 15:58
My first GPS unit wasn't very accurate, but I found that if I visited somewhere several times, the averages came out pretty good.