[talk-au] GPS accuracy

[Abhi Beckert]

On the topic of accuracy, some GPS's also have gyroscopes and accelerometers and compasses to error correct the GPS data. They're getting complicated enough now I don't like to comment on when/where they work well. There's just too many variables the algorithms are tweaked constantly by software updates.

On 21/09/2012, at 9:38, Brett Russell <brussell237 at live.com.au> wrote:

> My goal is pratical accuracy.  By that, avoiding my GPS complaining with OSM that I am heading into oncomming traffic.  The issue with that was the particular road was aligned to native Bing so was say five to ten metres out.  If I can establish the correct alignment of Bing for the area then I can have the road in the correct place.  Now of course if my GPS can not resolve to the necessary accuracy then I still will have the issue but that is between my GPS and OSM rather than OSM and the real position.

I find the only way to get an accurate road position, especially corners/intersections or in poor signal areas, is to make several traces.

But honestly I don't worry about it too much. A road that is 10 or even 50 meters off is better than no road at all on the map (especially in remote areas where most of the missing roads are). If I've only got a single poor quality trace I'll still put it in. Somebody else (or maybe me) will notice eventually and take the time to replace it with more accurate data.

When reading the map, a GPS needs to allow for inaccuracies in it's own signal anyway, so in practice they handle it well.

Of course, make it as good as you can, and fix other people's inaccurate data when you notice it, but I'm just saying if you have a bad trace and don't plan to drive down the road again 5 more times, by all means put what you've got on the map.

When I know my trace is bad, I like to enter it with big gaps between each point, so you see straight lines and hard corners instead of a nicely flowing road on the map.

>  Gradually working my way around Tassie by lake tracing and that is where I am understanding the challenges Bing gives you.  Its image quality ranges from top class to murky but still great to have it as the alternative would be walking around every lake, tarn and pool.

Sometimes I load my traces into google earth, since that has much higher quality satellite photos, to get an idea how far off my trace is.

- Abhi

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