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#1 2011-12-16 09:51:58

Russ McD
Member
From: Hereford & Chiang Mai.
Registered: 2011-04-17
Posts: 289

Simplify Accuracy Slider

Can anyone explain the function of the "Simplify Accuracy" Slider that is now found under the Options button in Potlatch 2 ?
Rgds,

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#2 2012-01-29 23:13:57

stephankn
Moderator
Registered: 2010-05-04
Posts: 606

Re: Simplify Accuracy Slider

That function removes points from a line Potlach thinks are useless.
You should never use this functionality on ways you did not create by yourself. People might have put a node in the middle of a straight way to indicate something, maybe a hint for them to continue mapping. Potlach would remove that point.
Automatically removing accuracy from ways other mappers had invested a lot of time could be considered vandalism.

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#3 2012-03-30 19:18:19

Russ McD
Member
From: Hereford & Chiang Mai.
Registered: 2011-04-17
Posts: 289

Re: Simplify Accuracy Slider

Stephan
Thanks for that, and I have noted what you say about using on other users ways.
Could you briefly explain how the function works ..... do you highlight the way, and then adjust the slider ?
I guess its useful for GPS traces, but maybe not for armchair mappers, where the insertion of nodes is regulated by common sense, and by definition, then doesn't need reducing.
Rgds, Russ.

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#4 2012-03-31 04:08:57

stephankn
Moderator
Registered: 2010-05-04
Posts: 606

Re: Simplify Accuracy Slider

Yes, it is intended for ways that are automatically created out of GPS points.

doing so is also discouraged.

The algorithm might be a Douglas Peucker implementation, or very similar.
http://en.wikipedia.org/wiki/Ramer%E2%8 … _algorithm

Best is to upload the GPS tracks to openstreetmap (probably remove places where you forgot to turn off GPS like restaurants or convenience stores). Then display these points on top of aerial imagery helping to align it.
Then get the geometry from there and add your tagging.

Stephan

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#5 2012-04-04 07:30:20

Russ McD
Member
From: Hereford & Chiang Mai.
Registered: 2011-04-17
Posts: 289

Re: Simplify Accuracy Slider

Thanks Stephan,
As I tend to use Potlatch 2, there doesn't seem to be a function to automatically put nodes on a GPS track, so I end up tracing the tracks manually.
And I think, in fairness, although more time consuming, it gives a far more "useful" trace... as u say, it gives u a chance to manually ignore the spikes, & restaurant stops, etc. and also, it enhances the precision of places like hairpin bends, where the GPS track often squares them off, or cuts them short.
Rgds, Russ.

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