[Talk-us] Over-digitized imports?

Zeke Farwell ezekielf at gmail.com
Tue Aug 24 16:51:21 BST 2010


In looking at some of those ways I'd say your simplification is completely
warranted.  The curves still look very smooth after you've removed 73% of
the nodes.

I agree with others that storage is cheap and saving space in the DB may not
be that important.  More nodes make for smoother, more detailed ways but
after a certain density is reached more nodes offer diminishing
returns.  Also when nodes are very dense on a way it becomes hard to select
said way with out zooming very far in.    Clearly there's no need to
systematically remove excess nodes on already imported data, but if
simplifying a way makes your editing easier and doesn't reduce the
detail/smoothness (clearly this is a judgement call) I say go for it.

Zeke


On Tue, Aug 24, 2010 at 4:14 AM, Alan Mintz
<Alan_Mintz+OSM at earthlink.net<Alan_Mintz%2BOSM at earthlink.net>
> wrote:

> At 2010-08-19 20:24, Alan Mintz wrote:
>
>> I'm mapping in this area:
>> http://www.openstreetmap.org/?lat=34.08242&lon=-118.639&zoom=17
>>
>> Along the north side of the tertiary road (whose name is not rendered, but
>> is Saddle Peak Road) is a state park polygon (Topanga State Park) imported
>> from CASIL. In this small segment, the road is approximated with less than
>> 70 nodes, while the park polygon segment alongside uses over 1200. I've
>> noticed similar "beauty" in other data from this source and others (like the
>> Bakersfield data mentioned recently on the list).
>>
>> Should imports make an effort to "un-smooth" such data to some extent, for
>> the benefit of editing and rendering performance, storage, etc?
>>
>
> As a test case, I used JOSM's "Simplify Way" on the ways that make up
> Topanga State Park. After playing around a bit, in advanced preferences, I
> set simplify-way.max-error to 0.2, which still modeled curves to maybe
> single-digit meter errors, yet removed 73% of the nodes (from 9103 to 2466).
>
> The ways are:
> 38458997
> 38459009
> 38459010
> 38459013
> 45753168
> 45753173
> 45753175
>
> I'm not embarking on a mission to simplify all ways - just taking the
> (short time) to do this when I'm mapping an area anyway and see it could be
> of benefit.
>
> --
> Alan Mintz <Alan_Mintz+OSM at Earthlink.net>
>
>
>
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