[Openstreetmap-dev] curves

Andy Robinson Andy_J_Robinson at blueyonder.co.uk
Wed Jan 18 09:41:04 GMT 2006


Overall I agree with Tom here. However if a curve implementation within the
database has a benefit over the sheer number of nodes and segments required
to make up curves using multiple segments then its obviously worth
considering. 

Of course the ultimate direction would be to make the features as accurate
(in terms of shape) as they are on the ground. Nowadays, in the UK at least,
all roads are made up from the occasional straight section, transition
curves (splines) and constant radius curves. Changing from one shape to
another is always made with a spline. In reality that's what existing roads
are because over time, older roads have been upgraded and the above is
effectively what occurs even if you can't actually discern in.

Cheers,
Andy

Andy Robinson
Andy_J_Robinson at blueyonder.co.uk 

>-----Original Message-----
>From: openstreetmap-dev-bounces at vr.ucl.ac.uk [mailto:openstreetmap-dev-
>bounces at vr.ucl.ac.uk] On Behalf Of Tom Carden
>Sent: 18 January 2006 09:30
>To: openstreetmap-dev at vr.ucl.ac.uk
>Subject: Re: [Openstreetmap-dev] curves
>
>> My experience of street network data in GIS is that it doesn't usually
>use
>> curves at all. Everything is points and straight lines, or polylines, and
>> although it looks crude at very close zooms the data is always good
>> enough.
>>
>
>Interesting.  We can do better than that then :)
>
>> I wonder if curves are going to add to the complexity of the applet and
>> also data export, without really giving a lot of benefit in terms of
>> additional data. Wouldn't point and line data be more portable into other
>> formats in the future? Just a thought.
>>
>
>Right now, I agree.
>
>I don't think it's worth putting much effort into writing curve software
>right now. As you can see from the wiki page, it's going to be hard to
>settle on the ideal curve type - what's important for the editor (speed,
>ease of use) isn't important for print maps (quality, clarity) for
>example.  Also, editing curves is a bit of an art form, and adding it into
>the OSM editors might needlessly raise the bar for editing.
>
>Not to mention that other things are more pressing (selecting multiple
>segments for naming, and tagging streets as motorway/footpath/rail in the
>applet, to name my favourite two).  Adding curves would also needlessly
>raise the bar for writing clients.
>
>I wouldn't sweat it over curves when refactoring the database - if
>necessary, the modifications can be made at a later date.
>
>Tom.
>
>
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