artem.mapnik at googlemail.com
Thu Jan 3 17:29:22 GMT 2008
On 3 Jan 2008, at 16:53, Frederik Ramm wrote:
>>> What people think about explicitly supporting curves as a part
>>> of geometry model? This way we can model the world better.
>> When I suggested this before, someone said it was patented,
>> possibly by
>> either NavTeq or TeleAtlas,
> Navteq seem to have a patent on using Bezier curves for road
> network representation or something. It was on the lists here.
It must be more then just representation of road network. There are
so much prior art - CAD and even some 70s GIS could do bezier curves.
> I also find the idea very tempting, however one has to bear in mind
> that some things could then become very difficult. For example,
> computing the combined length of all motorways is trivial today,
> and will probably require specialist tools if we go Bezier.
> Equally, finding intersections and the like (think Validator
> plugin) - probably a computational nightmare if Beziers are involved.
Yes, true. One way to deal with beziers is to convert them to
polylines (easy) when computing intersection , length etc.
> Will the built-in PostGIS stuff ("give me everything that
> intersects with this rectangle") work out-of-the box with Beziers?
No. PostGIS doesn't support beziers. But spatial queries like
'intersect', 'within' are usually implemented as two step process:
1. check if geometry bbox intersects query bbox
2. refine query based on results from (1).
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