[OSM-dev] curves

[Artem Pavlenko]

On 3 Jan 2008, at 16:53, Frederik Ramm wrote:

> Hi,
>
>>> 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).

>
> Bye
> Frederik

Cheers
Artem