[OSM-dev] curves

[Artem Pavlenko]

On 3 Jan 2008, at 18:19, Martijn van Oosterhout wrote:

> On Jan 3, 2008 6:29 PM, Artem Pavlenko  
> <artem.mapnik at googlemail.com> wrote:
>> 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).
>
> I think if you defined a POLYLINE in such a way that every second
> point is a control point then I think that would be efficient to store
> and draw and all the existing infrastructure will probably just work
> fine... IIRC the curve is then bounden by lines joining the base
> points and the control points.

The above might well work but wouldn't cover situations (most of the  
time) when we need combination
of straight segments and curves.

Postgresql can be easily extended to support custom data types and  
use spatial indexing (GIST implemented in Postgresql not in PostGIS).
In fact the only spatial operator we use is '&&' . What would be  
really cool is to have multi-resolution blob, with ability to extract  
geometry for each defined zoom level (scale).

Artem

>
> Note: the patent posted talks about storing *altitude* data or roads
> this way and thus doesn't apply in this situation.
>
> Have a nice day,
> -- 
> Martijn van Oosterhout <kleptog at gmail.com> http://svana.org/kleptog/