[Java-collab] Introduction

[Jody Garnett]

Very Fun Markus:

The approach to curves matches what I had in mind; I was going to do  
it as an extension to JTS Geometry but that is more of interest if we  
wanted to keep working with JTS Geometry API.

In anycase this sounds like a great area for collaboration; the  
iso19107 geometry api is not intergrated into geotools at the moment  
so both ways forward represent similar amounts of work. We actually  
have a team looking at doing this work over the next two years (so it  
would be good to sort out a way forward).

As for PostGIS; if you can store your origional curve in the new  
extensions to WKB can you just drop your linearized representation (ie  
there is no point in storing it...).

Jody

On 30/06/2009, at 1:02 AM, Markus Schneider wrote:

> As Andrea already knows, we're trying to keep the implementation  
> effort as low as possible. Therefore, our approach is
> not extending JTS, but using wrappers around JTS geometries, that  
> can cope with simple and complex geometries:
>
> - In case of a simple geometry (Point, LineString, Polygon), the  
> wrapper is totally straightforward, e.g. calls to
> #intersects() are just passed to JTS.
> - For complex ones (e.g. curves with non-linear segments), the curve  
> parameters are stored in the wrapper and
> additionally, a linearized version is generated (represented using  
> JTS) that is used to evaluate spatial predicates.
>
> A major benefit of this approach is that it is also applicable to  
> backends (e.g. PostGIS). We would store a linearized
> version as a native PostGIS geometry (used for the topological  
> predicates), and store a BLOB beside it that stores the
> original curve segments and their parameters (only necessary when  
> curve is not a linestring).
>
> Obviously, this approach is restriced to operations on the footprint  
> when dealing with 3D-geometries. But this is still
> better than nothing :-) Getting a 3D-BBox-operator working should be  
> manageble, though.
>
> Best regards,
> Markus
>
> Andrea Aime wrote:
>> Jody Garnett ha scritto:
>>> Note I am serious about the Curve thing...
>>> - It is strategic work - supporting the WKB format
>>> - PostGIS / GEOS is starting moving on it
>>> - JTS won't touch it so it is up to us :-D
>>>
>>> Mark Leslie and myself had some blog posts on it a couple months  
>>> back;
>>> another idea in search of time/funds/hapless volunteer :-D
>>>
>>> It also makes sense to walk before we can run; Curve is a smaller
>>> problem then Geometry and is not one currently addressed?
>>
>> Jody, DeeGree has this nice geometry library and they are interested
>> is sharing the load on it as a whole. I believe it's well worth  
>> looking
>> into.
>>
>> Cheers
>> Andrea
>>
>
>
> -- 
> Markus Schneider
>
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