[postgis-users] Postgis and Dynamic Segmentation

[Christoph Spoerri]

I implemented some basic dyn. segmentation functions (aka linear referencing) 
on top of the existing geometries (3D lines) and use the Z value as the M (- 
measure) value. I'm planning to migrate the function to the new LWGEOM over 
the next few weeks. 

The functions are written in C and include functions for:
- creating measures on geometries
- returning a new shape based on from/to arguments (or only from in case of 
points)
- return the 'measure' for a given location along the point

If somebody is interested in the code, let me know and I can send it along.

cheers,
Christoph

BTW. when will the new LWGEOM format be released? Will it work transparently 
with the exiting geometry format? It would be good to know, so that any 
development efforts can be put into the 'correct' format.

On Thursday 06 May 2004 12:20, David Blasby wrote:
> Düster Horst wrote:
> > I developed a first draft plpgsql function to create dynamic segmentated
> > linestrings (see attachment). The function works with a little numer of
> > linestrings. With larger datasets it works to slow.
> >
> > I send the function code to the list to hope for an idea to accelerate
> > this function. Perhaps it is possible to create and integrate a C based
> > function dynseg like line_interpolate_point to postgis.
>
> This looks interesting.
>
> You didnt put "line_interpolate_point()" in the .sql file.
>
> A function like this would be reasonably easy to do in C.  You might
> want to look at the LWGEOM stuff (see the postgis developers mailing
> list) since its easier to write C function because of the API.
>
> There's lots and lots of example functions in PostGIS if you wanted to
> know how to add it.
>
> dave
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