[Gdal-dev] Breaking long lines/boundaries with OGR function?

[Markus Neteler]

On Mon, Jun 26, 2006 at 11:15:06AM -0400, Frank Warmerdam wrote:
> Markus Neteler wrote:
> >Hi,
> >
> >the following issue came up in GRASS:
> >v.in.ogr, the OGR based import tool, may take a long time if
> >the data contains long complicated polylines.
> >
> >>From TODO
> >http://freegis.org/cgi-bin/viewcvs.cgi/grass6/doc/vector/TODO
> >>============================
> >>v.in.ogr
> >>--------
> >>It would be useful to split long boundaries to smaller
> >>pieces. Otherwise cleaning process can become very slow because
> >>bounding box of long boundaries can overlap large part of the map (for
> >>example outline around all areas) and cleaning process is checking
> >>intersection with all boundaries falling in the bounding box.
> >>============================
> >
> >Since I don't know OGR well enough, is there any function 
> >we could make use of to achieve splitting of long lines before
> >handing data over to (topological) GRASS?
> >
> >I found 
> >http://ogr.maptools.org/drv_dgn.html
> >"Polygons and line strings with too many vertices will be split into
> > a group of elmements prefixed with a Complex Shape Header or Complex
> > Chain Header element as appropriate."
> >
> >Something seems to be there (or nearby).
> 
> Markus,
> 
> It would not be particularly hard to have v.in.ogr break linestrings with
> a lot of vertices into distinct geometries though it isn't clear to me
> that this would really accelerate topology building.  There is no "canned"
> method in OGR for splitting features though.

Frank,

the relevant geometric portion was written by Radim who currently changes
the job. I am not familiar with internal details - just hoped to find
an OGR shortcut to accelerate the thing according to Radim's hints
on v.in.ogr.

thanks

 Markus