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

[Frank Warmerdam]

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.

Best regards,
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