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

Markus Neteler neteler at itc.it
Mon Jun 26 03:11:35 EDT 2006


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).

thanks for a hint

 Markus



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