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

[Ari Jolma]

Markus,

I'm not sure why the import should be effected by the spatial extents etc. In my
code I "import" data from OGR each time I render it and there's no big overhead
because of that. The code is also extremely simple. What would you consider
"complicated"? I've for example looked at ghssh coastline data and they render
reasonably fast.

Of course I don't know much about the way GRASS stored vector data or about the
import tool :-)

Ari

On Mon, 26 Jun 2006 09:11:35 +0200 Markus Neteler <neteler at itc.it> 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).
> 
> thanks for a hint
> 
>  Markus
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-- 
Prof. Ari Jolma
Kartografia ja Geoinformatiikka / Cartography and Geoinformatics
Teknillinen Korkeakoulu / Helsinki University of Technology
POBox 1200, 02015 TKK, Finland
Email: ari.jolma at tkk.fi URL: http://www.tkk.fi/~jolma