[gdal-dev] Improve clipping of shapefiles

[Jan Heckman]

Can't really help you with the OGR part, however, I wrote utilities do
solve this (really) fast for calculating grids based on this type of
intersection.
Speed is often a matter of using specific tools utilizing the
characteristics of the problem, i.c. the fishnet regularities.
Can you share the shapesfiles so I can try?
Regards,
Jan

On Mon, Sep 11, 2017 at 11:09 AM, Paul Meems <bontepaarden at gmail.com> wrote:

> I have a large shapefile with over 2.8 million shapes (fishnet) and I have
> a border file with only 1 multipolygon.
>
> I'm trying to clip the fishnet with the border.
> Using code is takes about 5 min. using command line it takes even longer.
>
> This is my command:
> ogr2ogr fishnetClipped.shp fishnet.shp -clipsrc border.shp
>
> And this is my C# code:
> using (var dsFishnet = Ogr.Open(fishnetFilename, 0))
> {
>     // Select first layer:
>     using (var layerFishnet = dsFishnet.GetLayerByIndex(0))
>     {
>         // Open border:
>         using (var dsBorder = Ogr.Open(borderFilename, 0))
>         {
>             // Select first layer:
>             using (var layerBorder = dsBorder.GetLayerByIndex(0))
>             {
>                 // Get ESRI driver:
>                 using (var driver = Ogr.GetDriverByName("ESRI Shapefile"))
>                 {
>                     // Create new shapefile:
>                     using (var dsClipped = driver.CreateDataSource(outputFilename,
> new string[] { }))
>                     {
>                         // Create new layer:
>                         var layerName = Path.GetFileNameWithoutExtension(
> outputFilename);
>                         using (var layerClipped = dsClipped.CreateLayer(layerName,
> layerFishnet.GetSpatialRef(), layerFishnet.GetGeomType(), new string[] { }))
>                         {
>                             if (layerClipped == null)
>                             {
>                                 throw new Exception("Layer creation
> failed.");
>                             }
>
>                             // Clip the layer:
>                             layerFishnet.Clip(layerBorder, layerClipped,
> null, null, null);
>                         }
>                     }
>                 }
>             }
>         }
>     }
> }
>
> I'm using GDAL 2.1.3
>
> Can I somehow improve the speed?
> I read something about putting one of the layers in memory or using a
> spatial filter.
> But I can't find an example of how to do this.
>
> Please advise.
>
> Thanks,
> Paul
>
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>
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