constraining Error while using lasclip

[Basem Nouh]

Good evening,

i am trying to remove all building from Lidar Data and i have shape files from the City of Bochum (see the photo)

i tried to clip the building but i became always an error.

the code is :
lasclip -cpu64 -lof file_list.17032.txt -merged -poly "H:\Masterarbeit\Masterarbeit\Masterarbeit\HsBo\Geobasis_laz\prozessdatei1_fullarea\clipped_area\2Drop_class\3Unclass\3Unclass\shp\WallSurfaceLod2.shp" -interior -o "merged1.laz"

 

some times i became different constrains number like 2,3,7

i wish any one could give an advice cuz this step is the most important one to get the best DTM

best regards

Basem

[Martin Isenburg]

Hello,

two possibilities:

(1) Likely: The polygons in your SHP file are overlapping or their polygonal lines are crossing. Run some tool that cleans up 2D topologies.

(2) Less likely: After quantizing in a local (!) coordinate system from double to float (as done by lasclip) some line segments become overlapping/crossing. Run some tool that assures the some distances between all polygonal lines.

Regards,

Martin

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[Terje Mathisen]

Martin Isenburg wrote:

Hello,

two possibilities:

(1) Likely: The polygons in your SHP file are overlapping or their polygonal lines are crossing. Run some tool that cleans up 2D topologies.

That seems likely:

After merging several shape files I run the following command to clean up the geometry:

sprintf(q(c:\OSGeo4W64\bin\ogr2ogr "%s" "%s" -dialect sqlite -sql "select st_union(geometry) from '%s'"), $target, $temp_shape, $layer);

Here $temp_layer is the temporary file that results from several update/append operations, $target is the final name, and $layer is the name I've used for the shape file layer.

The key is the sqlite SQL/GIS operation that creates a minimum union of all the source polygons.

Terje

(2) Less likely: After quantizing in a local (!) coordinate system from double to float (as done by lasclip) some line segments become overlapping/crossing. Run some tool that assures the some distances between all polygonal lines.

Regards,

Martin

On Sun, Mar 28, 2021 at 7:26 PM Basem Nouh <basem...@gmail.com> wrote:

Good evening,

i am trying to remove all building from Lidar Data and i have shape files from the City of Bochum (see the photo)

i tried to clip the building but i became always an error.

the code is :
lasclip -cpu64 -lof file_list.17032.txt -merged -poly "H:\Masterarbeit\Masterarbeit\Masterarbeit\HsBo\Geobasis_laz\prozessdatei1_fullarea\clipped_area\2Drop_class\3Unclass\3Unclass\shp\WallSurfaceLod2.shp" -interior -o "merged1.laz"

 

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-- 
- <Terje.M...@tmsw.no>
"almost all programming can be viewed as an exercise in caching"

[Basem Nouh]

Hallo,

which kind of tools should i run to clean up those 2D topologies. is those in Lastools!

or it is better to ask the Office in City of Bochum (Stadtmodelle der stadt Bochum, Amt für Geoinformation) to send me another shape file. Some shape files were not supported according to an error 'unsupported fileshape 31' 

regards,

Basem

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[Knoor, Claudia]

Hello,

 

I suspect that a citygml format (3D buildings) was converted to shape format.

But that doesn't work in your case, because the redundant citygml information was written multiple times in the shape files, so there are many overlays. Furthermore these shapefiles are probably 3D. I guess LAStools software requires 2D-shapes (not sure whether LAStools is able to work with 3D-shapes).

So it will be best to take the „BuildingLoD1Solid-shape“ and convert it to 2D, the other shapefiles are not necessary.

By doing that, clipping should work. But even then there could last some sparse overlays, e.g. in the case of patio roofs.

 

Regards

Claudia

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[Basem Nouh]

Hallo,

i have tried several solution to clean the Shapefile but always i have the same problem 

i tried through Arcgis to repair the Geometry, Multipatch footprint and in Qgis vector clean but Lasclip cannot read the file

which kind of tools i may use !

thanks

Basem

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