manage holes with lasboundary

[Giuseppe Gentili]

Hello,

I've applied the -holes parameter to get the 'exact' boundary polygon for points of laz file (see the laz.jpg attached file)

The interior polygon of the hole was generated as well as the exterior polygon as  shown in the bnd.jpg attached file: I got two diferent polygons

The expected result was to have the exterior polygon really holed in order to represent actually the content of the laz file.

Any suggestion how to get the expected result ?

Many thanks in advance for your reply.
Giuseppe

P.S. I have attached  the attached laz file too

[Paul Manley]

Adding a comment to see any answers. Having the same issue with buildings.

[Martin Isenburg]

Hello,

sorry. This has not been implemented yet. It's on the TO DO list.

Regards,

Martin

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[Auksinis Arbūzas]

Is there another solution for getting a boundary polygon with holes extracted, perhaps with an additional process with a different software? I cannot find a way to check whether the polygon in the file is a hole or not, so can't figure out how to remove the holes from the main polygon. If -labels is used, all features are populated by the same data of the entire LAS file.

[Jorge Delgado García]

I think there is a problem of interpretation of the command, when it is said that lasboundary detects -holes is that it detects polygons in which no data has been captured (for example, because of some problem in the capture). I get the impression that it is meant to detect points with abnormally low dimensions, which should be done with lasnoise (for example). A very interesting utility of this application of lasboundary is to be able to determine in a previous quality control, what is the real coverage of the captured data and the occurrences produced, it can be completed with lasgrid to obtain a representation of the density of points according to a mesh (-point_density option).
It is evident, that in this case, the polygons only cover areas that are not covered, the information refers to the source file, and logically no reference appears to the number of points included because as I said there are none. If desired as these polygons are stored in SHP format, for example, it is possible to perform any type of calculation of area, perimeter, shape, with a GIS.
I hope I have clarified the matter a little, to illustrate it a little more a couple of figures from a real example in Spain.

Jorge Delgado

University of Jaén

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[Ringle, Bill]

If you export them as a GIS file, you could test how many points are within each polygon via a spatial join.

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Subject: Re: [LAStools] Re: manage holes with lasboundary

 

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[Auksinis Arbūzas]

Could you please clarify? How can spatial join be used for testing which polygons are actually holes?

---------- Forwarded message ---------
From: biringle <Unknown>
Date: Friday, January 27, 2023 at 12:44:06 AM UTC+2
Subject: Re: [LAStools] Re: manage holes with lasboundary
To: last...@googlegroups.com <Unknown>

If you export them as a GIS file, you could test how many points are within each polygon via a spatial join.

[Ringle, Bill]

I am thinking of the ArcGIS tool here. You would import your polygons as one layer, your lidar points as another (check help on LASD files if you don't know how to do this). Then use the option on the polygon layer by right clicking on it, selecting join, then spatial join. Make your lidar point the join layer. The output of this will be a copy of your polygon file, but with an added field "COUNTS", which will contain the number of lidar points falling within the polygon. You can then select on that field as needed.

You might also calculate the area of each polygon and then the density of points within each one. This might be a better metric, as a 1 ha polygon with one or two points is essentially empty.

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Sent: Friday, January 27, 2023 9:13 AM

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