lasheight

[Karin...@ldbv.bayern.de]

Hello Martin,

 

with lasheight there is the option to save the height above ground as extra bytes (-store_as_extra_bytes)

Is there a way to access the computed heights?

 

I want to use this for the detection of power lines and power poles.

 

Thanks

 

Karin

 

 

 

[Martin Isenburg]

Hello Karin,

There are a number of ways to use additional per-point attributes that are stored as "extra bytes" and documented with a VLR with the user ID "LASF_Spec" and record ID "4" as described in the LAS 1.4 specification document. You can, for example, on-the-fly copy this attribute into the z coordinate of each LAS point using the LAStransform '-copy_attribute_into_z 0' with 0 being the index of the attribute. You can also filter points based on their attribute values using the corresponding on-the-fly filter command line switches. Run 'las2las -h' for an up-to-date list.

You can also use the height above ground for classifications in lasclassify and for metric generation in lascanopy (just see the respective README files for details).

With lasgrid and las2dem you can also grid or interpolate any of the additional attribute stored per-point using the appropriate switch such as '-attribute 0' and so on.

Let me know what other uses for the additional per-point attributes stored in the extra bytes of each point you are in need of.

Regards,

Martin

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[Martin Isenburg]

Hello Karin,

There are a number of ways to use additional per-point attributes that are stored as "extra bytes" and documented with a VLR with the user ID "LASF_Spec" and record ID "4" as described in the LAS 1.4 specification document. You can, for example, on-the-fly copy this attribute into the z coordinate of each LAS point using the LAStransform '-copy_attribute_into_z 0' with 0 being the index of the attribute. You can also filter points based on their attribute values using the corresponding on-the-fly filter command line switches. Run 'las2las -h' for an up-to-date list.

You can also use the height above ground for classifications in lasclassify and for metric generation in lascanopy (just see the respective README files for details).

With lasgrid and las2dem you can also grid or interpolate any of the additional attribute stored per-point using the appropriate switch such as '-attribute 0' and so on.

Let me know what other uses for the additional per-point attributes stored in the extra bytes of each point you are in need of.

Regards,

Martin

On Dec 13, 2017 09:51, <Karin...@ldbv.bayern.de> wrote:

--

[Karin...@ldbv.bayern.de]

Hello Martin,

 

thank you for  the detailed information.

Gridding the points with the height above ground visualizes the power lines and the power poles nicely if the point density is high enough. We then digitize the exact position of the poles.

The result is a point shape.

Now I am interested in the height of the pole. Up to now I clip all the positions (point shape with a buffer of 3m),

subsequently do a thinning with a grid spacing of 15m ( keeping only the highest or alternatively the lowest point in the cell).

This gives reasonable results but I would prefer to directly use the (buffered) point position to get more reliable heights.

 

Is there any workflow to achieve this with LAStools?

 

Regards,

Karin