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Question

Breaklines and Isohypse generation


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Hello,

 

 

I am dealing with large LAS file that is output of AgiSoft Photoscan. I need to generate break lines and isohypses.

 

In this question I have seen the potential solution but I think this can't solve both of my needs. I hope I can get some hint.

 

 

Thank you all in advance,

With respect,

 

Dejan

5 replies

stalknecht
Contributor
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  • Contributor
  • July 22, 2018

 

What do you mean by break lines?

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stalknecht wrote:

 

What do you mean by break lines?
A break-line is extracted as a characteristic part such as an edge of stack or a corner of building by a laser scanner measurement result (Point Cloud Data). A breakline is a vector-based feature (polyline, polygon) added to a 3D model.

 

There are many software that do that but I am trying to do it with FME. I have done the part of isohypses but I don't know how to generate break lines.

 

Any hint would be useful.

 

Thank You in advance!

 

 


redgeographics
Celebrity
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Wild idea: generate a tin and look for triangles that are very steep, then dissolve them and generate centerlines.

In theory it should work as long as your LAS is detailed enough. But... that'll increase processing time.


daveatsafe
Safer
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  • Safer
  • July 25, 2018

Another suggestion for extracting the breaklines:

- Use the TinGenerator to generate triangles and TINedges

- Send the triangles to a PlanarityFilter with expose surface normal set to yes

- Send the edges to a CoordinateExtractor to store the 3D coordinates

- Send both streams to a TopologyBuilder, with propagate All Attributes set to yes. This will produce edges that have the surface normal for each adjoining triangle.

The TopologyBuilder will force the edges to 2D, but you can use the stored coordinates to restore the original geometry. By comparing the normals of the adjoining triangles, you can determine if the edge should be a break line or not.


Forum|alt.badge.img
  • April 12, 2019

Were you able to find a solution to this? I found this question looking for answers to the same problem. I'm just starting and am trying the suggestions offered in the replies.

Thanks,

Justin


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