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Author Topic: Parameters for the classification of points within the dense cloud  (Read 169 times)

ajpancha

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Greetings, please could you help me with some tips for the classification of points within the cloud of dense points, especially to separate points of land, vegetation and building ...

Within PHOTOSCAN, TOOLS menu, there is an option to classify points, but it asks me to enter certain parameters for the automatic classification, these parameters are not clear on how to assign them, they could indicate what values could be placed in each one, it is based on terrain and how could these parameters vary for flat, semi-mountainous, totally mountainous terrain ...

I appreciate your comments ...

Atte.

stihl

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Re: Parameters for the classification of points within the dense cloud
« Reply #1 on: July 16, 2018, 11:17:05 AM »
From the manual:

Max angle (deg)
Determines one of the conditions to be checked while testing a point as a ground one, i.e. sets limitation
for an angle between terrain model and the line to connect the point in question with a point from a
ground class. For nearly flat terrain it is recommended to use default value of 15 deg for the parameter.
It is reasonable to set a higher value, if the terrain contains steep slopes.
Max distance (m)
Determines one of the conditions to be checked while testing a point as a ground one, i.e. sets limitation
for a distance between the point in question and terrain model. In fact, this parameter determines the
assumption for the maximum variation of the ground elevation at a time.
Cell size (m)
Determines  the  size  of  the  cells  for  point  cloud  to  be  divided  into  as  a  preparatory  step  in  ground
points classification procedure. Cell size should be indicated with respect to the size of the largest
area within the scene that does not contain any ground points, e. g. building or close forest.


Is this clear to you?

ajpancha

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Re: Parameters for the classification of points within the dense cloud
« Reply #2 on: July 19, 2018, 04:48:10 PM »
...
Greetings from a distance Stihl, thank you very much for the comment, gave me the idea to be able to make the classification of the points ...

I had to play with the parameters, see the difference and the different results I got with each parameter, my terrain is not so wavy, and the parameters I chose were: maximum angle 15 °, maximum distance 0.05 and cell size 10, between all the parameters, the indicated one gave me a better result classifying almost all the points of terrain, I hope to have implemented well my criteria for that selection ...

In any case, I would appreciate very much that based on your experience you can indicate any observations or recommendations to be taken into account in this procedure in the future ...

Again, thank you very much for the response, have a nice day ..

Atte.