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Author Topic: classify ground poins  (Read 9329 times)

frank.stremke

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classify ground poins
« on: October 22, 2013, 03:48:28 PM »
hi
just came along this nice new feature and a test with default setings gave impresive results however i would be thankfull for some more insight into the actual setings and what they do.
the helpfile does not help since it seems to be from the old version.
best regards
frank

Alexey Pasumansky

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Re: classify ground poins
« Reply #1 on: October 22, 2013, 03:50:29 PM »
Hello Frank,

Here's the brief description already posted in "1.0.0 pre-release" topic:

Quote
Automatic dense point cloud classification finds points from the two classes: Ground and Low Points (that are under the estimated ground level). Manual classification allows to assign classes to the selected points.
It's recommended to use default values in Classify Ground Points dialog, but they can be slightly varied depending on the project.

Generally the method is the following: at first in every cell the lowest point is selected (Cell Size should be adjusted so that there are guarantied ground points in each cell). Then these points for each cell are triangulated in grid that should not be laying above the ground. Then new points are added to this grid - each of the points being added should match the following criteria:
the distance between the point and the "ground surface" should not be bigger than Max.Distance parameter; the angles between the "ground" and the vectors connecting the point and vertices of the corresponding cells are not greater then Max.Angle parameter.

Later in the Build Mesh dialog you can choose classes that should be used for mesh generation.
Best regards,
Alexey Pasumansky,
Agisoft LLC

frank.stremke

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Re: classify ground poins
« Reply #2 on: October 22, 2013, 03:59:09 PM »
thanks that will do for now is it also posible to remove vegetation with this tool as from my understanding it should be by some trail and error :-D
thanks
frank

RodneyPilbrow

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Re: classify ground poins
« Reply #3 on: January 01, 2014, 06:57:27 AM »
Alexey, can you clarify whether the max distance parameter is a height above the initial grid which is formed from the low points in each cell?

Alexey Pasumansky

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Re: classify ground poins
« Reply #4 on: January 01, 2014, 12:04:50 PM »
Hello Rodney,

Max distance parameter value is used on every iteration of classification procedure. So it is used for comparison with the current grid and not with the initial one.
Best regards,
Alexey Pasumansky,
Agisoft LLC

Alexey Pasumansky

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Re: classify ground poins
« Reply #5 on: January 16, 2014, 05:59:32 PM »
Tutorial regarding dense cloud classification instruments is available in Tutorial section:


http://www.agisoft.ru/tutorials/photoscan/08/
Best regards,
Alexey Pasumansky,
Agisoft LLC