Is there any documentation...

Added by Allen Duncan over 5 years ago


Is there any documentation to assist with the newly added SEGMA plugin?


Replies (2)

RE: Is there any documentation... - Added by Piboule Alexandre over 5 years ago


A tutorial is planned, but I can’t give you a specific date.

In the meantime, here is the sequence of steps to use in the case of a point cloud with Z = height:

1) Load the point cloud
2) Create the DSM: Rasters / Images, Digital Elevation Models, Create DSM (Zmax). Check the scene, choose resolution.
3) Apply a pit filling step: here you have two choices:
  • Rasters / Images, Digital Elevation Models, Pit filling (preferred solution, check the DSM)
  • Rasters / Images, SEGMA, 1- Fill cavities
4) Apply a gaussian filter: Rasters / Images, SEGMA, 2- Gaussian filter. Check the pit filled image. Choose the filter strength. This parameter has a big impact on the results: try different values. The by default seems good in many cases.
5) Detect maxima: Rasters / Images, SEGMA, 3- Detect Maximum. Check the filtered image (gaussian).
6) Filter maxima: here you have two choices (in both select filtered image - gaussian):
  • Rasters / Images, SEGMA, 4- Filter maximum by exclusion radii (classical way). Provide a text file with two column: first column height, second column exclusion radius
  • Rasters / Images, Digital Elevation Models, Filter maxima by neighbourhood (experimental and not published way).

7) Apply a Watershed: Rasters / Images, SEGMA, 5- Watershed (flooding). Select filtered image (gaussian) and filtered maxima.
8) Apply the following step (pre-processing for the next step): Rasters / Images, SEGMA, 6- Create rasters for each crown. Select Pits filled image and Watershed
9) Correct segmentation: Rasters / Images, SEGMA, 7- Analyze/Crop crowns. Check IDCluster and watershed. This step has not been completely tested in its Computree version but seems to give intended results.
10) If you want to extract points clouds by crown, apply: Rasters / Images, SEGMA, 8- Extract points for each crown (v2). Check first results. For the first one check scene. For the second check Isolated cluters / Isolated cluters / IDCluster AND Modified clusters.
11) Export the segmented raster: Export, Rasters / Images, GDAL Geotiff for example. Check modified clusters.

I hope it helps.
Best regards.
Alexandre Piboule.

RE: Is there any documentation... - Added by Piboule Alexandre over 5 years ago

Hello again,

An important point: SEGMA is the Computree version of the SEGMA algorithms created by Benoît Saint-Onge of the Université du Québec à Montréal.
In the future version of Computree, citations for each plugin/step will be given.

Best regards.
Alexandre Piboule.