Individual Tree Detection (ITC)
From AWF-Wiki
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(→Filter the CHM derived from LiDAR data) |
(→Watershed segmentation) |
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=Watershed segmentation= | =Watershed segmentation= | ||
| + | * In the search engine of the Processing Toolbox, type {{typed|text=watershed}} and select '''Watershed segementation''' under Image Analysis of SAGA. | ||
| + | * Select the inverted and smoothed CHM raster data file as input Grid. | ||
| + | * The Output is {{button|text=Segment ID}} | ||
| + | * Select as Method the flow accumulation of {{button|text=Minima}} | ||
| + | * Seed points: enter name and path for a vector point output file. | ||
| + | * Click on {{button|text=Run}}. | ||
| + | [[File:Qgis_smooth_invert.png|300px]] | ||
| + | |||
=Extracting tree heights= | =Extracting tree heights= | ||
=Generate a seed grid= | =Generate a seed grid= | ||
Revision as of 23:41, 6 January 2018
Contents |
Filter the CHM derived from LiDAR data
We use a Canopy Height Model (CHM) derived from LiDAR data as decribed here to detect individual tree crowns. Two preprocessing steps prepare a watershed segmentation approach: (1) Gaussian filtering and (2) inversion of a CHM.
- In the search engine of the Processing Toolbox, type smooth and select Smoothing (gaussian) under Image filtering of the Orfeo Toolbox.
- Select the CHM raster data file in GeoTiff format as input layer.
- The smoothing type is gaussian.
- The circular structuring element has a radius of 2 pixels.
- Enter name and path for an output file.
- Click on Run.
Invert the CHM
Now the smoothed CHM will be inverted.
- In the search engine of the Processing Toolbox, type invert and select Invert grid under Raster tools of SAGA.
- Select the smoothed CHM raster data file from previous step as input layer.
- Enter name and path for an output file.
- Click on Run.
Watershed segmentation
- In the search engine of the Processing Toolbox, type watershed and select Watershed segementation under Image Analysis of SAGA.
- Select the inverted and smoothed CHM raster data file as input Grid.
- The Output is Segment ID
- Select as Method the flow accumulation of Minima
- Seed points: enter name and path for a vector point output file.
- Click on Run.
