Talk:Region Growing Segmentation

Region Growing Segementation with Saga's Seeded Region Growing Tool

The following tutorial explains how to delineate tree crowns, using SAGA's Seeded Region Growing Tool. The product, a polygon shapefile, can then be used in an object based classification, f.ex. in order to classify different tree species.

Material you need to complete the tutorial:

Data

An orthophoto, or a satellite image (preferably with different spectral bands) A canopy height model CHM

Software

QGIS 2.18.11 SAGA 2.3.2

Seed points

The first step here is to extract the position of the tree tops, which are going to be the starting point for the region growing algorithm. You find a descritpion how to derive the seed points from a CHM [[1]].

Now have a look at how the seeds align with your surface picture (orthophoto or else):

[[2]] 300px

In this picture you see, that the points align well with the tree tops, but there are many points that represent small trees in the lower left corner which you might not be so interested in. In order to correct that, we are going to filter the points by their height in the seed shapefile and save the shapefile with the selected seeds only (save as....)

This looks much better:

[[3]]

File:Filtered seed points.png

Filteres seed points