Unsupervised Classification and Polygonization With QGis
Contents
- 1 Video Walkthrough
- 2 Introduction
- 3 Programs and Plugins required
- 4 Acquiring Data
- 5 Unzipping Data
- 6 Importing and Displaying Data
- 7 Trim to Mask Area
- 8 Unsupervised Classification and Filtering
- 9 Polygonization (Raster to Vector Conversion)
- 10 Field Calculator
- 11 Editing and Merging
- 12 Map Production
- 13 Resources
Video Walkthrough
If you would like a video walkthrough please follow this link to youtube!
Introduction
There are lots of reasons for wanting to make a land cover classification. Whether that is to make beautiful maps, a temporal study of change or a more complicated statistical analysis. The goal of this tutorial is to be a jumping off point so to speak into the profound and complicated world of classifications.
In this tutorial we will be looking at how to perform an unsupervised classification; that is a classification where the computer program chooses the classes without a training data set
Programs and Plugins required
Qgis (3.22 was used in this tutorial) https://qgis.org/en/site/forusers/download.html
7Zip https://www.7-zip.org/
SCP Plugin (download through QGis)
Acquiring Data
For this tutorial pretty much any remote sensing data can be used. Depending on what data it it it may require pre-processing in order to produce a usable product, and that is outside the scope of this tutorial.
A good resource for free remote sensing data us the USGS Earth explorer. It involves making an account but it is such a good resource for remote sensing data that it is completely worth the extra step.
Sign up here https://ers.cr.usgs.gov/login
Now that you have made an account or signed into your existing account it is time to find the data to use.
