Exercise 2: Lava Detection using Supervised Classification - continued


Page123

 
Training fields

  • Choose an RGB band combination (e.g. 4-5-3) and stretch the image so that you can visually distinguish between different classes.
  • Multivariate Analysis >Supervised Classification > Select Training Fields or press on the red TF icon. A new bar will open.
  • Press the open icon in TF bar
  • Open the file TF_2001_6cl.sav
  • Inspect some of the training fields and look at the classes.

 
 
 
Training fields for Landsat 2001 (FCC 4-5-3), 6 classes
 
To learn how to work with the GIS module, please refer to the tutorial on p. 92.

To draw some more training fields:

  • Digitise an area.
  • Finish the polygon with a right click on the mouse.
  • In the training fields window name the polygon according to the class and then press enter.
  • Save the result (the icon is in the TF bar).


 
 
 Running the classification, assigning colours to classes

  • Open the un-stretched (original) Landsat 2001 bands number 1, 2, 3, 4, 5, and 7 separately as greyscale images.
  • Mark the FCC where you have opened the training fields before.
  • Go to Multivariate Analysis >Supervised Classification > Maximum Likelihood.
  • Pressing the shift button, mark the un-stretched band number 1, 2, 3, 4, 5, and 7 of Landsat 2001.
  • Set the threshold to 0 (zero) so that all pixels get classified
  • Press OK
  • The process will now run for several seconds to one minute, depending on the image size, the number of bands, and your computer.

 
 
Page123

 
 
  
Last update: 17 April 2013


Nyiragongo and Nyamuragira

 •  Introduction (http://www.esa.int/SPECIALS/Eduspace_Disasters_EN/SEMDGLNSNNG_0.html)

Change detection and hazard assessment

 •  Worksheet introduction (http://www.esa.int/SPECIALS/Eduspace_Disasters_EN/SEM5NUMSNNG_0.html)
 •  Exercise 1: Exploring and learning about the volcano (http://www.esa.int/SPECIALS/Eduspace_Disasters_EN/SEMV2MNSNNG_0.html)
 •  Exercise 2: Lava Detection using Supervised Classification (http://www.esa.int/SPECIALS/Eduspace_Disasters_EN/SEM1LSNSNNG_0.html)
 •  Exercise 3: Multitemporal Change Detection and Monitoring (http://www.esa.int/SPECIALS/Eduspace_Disasters_EN/SEM8XTNSNNG_0.html)

Eduspace - Download

 •  Nyiragongo_Landsat.zip (http://esamultimedia.esa.int/docs/eduspace/Volcanoes_Exercise_Data_3.zip)

Eduspace - Software

 •  LEOWorks 3 (http://esamultimedia.esa.int/multimedia/LEOWorks3.exe)
 •  LEOWorks 3 Tutorial (http://esamultimedia.esa.int/multimedia/eduspace/leoworks3-tutorial.pdf)