Exercise 1: Inspecting the images


Download the LEOWorks image processing and GIS software from the right menu. Open the three images (05102004.tif, 25102005.tif and 10102006.tif) separately. Now you have 3 greyscale images of the study area.
 
  
 
SAR image before (left) and after (right) filtering
 
SAR image before (left) and after (right) filtering
 
Due to the fact that SAR data are subject to speckle (a multiplicative random noise that considerably reduces the interpretability of the images), all ASAR images should be speckle reduced with the aid of a filter. Use a non-linear 3x3 mean filter and apply it to the three images you have opened. Save the new images as 05102004_f.tif, 25102005_f.tif and 10102006_f.tif respectively.
  
 
1. Observe the pre-flood images (05102004_f.tif, 25102005_f.tif). Taking into account everything you know about the interpretation of radar images, try to distinguish the following elements: lakes; villages; agricultural fields; roads.

2. Can you explain why the lake is not uniformly represented by a single backscatter value on each image, but its brightness varies from place to place? Why does the lake differ from one image to the other?

3. Now observe the post-flood image (10102006_f.tif). Can you find smooth surfaces that indicate the presence of water bodies besides Lake Volvi? Can you find any other changes by simultaneously observing the pre- and post-flood images?


 
 
  
Last update: 10 September 2013


Flash floods in Thessaloniki

 •  Introduction (http://www.esa.int/SPECIALS/Eduspace_Disasters_EN/SEMVPF826KH_0.html)
 •  Background (http://www.esa.int/SPECIALS/Eduspace_Disasters_EN/SEMVPG826KH_0.html)

Exercises

 •  Exercise 2: Change detection – band math (http://www.esa.int/SPECIALS/Eduspace_Disasters_EN/SEMQSG826KH_0.html)
 •  Exercise 3: Change detection – Multi-temporal analysis (http://www.esa.int/SPECIALS/Eduspace_Disasters_EN/SEMYTG826KH_0.html)
 •  Exercise 4: GIS (http://www.esa.int/SPECIALS/Eduspace_Disasters_EN/SEM58I826KH_0.html)

Eduspace - Software

 •  LEOWorks 4 (Linux) (http://leoworks.asrc.ro/download/leoworks.jar)
 •  LEOWorks 4 (Windows) (http://leoworks.asrc.ro/download/leoworks.exe)
 •  LEOWorks 4 (MacOS) (http://leoworks.asrc.ro/download/leoworks.app.zip)

Eduspace - Download

 •  Thessaloniki.zip (http://esamultimedia.esa.int/eduspace/Thessaloniki.zip)