Example


The following images show the different degrees of reflection at different wavelengths for glaciers on Svalbard. They depict how the satellite sensor sees the area in different wavelength sections.
 
  
 
True colour satellite image of Brøggerhalvøya, Svalbard, Norway
 
True colour satellite image of Brøggerhalvøya, Svalbard, Norway
 
 
 
The image of the red channel shows the reflection in the red par
 
The image of the red channel shows the reflection in the red part of the electromagnetic spectrum
 
 
 
Image of the Near InfraRed channel
 
Image of the Near InfraRed channel
 
 
 
Image of the ShortWave InfraRed channel
 
Image of the ShortWave InfraRed channel
 
 
 
Number of pixels with a certain reflection in the red, NIR and S
 
Number of pixels with a certain reflection in the red, NIR and SWIR channels
 
In sum, snow and ice have a very high reflection in visible wavelengths (white colour), decreased reflectance towards the NIR, and even lower values of reflectance at the SWIR. Snow and ice are thus nearly black in the SWIR, a type of radiation humans are not able to see with the naked eye.
 
 
 Questions
  

1. Fill in the following table by marking, for each snow/ice type, if its reflectance is high, medium or low in the VIS, NIR and SWIR regions of the spectrum. An example is given for snow in the VIS.

  Snow Firn Glacier
ice		 Dirty
glacier
ice
  VIS NIR SWIR VIS NIR SWIR VIS NIR SWIR VIS NIR SWIR
High
reflectance		 X                      
Medium
reflectance		                        
Low
reflectance		                        

2. Print out the above colour, VIS, NIR and SWIR images. Place a transparency on one of the four and try to outline some areas with snow, firn and ice. When you are finished, put the transparency on the other images and compare how you outline the areas on these.


 
 
  
Last update: 16 April 2013


Remote sensing of ice and snow

 •  Remote sensing of ice and snow (http://www.esa.int/SPECIALS/Eduspace_Global_EN/SEMWD7TWLUG_0.html)

Background

 •  Ice – a special substance (http://www.esa.int/SPECIALS/Eduspace_Global_EN/SEMHE7TWLUG_0.html)
 •  Optical properties of ice and snow (http://www.esa.int/SPECIALS/Eduspace_Global_EN/SEMPJ7TWLUG_0.html)

Exercises

 •  Introduction (http://www.esa.int/SPECIALS/Eduspace_Global_EN/SEMRFDTWLUG_0.html)
 •  Purpose of the exercise (http://www.esa.int/SPECIALS/Eduspace_Global_EN/SEM9IDTWLUG_0.html)
 •  Exercises (http://www.esa.int/SPECIALS/Eduspace_Global_EN/SEM7KDTWLUG_0.html)

Related link

 •  GlobGlacier Project (http://globglacier.ch/docs/dvd/index.html)