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Taking a closer look at digital satellite images


Living in a visual age of digital cameras, smart phones and internet, digital images have become an essential part of our everyday lives. But how are digital images set up and structured, and what kind of information do they contain? The learning module “Contrast” explores these questions and explains the way an image is made up of single pixels and how the computer stores information conveyed via these pixels. In doing so, the pupils can deduce from the binary numeral system how the computer saves information in bits and bytes. What is more, they can figure out how these numbers – consisting of 1s and 0s – are becoming visible as well as interpretable for us human beings in the form of an image. Thus, this learning module conveys important basic knowledge of remote sensing. A somewhat defective digital aerial image, which is to be corrected by the pupils, is central to the module.

Digital photography developed in the context of space travel and earth observation and has been in use since the 1970s. Evidently, dropping a roll of film with re-entry capsules – a technique that had been common until the 1960s – was too inconvenient indeed.

Time required
2 lessons
3: extending
Recommended Prior Knowledge



Roland Goetzke

Henryk Hodam


binary numbers
bit & byte
digital images


The pupils ought to be able to describe and explain the set-up of satellite images.

They will be able to apply the binary numeral system and translate binary numbers into decimal numbers.

Ability to name the value range of 8 bit.

Manipulation of grey scale values of a digital image through the modification of grey values of single pixels and through a histogram stretch.

The pupils ought to be able to explain a histogram.