Remote sensing
Data acquisition
  The electromagnetical spectrum
  Digital images
  Coding the values
  Size of the pixels
  The secret of colours
  The sensors
  Getting into orbit
  Remote sensing images
  Additional data
Image processing
Digital images
Painting by number

A picture or image is a plane representation of a real object. Pictures are everywhere in our societies, e.g., drawings, paintings, photographs, and so on. Recently digital images have been flooding the field. These images are composed of very large numbers of very small dots whose colours (or intensities) are defined by figures (hence ‘digital’ from ‘digits’). These dots are called ‘pixels’, from the contraction of ‘picture elements’.