The basic principle of imaging radars is to emit electromagnetic radiation towards the Earth surface and to record the quantity and time delay of energy backscattered.
This information is carried by the electromagnetic waves defined by:
- direction of propagation
The relation between frequency f and wavelength l can be shown as:
f = c/l
For microwave remote sensing, the used wavelengths are usually between 1 centimetre and 1 metre. The figure presents the electromagnetic spectrum and the letter designations of the microwave portions commonly used.