What is remote sensing and how does it work?
The principle of remote sensing is relatively simple. When light is emitted onto a surface, some light is reflected (as electromagnetic radiation) and some is absorbed. The reflected light will be across the whole electromagnetic spectrum, which is far wider than we can see. The spectrum can be split into visible (blue, green and red) and invisible (near infrared, infrared and beyond) wavelengths. Each object (eg crop) has its unique reflectance spectrum and as a result different objects are seen in different ways. Cereal crops look green because they reflect the green light and absorb the other light wavelengths. They also reflect light more strongly from the infrared part of the spectrum. The human eye can’t detect this, but an infrared sensor can. These sensors have been developed specifically to measure crop reflectance at different levels, to help farmers target inputs more effectively. Broadly speaking, the near infrared wavelengths are a measure of the canopy size, while the vis
