Although the focus of this course is reflected sunlight, it is worth mentioning that satellite technology now also includes LiDAR - Light Detection and Ranging. Like radar (radio detection and ranging), LiDAR works by sending out a pulse - in this case of light - and measuring how long it takes the pulse to return. This is a form of active remote sensing, whilst relying on reflected sunlight is passive remote sensing. Lidar remote sensing is opening up new avenues of research, particularly in measuring forest canopy height and biomass (the amount of Carbon stored in trees), as it is a much more direct measurement – of canopy height – than most remote sensing observations we can typically make.

Relying on reflected sunlight, as we have seen previously for optical EO, is a passive form of remote sensing. LiDAR, like RADAR is an active form of remote sensing, where we generate the signal ourselves. The difference between LiDAR and RADAR is that LiDAR operates in the optical domain, with some instruments using visible red and green wavelengths, but more usually slightly longer wavelengths in the near infrared (NIR) around 800-1000nm and short-wave infrared (SWIR) around 1600nm. These longer wavelengths are not seen by the human eye, making it easier to design eye-safe LiDAR instruments in those parts of the EM spectrum.

Featured Educators:

• Dr Mathias Disney

With thanks to the Royal Botanic Gardens, Kew.

Don’t forget you can download the video, transcript and take any quizzes available with the links on the right.