Jeulin 545 017 Mode D'emploi page 8

Geology
Radiation meter
Ref :
545 017
Earth observation satellites (Spot, Landsat, Météosat) do not usually take photographs of the
Earth, but they measure the luminance (L) of the different overflown points using on-board
radiation meters. Luminance is measured in several spectral bands for each point. These
various measurements are sufficient to differentiate soils and plants on the Earth's surface.
The principle of these measurements can be materialised by moving the radiation meter at a
constant altitude over a collection of different objects and plants arranged in line, and
observing variations of luminance firstly in one spectral band and then in others during
several passes over the same zones.
These measurements obtained point by point as for satellites, model the principle of data
acquisition and can demonstrate that:
- it might be possible to differentiate objects that have the same response in one spectral
band, in other spectral bands;
- identical objects have identical spectral responses.
The use of the radiation meter is justified particularly in the Final high school year Scientific
class, in theme 2 of the Natural & Life Sciences specialty:
« Contemporary global challenges - Atmosphere, hydrosphere, climates: from the past to the
future ».
More precisely, the radiation meter is a means of characterising the nature or composition of
soils.
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