Hyperspectral sensors carried by satellites can document up to 490 different wavelengths of sunlight (400 to 2500 nanometres) reflecting off the Earth’s surface. The sensors generate in-depth, spectrally layered data packages. Together, these stacks of spectral images reveal objects and data that cannot be picked up by multispectral sensors—sensors that record far fewer spectra or combine ranges of visible, near-infrared and infrared wavelengths into far fewer spectral bands.
Hyperspectral imagery has been used to map mineral deposits and geology in Canada’s north. Canadian Forest Service researchers are now developing ways to use it in forestry.
Each type of ground cover—often each species of ground cover—absorbs and reflects a specific combination of wavelengths. If these are identified, validated and made available, they could be used to improve forest inventory and health information, as well as increase information about biodiversity, natural disturbances and the effects of climate change in Canada’s forests.
For example, Natural Resources Canada researchers and their colleagues have used imagery recorded by a satellite orbiting 700 kilometres above the Earth to map five individual tree species growing along British Columbia’s coast. The researchers also used similar airborne imagery to map chlorophyll, water content, and nitrogen levels within west coast forest canopies’ leaves.
In the future, by comparing mapped leaf nitrogen, chlorophyll or water content against known profiles of normal chemistry for species, researchers may be able to pinpoint stands of highly stressed trees. Forest managers could then go and look at what is causing the stress—disease, insects, drought or other issues—on the ground.
Canada contains 10 percent of the world’s forest, and is required to report on its forests. Hyperspectral imagery may eventually contribute to Canada's reporting commitments by providing forest managers information not available from other sensors.