What is infrared imagery useful for?

You may notice that most visible imagery products (red, blue and green colours) are augmented by a near infrared channel

Most of our clients are interested in visible imagery, which is intuitive to interpret by the non-expert. For many applications, it is worth also considering the value of infrared imagery. While not as easy to interpret as natural colour imagery, it does have distinct value, particularly in relation to the condition of ground conditions including vegetation. As it happens, near infrared (or NIR, just beyond red in the electromagnetic spectrum), is very often available with natural colour imagery, at no extra cost. NIR imagery is sensitive to such conditions as plant stress and photosynthetic activity, and so is useful to any application where the condition of vegetation is of interest, either directly or indirectly, and can be used along with natural colour bands to create “false colour imagery” to map such conditions as vegetation stress over an area. In the example below, a map has been created of "Normalised Difference Vegetation index", or NDVI, which is a standardized way to measure healthy vegetation cover, and it makes use of red and NIR channels.


NDVI map from NIR and red channels for the USA, showing areas of abundant healthy vegetation in green (false colour image).

NIR imagery, like visible imagery, is impacted by cloud cover and sensitive to daylight. Short-wave infrared (SWIR), is only available from a small number of satellites at present, but has the advantage of not only being able to be used during dawn/dusk, but also being able to “see” through light cloud (such as mist), haze and smoke. SWIR is sensitive to vegetation conditions, ground cover and soil moisture. Its value in penetrating smoke and haze made it invaluable in providing regular updates on the California wildfire situation this summer as it could see the conditions of the ground beneath (see here). Further along the electromagnetic spectrum is mid and long wave infrared which is sensitive to temperature, and hence useful for relative differences in surface temperature such as currents, fires and heat emissions, and water cover vs land cover. At these wavelengths, sensors are measuring energy from the Earth and not the Sun and so do not depend on daylight.

Contact us for more information on how you might be able to incorporate infrared imagery into your activities.