Red Leaves and Green Seas

In this multispectral image of Kumbunbur Creek in the Northwest Territories of Australia, is a solid lesson in why false colour composite schemes are so useful in remote sensing.

In multispectral images, the collected light extends beyond the visible spectrum. False colour composites can map those bands to any colours, but a very common mapping is to assign the near-infrared band to red, assign the true-colour red band to green, and assign the true-colour green band to blue.

Because crisp, healthy vegetation has a high reflectance in near-infrared, the result is to highlight vegetation in vivid crimson.

The colour mapping also brings out the difference in water clarity, with the high green band reflectance of clear waters showing up as a dark blue, the high red band reflection of sediments colours turbid water an eye-searing cyan. Clear water appears dark-bluish (higher green band reflectance), while turbid water appears cyan (higher red reflectance due to sediments) compared to clear water.

Bare soils, roads and buildings may appear in various shades of blue, yellow or grey, depending on their composition.

The Korea Multipurpose Satellite (Kompsat-2) is tasked with imaging natural catastrophes, collecting data for geographic information systems, and surveying natural resources.

Image credit: KARI/ESA.