#ColorChallenge: From Space, red is the color of vegetation!

Many satellite images have a fair amount of red in them. This is because the sensors they are equipped with are also sensitive to light in the near-infrared portion of the electromagnetic spectrum. As a result, land objects that emit a lot of light in this part of the spectrum will look very different to those that do not. Following an image processing where this information is added to the picture, these objects will appear red in the final image. What are these objects? Vegetation!

Here is a satellite image of Berlin, taken by the European Sentinel 2 satellite in 2015:

In images taken by optical remote sensing satellites carrying a Multispectral Instrument (MSI) farmland, forests, and grass-covered areas, turn red. As pavement and rooftops reflect no light in this part of the spectrum, it is very easy to distinguish between parts that are green and those that are not. This is highly useful for a number of reasons. In cities, urban planners want to monitor the state and evolution of green spaces in and around the city over time. This to ensure a healthy environment for citizens. It is also used to monitor the status and health of forests around the world, whilst also detecting deforestation and forest fires.

But why are plants red? Or rather, why do they emit more light in this part of the spectrum? Healthy vegetation will absorb blue and red-light energy to fuel photosynthesis and create chlorophyll. A plant with more chlorophyll will reflect more near-infrared energy than an unhealthy plant. Therefore, when you photograph a forest or an area filled with vegetation with an infrared camera it will have a red colour. And the greener and healthier the plant is, the redder it will normally be. Thus farmland, where vegetation is often more yellow than green, will often be seen as more orange-looking squares.

Below is another image, taken with a similar camera at the Yellowstone National Park from Mount Sheridan in Australia, demonstrating how trees appear as red.

source

Love these images? Follow me to receive more posts with unique images of our wonderful planet taken by satellites! In my new series, 5 Beautiful Satellite Images of our Planet you won’t believe are real, I show different parts of our planet as seen from a satellite.