We tend to think that the world around us exists in the colors we perceive based on the photo-receptors in our eyes responding most strongly to red, green, and blue light, and our brain combining those impulses in a particular way.  But consider an image through an infrared scanner or night vision goggles, and you get an example of how other wavelengths can be turned into a visible image.  Everyday, there are hundreds of satellites orbiting the earth, scanning the planet for purposes from reconnaissance, to weather, to climate monitoring, and the sensors they have on board are not limited to the constraints of our eyes.  Where we are used to seeing the world in three wavelengths (red, green, and blue) the MODIS instrument, for instance, records data in 36 wavelengths.  Of course, we cant see a picture in 36 colors (some of them not even within the visible range), and anyway, a computer screen or printer requires everything to be encoded as signals to red, green and blue pixels or ink cartridges.  But these extra wavelength bands can be used in algorithms to determine interesting details which are difficult to determine with the normal colors (e.g. whether a point that looks green to the naked eye is grass or forest), and can be used to generate captivating and informative images.

The practice of taking non standard wavelength bands and rendering them in red, green and blue is called a “False Color Image” (as opposed to a “True Color Image” like a normal digital photo)².  There are a number of types of false color images, depending on what you want to see in the image, but one popular method is to substitute near infrared for red, red for green, and green for blue.  This combination is useful for showing plant health and also highlighting vegetated areas against constructed areas and water.  In areas with abundant vegetation, this results in a very striking red image.

I really find the above false color image of the New River Valley (from the ASTER satellite) to be intriguing.  It shows much more clearly the various assets of our region which we love and cherish.  The lush forests of the mountain ridges are a deep, dark red contrasted against the lighter reds of our verdant farm lands.  Our towns stand out as silver specks in a sea of red connected by barely visible strands of road.  The ancient New River is a dark blue thread, pushing mountain ridges asunder as it meanders wherever it pleases.

Looking at this image,  I get a sense of place and of comfort.  This is where we live.  This is our home.  This is where our children will grow up and find their place in the world.  Worry as we might about the world around us, the most important things we can do are right here in this 60×60 km square.  We need to take care of it, and the land, water, air, and people within.

1. see http://earthobservatory.nasa.gov/Features/FalseColor/page6.php for more information
2. see http://earthobservatory.nasa.gov/Features/FalseColor/page6.php for more information