Satellites and Forests

The View From Above
Unless there is human intervention, trees don't leave their original locations. It is this tendency to stay in one place that makes forests ideal for monitoring, tracking and analyzing from the air and outer space.

Plane Thinking
Forest aerial reconnaissance began with the invention of the airplane. The plane would haul a camera aloft to take simple black and white pictures. Over the years, the methods have become much more sophisticated. Through a process called "photogrammetry", technicians now combine two aerial photographs taken simultaneously to produce a 3-D image, thus yielding a highly detailed map of forest cover.

Remote Control
When satellites were first launched by the Soviet Union and the United States in the late 1950s, it was their capability for military surveillance that preoccupied the space race. But it wasn't long before satellites were employed for remote sensing of land use. Today, one of the most valuable applications of satellite remote sensing is the ability to track changes in forest cover. With powerful lenses and the ability to see infrared and ultraviolet light, satellites can observe individual trees, determine tree species and calculate the age of whole forests. Satellites are also used to spot forest fires, monitor forest harvesting, and chart forest health.

Satellite remote sensing offers the big picture of forest cover by region and even by nation. For example, satellites reveal that the area of forested land in the United States increased by nearly 10 million acres (3.9 million hectares) between 1990 and 2000. Satellites also reveal that Canada 's forest cover has remained unchanged during that same period.

Taking a Position
Like the Global Positioning System (GPS) used by hikers, boaters and drivers seeking directions, GPS systems are used to survey forest harvesting operations to make sure they are carried out within boundaries.

The United States and Canada share 15 percent of the world's total forest cover. They are also the world's top two forest product producing countries. Aerial and satellite imagery confirms that timber harvesting doesn't have to mean the loss of forested land.