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Remote Sensing
Remote sensing is the act of collecting data about an object without physically contacting the object. For example, scientists can determine the landscape (hills and valleys) of the ocean floor without walking on it. To do this they send out sound waves from a ship. The sound waves reflect off the ocean floor and travel back to the ship. The scientists examine the sound waves' echo to determine the landscape of the ocean floor below. This method of remote sensing is called SONAR (SOund NAvigation Ranging).

A similar method of remote sensing is called RADAR (RAdio Detection And Ranging). While SONAR uses the reflection of sound waves to remotely sense objects, RADAR relies on the reflection of electromagnetic waves. This technology is used to track the movement of many things in Earth's atmosphere including airplanes and precipitation (rain, snow, etc.).

Another form of remote sensing is satellite imagery. Some satellites take "pictures" of the amount of infrared and visible light Earth gives off or reflects. Scientists analyze these images to estimate things such as the pattern of vegetation or clouds covering the planet. Satellite images are an important tool used by scientists to keep track of what is going on around the world.

One use of satellite imagery is the analysis of the impacts of wildland fires. A Quicktime animation of several satellite images has been created to display landscape changes in Yellowstone National Park that resulted from the fires of 1988. The animation was built from Landsat 5 data provided by the EROS Data Center in Sioux Falls, SD. The images of the park display the changes that take place over an eleven-year period. Some of the images are labeled with the date on which they were taken. The other images are just transition images. They are "fades" from one dated frame to the next.

The first frame in the sequence is an image of the park on September 22, 1987. This is about one year before the fires. The next dated image in the sequence was taken on July 22, 1988. The fires had just begun at this time. The blue haze in the right side of this image is smoke. Note the minimal landscape change in Yellowstone between September 22, 1987 and July 22, 1988. The third dated image in the sequence was taken on October 2, 1988. The fires had just ended. The ash- and soot-darkened brown areas are those that were burned. The burned areas cover much of the image. The fourth dated image in the sequence was taken on September 14, 1990. This is two years after the Yellowstone fires of 1988. The burned areas still appear brown from ash. There is little to no vegetation in these areas. The bare soil shown in this image contrasts sharply with the green, forested areas. The last frame in the animation was taken on July 18, 1998. That was 10 years after the 1988 Yellowstone fires began. There was still little vegetation in the burned areas. However, some dry scrub vegetation can be seen in pink in this image. (Note: the pink hue of the scrub vegetation is how they appear in infrared light, it is not their true color.)


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