We've preliminarily chosen two sites for me to go visit actually maybe next week. I'm going to tell you how we chose those. But first I want to talk to you about what remote sensing is. Remote sensing is the act of acquiring information about an object without our being in contact with that object. Information gathered by sensors that are placed on either aircraft--you saw an aerial photo earlier--or satellites, and this is a satellite image. Passive sensors placed on satellites are very analogous to cameras. These sensors digitally record naturally occurring electromagnetic images that are reflected by the earth. I felt that with physics this morning, I could go into the electromagnetic spectrum this afternoon.

Unlike human eyesight or conventional color cameras, which are limited to the visible spectrum right in here, passive sensors can record information from throughout the whole electromagnetic spectrum. Each land feature exhibits different spectral characteristics. Plainly put, different objects reflect different wavelengths of energy in varying but predictable amounts. The different spectral characteristics allow us to identify different features on the earth's surface, such as this shown here on the graph. You can see that the darker green line is trees; lighter green is grass, purple is soil and blue is water. And if you look right in this area here, you can clearly distinguish the signals from each of these different types of land cover.

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