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When we investigate land cover using the instruments aboard

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Landsat satellites, we collect sets of data for different wavelengths.

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Some are in the infrared, and others correspond to blue, green, and

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red visible light. We can combine any three of the images

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to create different depictions of Earth's surface.

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What you're seeing now is a Landsat image of Florida,

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made with data from the blue, green, and red visible wavelengths.

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We call this a "natural-color" image, because it looks

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approximately what we would see with our naked eye, if we flew far above Florida.

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But we could choose data

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from other wavelengths, and map them to blue, green, and red colors

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to highlight different features of the land surface.

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With this particular depiction of the multi-spectral data,

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for example, we can see much greater contrast between trees & shrubs and

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sawgrass marsh, than was apparent in the natural-color image.

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We call certain combinations of wavelengths "false-color" images,

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because they do not replicate what we see with the naked eye.

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Yet they allow us to create images where we can highlight or enhance different surface features.

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The following depiction approximates the type of

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image that you can get from color-infrared film.

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It turns out that vegetation -

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growing, active vegetation - reflects a lot of light in the near-infrared

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and so areas with healthy, growing vegetation

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jump out as red in these images.

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You can easily distinguish the healthy agriculture more clearly

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than you can in the true-color image.

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Here you can look at the three different depictions of the

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multi-spectral data we use to create these images

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and you can see how the surface cover appears different with some features

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enhanced in the different depictions.

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