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[ rain, thunder ]

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[ thunder, music ]

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[ bugs buzzing ]
If we measure the Earth from the ground, we

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can a get a good local picture of what is going around us.

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But if we want to measure larger portions of the Earth, then we'll need to use

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remote sensing. Remote

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sensing measures the Earth and its features without making physical contact.

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We can gather data from entire continents over longer time

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periods so we can look at how the Earth is changing.

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NASA uses specialized aircraft and sophisticated satellites to gather

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data using both passive and active remote sensing methods.

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Passive remote sensing measures the natural energy, or radiation, of the 

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Earth. Active remote sensing gathers data by actively sending

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out signals that interact with the target of interest.

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Using both active and passive remote sensing techniques, NASA can look at

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soil moisture maps to monitor drought, estimate

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snowpack in areas where snow is crucial for freshwater,

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measure the change in ice sheets and sea level, tracking

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storms that could impact human lives, and observing how

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precipitation changes affect where we get our freshwater. The Global

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Precipitation Measurement mission helps fill in the gaps where ground measurement

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isn't enough. Places with rugged terrain can block the signals from ground

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radars. The oceans are too vast to cover with enough

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ships and measurement stations on the surface, and places

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without the network of instruments needed to measure freshwater for people and agriculture.

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We can then unify the measurements to create a consistent and

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accurate picture no matter where we are. Because satellites get

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more complete coverage than ground-based instruments, we can use remote sensing

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to better see how the whole Earth is changing over time.

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With a long data record we can make better predictions about the water cycle, the climate,

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and the impact on humans.
[ wind, thunder, rain ]

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[ wind, debris flying ]

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[ tree splitting, insects swarming ]

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[ debris falling, bubbling, airplanes ]

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[ music ]

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By observing our Earth from above, we get a much better understanding of what is happening

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on the surface, in the atmosphere,

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underground, over the globe, and in our own

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backyard.
[ music ]

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