A term currently in circulation among marine biologists, environmental hazard assessors, and others who rely on satellite data to find things out about our planet. Many of the satellites they use have been in orbit--either geostationary or whipping around the globe every ninety minutes--for decades, and the info they send back is steady and reliable, but the incurable curiosity of scientists requires that it be verified.

Thus, these guys and gals see a pattern that's remarkable and dispatch a human being or a team of them to test soil/water samples at the exact point of interest at the exact time the satellite in question is beaming back info. This practice is called "ground truthing." (They use it as a verb.)

As one molecular biologist I know put it, "You've got the satellite up there scanning the ocean, you've got a NASA plane with a facsimile of the same sensor scanning the ocean, and you've got a guy with a cigarette hanging out of his mouth dipping a bucket into the ocean at the same time. Isn't the technology supposed to take care of this?"

Well, it is. But to ground truth the technology is, I think, a sound practice. Relying solely on what satellites tell us is bad science, I would say. Use them to find patterns worth exploring, but for Newton's sake, send a person to observe them before you draw conclusions that are supposed to be meaningful to people.

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