by Jon Campbell at directionsmag
Summary:Humans have been observing Earth for a very long time simply because the conditions of the Earth are basic to our survival and our prosperity. Even the most ancient written records are filled with accounts of great floods, famines, and earthquakes. When to plant and when to harvest, how to use precious water resources most effectively, and ways to avoid natural disasters are all age-old challenges that have encouraged Earth observation from the beginning of civilization. But now we observe from afar.
Observing Earth became more systematic as society became more complex. Long-term observations of Earth’s tides, weather averages, and prevailing winds enabled local sailing conditions to be forecast with increased confidence. Observations of stream water flow were — and still are — crucial to farmers and communities who depend on irrigated crops. During the 18th and 19th centuries, the world’s leading nations sent out extended expeditions in the name of science to observe the oceans, lands, plants, and animals of Earth’s most remote regions. Cook, Humboldt, and Darwin are famous names from this period of Earth observation.
The modern concept of Earth observation is the gathering of detailed information about the planet’s physical, chemical and biological systems by networks of in situ(“in place”) instruments on the ground (e.g. streamgages, seismometers, meteorological stations) and remote sensing technologies positioned in air or space (commonly, photography, radar, or lidar in aircraft; electromagnetic sensors in satellites).