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Landsat satellites have photographed every part of Minnesota every few days for fifty years, and the pictures are free. The state uses them to watch its cities spread, to check the clarity of more than 10,000 lakes, and to tell farmers how much fertiliser their fields actually need.
Watching the Twin Cities grow
About 54 percent of Minnesotans live in Minneapolis–St. Paul, and city authorities have to balance growth against the land around it. From orbit, Landsat measures what people do to a landscape: sprawl, how efficiently land is used, how much of it is paved over by roofs, roads and car parks, where urban heat islands form, and how growth relates to changing rainfall.
The Twin Cities in August 1986 (left) and August 2018 (right). USGS.
10,000 lakes, measured
Minnesota's lakes are too many to sample by boat. Researchers at the University of Minnesota used Landsat to classify the water clarity of more than 10,000 of them — information state and local authorities use to decide where to protect and where to clean up.
Coloured dissolved organic matter in Lake of the Woods. NASA.
Fertiliser by the field
Landsat helps farmers rotate livestock, check crop condition, and vary seed and fertiliser across a field. AWG Farms in Minnesota has watched the health of its sugar beets from Landsat since 1997; with GPS-guided variable-rate spreading, it saves 60 to 70 pounds of nitrogen per acre — money saved, and less fertiliser washing into rivers and groundwater.
Landsat in brief
| Running since | 1972 — the world's longest continuous record of Earth's land surface |
| Now in orbit | Landsat 8 and 9, together covering the land every 8 days |
| Cost to users | nothing; the USGS Earth Resources Observation and Science (EROS) Center distributes the data worldwide |
| Value to the US | $2.06 billion a year, by a 2017 USGS study — far more than it costs to build and run |
| Next | Landsat Next, being designed by NASA and the USGS |
It is the most widely used land-imaging source in federal civilian agencies, and local, state and Tribal governments use it too, for everyday decisions about land and water. Businesses build it into logistics, investment and farming tools; commercial imaging companies use it to calibrate their own. Like GPS and weather data, it has become infrastructure.
Sources
Written from Minnesota and Landsat, U.S. Geological Survey Fact Sheet 2020–3059, a work of the United States government in the public domain.
Licencia: CC0 1.0 (dominio público) · Adaptado de pubs.usgs.gov
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