US: Farmers are using maps created with free data from NASA and the US Geological Survey”s (USGS) Landsat satellites that show locations that are good and not good for growing crops. Farmers like Gary Wagner rely on zone maps compiled with data from remote-sensing instruments including NASA and the USGS”s Landsat satellites. In addition to telling him about the state of his fields, remote sensing is invaluable if he decides to obtain a new piece of land, say from another farmer who decides to retire.
As a potential buyer, he can look at historical data, going back over three, four, or five years of remote sensing images to see the variability in the field and know exactly where he needs to make changes or improvements before he ever starts farming that field. And that”s critical, says Wagner, because otherwise, such as in his father”s day, he”d have to farm that field three or four years before he”d really know what”s going on there. With remote sensing data sets, he can understand that field before the very first time he puts his tractor in it. If he needed to, Wagner could go back and find data for his fields at least every year within the 40-year archive of Landsat data managed by the US Geological Survey.
Wagner”s map—a special kind of map known as a zone map—shows the difference between healthy and stressed plants by representing the amount of light they”re reflecting in different bands of the electromagnetic spectrum. To display this information on his map, the visible colors of light—red, green, and blue—are each assigned to a different band. Red, for example, is assigned to the near-infrared band that isn”t visible to humans. Healthy leaves strongly reflect the invisible, near-infrared energy. Therefore green, lush sugar beets pop out in bright red on Wagner”s map while the yellow-leaved stressed plants appear as a duller red. Wagner can use this map to track and document changes in his crop’s condition throughout the season and between seasons. As a tool, this map supports and enhances his on-the-ground crop analysis with independent and scientific observations from space.