Samuel Goward, Professor Emeritus in the Department of Geographical Sciences at the University of Maryland, has been working with Landsat data since the program’s start in the 1970s. He points out just how revolutionary the shift from visual to computer-based data analysis was. “With the scanners you now have measurements of physical phenomena rather than a picture,” he says. “You can then convert each pixel into a biophysical measurement of what’s going on in that location.”
This was not simply a technological advance — it changed the way researchers thought about the planet. For Goward, Landsat meant “a new science of looking at planet Earth.”
Previously, in the laboratory, scientists tended to focus on discrete phenomena: individual cells, even particular molecules. With aerial photography, too, they could only identify what was or was not there — determining, say, that a tree once stood in the spot where a building now sits.
The digital sensors used by Landsat, though, make it possible to look at phenomena that are continuously variable over space and time, such as levels of photosynthesis. “I think learning that we could measure photosynthetic activity on the planet was as startling as anything to me,” Goward recalls. “It flipped the paradigm.”
Healthy plants with a high concentration of photosynthetic pigments bounce back high levels of near-infrared energy; as the plants sicken, their reflectivity decreases. Say you want to map how forests recover after wildfires or track the distribution of controlled burns across farmland. Landsat is the satellite for you.