On our ever-changing Earth, conditions may change quickly or slowly. Some changes come from natural processes; some from human activity. Satellites allow us to see conditions and track changes over time — in land use, forest health, land/water interface, and so on. Since 1972, Landsat satellites have been collecting data using various portions of the visible and invisible electromagnetic spectrum, at a scale close enough to see highways, but not individual buildings on a city block.
Today, people are “mapping our world” with the aid of Geographic Information Systems (GIS) technology. Mapping can be done in the field or the lab—even from smartphones. You can make maps with real-time data about wildfires, tsunamis, and tornadoes. You can make maps with imagery collected with visible light, infrared, and radar data.