Landsat data is collected via satellite. The satellite contains sensors which collect reflected and emitted energy across various wavelengths from Earth. These measurements are compared with field data to accurately identify what is covering a surface, anywhere in the world. In GIS, the remotely sensed data is converted to a raster format. On a map, each cell contains different information, meaning one may have snow data denoting an area is covered in snow. The next cell over may have data from pavement, denoting a roadway outlined in snow. On a bigger scale, the map shows many characteristics of a large landscape allowing for geographic analysis.
Landsat data and GIS allows for real-world analysis of an area. In the case of the Mount St. Helens eruption, the data gathered from the site over time shows the extent of the damage from the debris flow, the size of the area affected, and how the landscape rebounded over time. For example, a lake Northwest of the explosion had so much debris added to it, water was redirected and a new, smaller lake was added just North of the original’s location. Without the Landsat data, it would have taken years to gather the amount of accurate, and broad data from the field.
