Remote Sensing and Environmental Monitoring

Remotely sensed data have two significant characteristics. Firstly, they are available in digital form, which allows them to be manipulated by computer. Secondly, they provide a range of information derived from observations made using electromagnetic radiation (EMR) with wavelengths ranging from those of the visible wavebands (0.4–0.7 μm) to the microwave region (3–30 cm). Modulation of incoming EMR by the atmosphere or land/sea surface provides information about the characteristics of these land, ice, and ocean surfaces and of the atmosphere. For example, observations in the visible and near-infrared regions of the spectrum are used to estimate “colour” (e.g. produced by the presence of phytoplankton in ocean surface waters). Thermal infrared and microwave measurements are used to monitor surface temperature and roughness/soil moisture characteristics, respectively. Overlapping (stereo) images in the visible and microwave wavebands are also used to derive digital datasets showing surface elevation using photogrammetric and interferometric techniques, respectively. Products such as maps of slope angle and aspect can be derived from these datasets.