For example, healthy green leaves are excellent reflectors of near-infrared wavelengths. The thematic mapper's fourth band detects reflected energy in this range, so it is particularly useful for identifying and mapping vegetation in a given area. Data from the thematic mapper are transmitted to stations on the ground. By international agreements, this information must be made available to anyone who requests it. It comes at a cost, however.
Discounts are available for bulk purchases or for older inventory.
A GIS is a computerized storage, processing and retrieval system with hardware and software specifically designed to cope with geographically referenced spatial data and the corresponding attribute information - that is, maps that illustrate topography, water availability, population densities, administrative boundaries and transportation, energy and communication lines. A GIS allows information from these different maps to be combined and manipulated to meet a broad range of planning needs. This 'overlaying' function is one of the the most important tools of GIS, together with modelling and site selection for specific tasks.