Geographic information systems (GIS) are a specialized category of information systems, in which data and information have an explicit spatial component given by location. A GIS comprises data, software, hardware, people, and operational procedures. GIS does not exist in a vacuum, it is always a part of a larger information infrastructure, where it fulfills specific functions aimed at responding to users’ information needs. The users of geographic information involve public organizations, such as local, regional, and national governments; private companies; and individual members of the public. Since much of the information generated by GIS is used to support decision making, GIS have been sometimes referred to as spatial decision support systems. GIS share a core set of functions enabling spatial data input, storage, editing and ...