GIS is a computer system that solves problems related to spatial/geographic coordinates. It is built around specific data, which forms the core of the GIS system. The data model of GIS consists of both vector and raster data. Through this data model and advanced computer technology, the system can draw all key elements and symbols on various kinds of map. Besides, it can also simulate terrains and can therefore be considered a form of virtual reality technology as well. Although GIS can be used in many areas, such as cartography, environmental protection, city planning, communication, transportation and the like, its main application remains in spatial analysis, which can help solve many problems. Its objective is to provide a spatial framework that facilitates the making of strategic decisions regarding the optimal use of global resources and the management of our environment for sustainable development.
The essential data of the GIS system comes from various sources, including digitization of existing maps, remote-sensing images, survey data, digitized information and written reports. The acquired data are incorporated into the database after necessary pre-processing steps like analysis and selection. It should be noted that the quality criteria for the data of the GIS system can be classified into micro-criteria and macro-criteria. Micro-criteria are those related to homing precision, attribute precision, logical consistency and resolution of the data, while macro-criteria refer to their integrity, timeliness and regionality.