Is one from the information science, computer science, modern geography, mapping remote sensing science, space science, environmental science and management science and many other subjects formed a new integrated discipline, the core of computer science, basic technology is the database, maps can visualization and spatial analysis techniques. Simply put, GIS is the deal with geographic data (information) input, output management, query, analysis and decision support computer system.
1 Overview Foreign trade that the widely used since the 19th century maps and thematic maps can be considered a simulation of geographic information systems. According to this definition, the generation of GIS geographical map can be traced back to Song Dynasty Stele, which the mountain carving, the Yangtze River, Yellow River, the Great Wall and the administrative bodies at all levels, is the Song Dynasty map of China.
Geographic Information System "geographical" concept does not refer to the traditional geography, but broadly refers to the geographical coordinate reference system of coordinates (spatial) data, attribute data and applications on this basis technology.
1963, the Canadian scientist RFTomlinson measure first proposed the term of geographic information, he said that "the map into a digital form of maps, so that the computer analysis and processing" of the new concept, and began a the use of computer technology to set a precedent for geospatial data. In 1971 he presided over the establishment of the world's first GIS??? Canada Geographic Information System (CGIS), for natural resource management and Planning .
Spatial position, attributes and time is of the three basic elements of GIS. Both spatial characteristics of geographic information, there are a variety of attributes, and change over time, with the massive amount of data. Such as car navigation systems, and navigation-related information such as urban construction, road building, road conditions change with time are. In addition, the system should be included with the navigation map attractions, supermarkets, Gas station , Restaurants, hotels, car parks and other spatial attributes for users of inquiry, and these attributes change over time in tandem.
Since ancient times, almost all human activities are occurring on earth, with the location of the earth's surface (ie, geo-spatial location) are closely related, with the increasing development of computer technology and popularization of geographic information systems, and on this basis developed on the "Digital Earth", "Digital City" in people's production and life will play an increasingly important role.
2 GIS in research content 2.1 Input Geographic data (information) to enter into GIS is a costly, time-consuming task. Most GIS geographical data from paper maps, commonly used method is to digitize and scan. The main problem is that the number of low efficiency and high cost; scan input is faced with another problem, the scanned raster data into a GIS database, how to transform usually requires a point, line, surface, topology and other forms of property, on the field are of research, the intelligent automatic map does not identify the short term may be achieved. Thus, the interactive map is a vector-based method of identifying a more realistic way, the market has a variety of interactive vector-based software for sale.
Input current GIS are increasingly using non-map form, a form of remote sensing is one. Remote sensing data, GIS has become an important source of data, and map data of different remote sensing data into GIS is relatively easy, but if by the interpretation of remote sensing images to collect and compile geographic information is a more difficult task. Therefore, GIS integration in large quantities in Image Processing Technology, many mature GIS products, such as MAPGIS has featured in the image processing subsystem.
Geographic data acquisition is another major progress GPS Technology. GPS can accurately and quickly determine the location of persons or things in the Earth's surface, Thus, in addition, as the sources of the original GIS, GPS vehicle tracking, emergency management, environmental and resources monitoring and management, has great potential.
2.2 Storage GIS data into raster data in (X, Y) and vector data (longitude and latitude) two categories, how to efficiently store and manage computer data is a GIS these two basic problems. Today, the rapid development of the computer, although microcomputer Hard disk Capacity has reached the GB level, but the computer's memory for flexible, efficient handling of such objects is still the map is not enough. GIS data storage has its unique features, most of the GIS system using a hierarchical technique that, according to some features of the map, it is divided into several layers (such as roads layer, attractions layer, layer of public facilities, etc.), the whole overlay a map of all the results. In the process of interaction with the user to only deal with the layer, rather than the whole site maps, user requirements and thus be able to respond quickly.
2.3 the operation and analysis of geographic data
GIS data in the operation provides a means for the effective management of geographic data. Graphics data (points, lines, surfaces) and attribute data to add, delete, modify, most can learn the basic operation of CAD and General The mature technology of the database; be different is that GIS spatial data and attribute data (such as attractions, the hotel guest Rates Georgia, etc.) close together to form a description of the surface features. Problem is that one type of data is bound to affect the operation of another related data, which operate to bring the data consistency and operational efficiency of GIS data manipulation is still a major problem.
Geographical data analysis functions, namely, spatial analysis, GIS can be widely used is an important reason. Provided by GIS spatial data analysis capabilities, users can draw a known geographic data implied an important conclusion, which for many applications (such as business location, disaster relief, etc.) is essential.
GIS output is the result of user queries or data analysis of the results as text, graphics, multimedia, virtual reality and other forms of output, is the GIS problem-solving process is the last process. Output Type There are usually two: the computer screen or through the plotter output. For some of the output application field of high precision, high-quality output capabilities of the GIS is essential. These technologies include: data correction, editing, graphics modification, error elimination, coordinate transformation, publishing Print Etc.