GIS 课前预习提示.doc

Geographic Information System 1. What is a GIS? ⑴ The definition of a GIS ? ⑵ What functions can GIS realize? ⑶ Differences between GIS and other information systems 2. History of development ⑴ What is the example of 35000 years ago ? What’s the common feature between early records and modern GIS ? ⑵ Example of John Snows 1854 map ⑶ first true operational GIS — CGIS used for what ? what capabilities ? ⑷ Development of CGIS/GIS in 20th century 3. What makes up a GIS? ⑴ Key components and their functions: ⑵ GIS Layer: 4. Techniques used in GIS 4.1 Relating information from different sources ⑴ Analyses: use information from many different sources in many different forms ⑵ Primary requirement： knowing the locations for the variables ⑶ convert existing digital information 4.2 Data representation ⑴ Real world objects : two abstractions discrete objects continuous fields ⑵ two methods to store data : Raster Vector ⑶ the characteristics of Raster data ⑷ the characteristics of Vector data ⑸ advantages and disadvantages： raster data model vector data model ⑹ non-spatial data stored： In vector data： In raster data： 4.3 Data capture ⑴ Data on paper or mylar maps: digitizer and Scanning ⑵ Survey data : survey instruments , GPS, another survey tool ⑶ Remotely sensed data : Sensors — cameras, digital scanners and LIDAR； Platforms — aircraft and satellites. passively measure / active sensor ⑷ aerial photographs：Soft copy workstations； digitize features from stereo pairs of digital photographs ⑸ relative accuracy or absolute accuracy ⑹ attribute data ⑺ editing ： remove errors，further processing Examples：undershoots – overshoots ， blemishes 4.4 Data manipulation ⑴ Data restructuring ：convert data into different formats. ⑵ convert structure : data sources may not be compatible— convert from one structure to another. 4.5 Projections, coordin