地理信息系统(英文)教案

地理信息系统(英文)教案内容摘要：

determine the length of each hole, which then provides us with the total course length (which is an important 5 consideration for any golfer). Furthermore, based on a determination of the area of the holes, we can even begin to be able to calculate our needs for grass seed and fertilizer. Overall, this process has involved a number of key steps. Several different kinds of spatial data were located, and then manipulated so that the important features in each were found at the same locations. Once these data were brought into a mon geographic or spatial referencing system, it was possible to use them together, to develop a variety of types of derived information: the determination of potential corridors on the site, proposed locations for constructing facilities, and eventually, engineering estimates for earth moving equipment operators. As we will see, this is a very typical flow of data and information through a spatial data processing and analysis problem. Applications The number of data layers one needs to consider varies greatly from one application to another. Consider a more plex problem: deciding on the location of an airport. Some of the data layers or themes that a planner might require to site an airport include: Administrative Infrastructure Land Ownership Transportation Network Government Jurisdiction Utility Corridors RightsofWay Zoning Restrictions Mining Claims Existing and Use Biotic Endangered Species Abiotic Vegetation Cover Surface Geology Subsurface Geology Climatic Surface Water Temperature Subsurface Water Precipitation Flood Plains Fog Archaeological Sites Wind Elevation Photoperiod Geographic information systems are used in a wide variety of settings. Landscape architects have embraced the concepts behind GISs for many years, analyzing site suitability and developing capabilities of planning for a specified use (McHarg, 1969). Civil engineers and architects involved in developing large sites have parable interests and techniques, including considerations of environmental impacts such as noise perception and obscuring or changing views. Forestry professionals use this technology for site mapping and management, and for pest and disease monitoring. City planners are using geographic information systems to help automate tax assessment, emergency vehicle routing, and maintenance of 6 transportation facilities and public lands. Environmental managers and scientists use these systems for such applications as maintaining an inventory of rare and endangered species and their habitats, and monitoring hazardous waste sites. In addition to these kinds of applications, military planners add several more: gauging the ability of heavy vehicles to traverse different kinds of terrain, and determining which sites on military bases which are suitable for various kinds of training exercises. We discuss in more detail a few of these varied kinds of applications in Chapter 12. Geographical Concepts Before proceeding further, we will introduce a number of terms in mon usage (based in part on the brief discussion in Van Roessel, 1987). We will return to some of these in more detail in chapter 3. Spatial objects are delimited geographic areas, with a number of different kinds of associated attributes or characteristics. The golf course discussed above is a spatial object: it is a specific area on the ground, with many distinct characteristics (such as land use, tax rate, types of vegetation, number of parking spaces, etc.). On the golf course are a number of other spatial objects, such as the greens and fairways. A point is a spatial object with no area. The holes on our golf course represent points, even though they do in actuality cover a finite area. One of the key attributes of a point are its geodetic location, often represented as a pair of numbers (such as latitudelongitude, or northingeasting). There may be a range of data associated with a point, depending on the application. In our example, we may wish to record the number of the hole, as well as the date when a given hole on our golf course was placed on the green. The latter is useful so that we may remember to move the hole periodically to minimize wear on the green. A line is a spatial object, made up of a connected sequence of points. Lines have no width, and thus, a specified location must be on one side of the line or the other, but never on the line itself. One important line in our example might indicate the outofbounds line between holes. Attributes we could attach to that line include the numbers of the holes that the line separates, and whether the line is indicated on the course by markers of a certain color. Nodes are special kinds of points, usually indicating the junction between lines or the ends of line segments. A polygon is a closed area. Simple polygons are undivided areas, while plex polygons are divided into areas of different characteristics. Since our example golf course hole has interior objects, such as the sand trap and the green, it is a plex polygon。 since the sand trap is homogeneous (according to the available information in the figure), it is a simple polygon. Attached to the polygons on our golf course might be information about the length and area of each hole, and the kind and amount of seed and fertilizer used to maintain the fairways. Chains are special kinds of line segments, whi。