It is very simple to use the GIS to identify the wells that are on conservation land. As an example, suppose we have a GIS data layer composed of conservation land in a region represented as polygons and another layer containing the location of preexisting water wells as points within the region (Figure 2). A polygon identifies an area, the last type of spatial object.īy defining spatial objects in this way, computer-based geographic information systems allow easy manipulation of the objects and permit many different types of operations to compare objects and generate new objects. A series of connected lines that form a closed chain is a polygon. Lines connect to other lines when they share a common node. This allows information to be attached to each side-for example, labels for land on one side and water on the other. If the line has a direction, then its two sides can be distinguished. If the two nodes marking the ends of the line are differentiated as starting and ending, then the line has a direction. Normally a line is straight, but it can also be defined as a smooth curve having a certain shape. These special points are often referred to as nodes. A line is also a spatial object with no area, but it has two points associated with it, one for each end of the line. Some spatial objects are illustrated in Figure 1.įigure 1: Spatial objects in a GIS can include points, lines of various types, intersecting lines, and polygons.Ī point is a spatial object without an area, only a location. This information may be as simple as a place name or as complicated as a large data table with many types of information. A spatial object is a geographic point, line, or area to which some information is attached. Geographic information systems are designed to manipulate spatial objects. SPATIAL OBJECTS IN GEOGRAPHIC INFORMATION SYSTEMS Geographic information systems have allowed geographers, geologists, geophysicists, ecologists, planners, landscape architects, and others to develop applications of spatial data processing ranging from planning land subdivisions on the fringes of suburbia to monitoring the deforestation of the Amazon Basin. A GIS is a computer-based system for acquiring, processing, storing, querying, creating, analyzing, and displaying spatial data. Recent advances in computing capability have enabled geographers to develop a powerful new tool to work with spatial data-the geographic information system (GIS). Maps, like books, are very useful devices for storing information, but they have limitations.
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