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LINE DATA

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LINE DATA http://www.nr.usu.edu/Geography-Department/rsgis/GIS/Lectures/lec3/li...1 of 3 12/10/2004 2:17 PMLINE DATA The line is made up of an ordered set of coordinates linked in a chain to represent the shape and length of afeature such as a road. The decision to represent a feature as a line is scale dependent if the linear featureoccupies space at a 1:1 scale.Other terms for line are ARC and VECTORThe coordinates used to define the length and shape of a line are redefined points linked together. The termsthat describe the points used to define a line are NODE and VERTICE A NODE is located at each end of the line identifying the start and end. VERTICES define the shape of the line and occupy the location between the two nodes NODES- three types:TRUE NODES: a true node is located at the intersection of three or more arcs and forms the junctionbetween the arcs. PSEUDO NODES: are located between two arcs linked together. In this use, the node resides at thenormal location of a vertice and acts to separate the characteristics of two sections of the same line . DANGLING NODES: are located at the end of one arc defining it's end and not linked to another arc.LINE DATA http://www.nr.usu.edu/Geography-Department/rsgis/GIS/Lectures/lec3/li...2 of 3 12/10/2004 2:17 PM EXAMPLES OF LINE FEATURESNETWORKS Infrastructure networks Transportation networks - highways and railroads Utility networks - gas, electric, telephone, water Airline networks - hubs and routes Natural networks - River channels ATTRIBUTES Direction of traffic, volume of traffic, length of road section, number of lanes, time to travel Diameter of pipe, direction of gas flow Voltage of electrical transmission line, height of towers (nodes) Number of tracks, number of trains, gradient, width of most narrow tunnel, load bearing capacity ofweakest bridge EXAMPLE OF NODE ATTRIBUTES:LINE DATA http://www.nr.usu.edu/Geography-Department/rsgis/GIS/Lectures/lec3/li...3 of 3 12/10/2004 2:17 PMPresence of traffic lights, presence of overpass, names of intersecting streets Presence of shutoff valves, transformers Attributes of some nodes (e.g. names of intersecting streets) link one type of entity to another (nodes tolinks) NETWORKS CAN BE USED AS LINEAR ADDRESSING SYSTEMS E.G. if it is known that the block contains houses numbers from 100 to 198, house #124 wouldprobably be 1/4 of the way along that link Go back to previous page Go back to GER home pageAuthor: R. Douglas Ramsey


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