GIS/GPS Chapter 12

Networks

direction of flow makes something undirected/directed

Undirected

roads with having multiple choices to go

Directed

power lines have one way to go

Geocoding

process of finding a geographic location from an address

Address matching

plot street addresses as points on a map and imagine you put an address into a GPS device that has to 1st determine where the desired street address is located and using geocoded information

Geocoded fundamental components

input dataset, output dataset, processing algorithm, reference dataset

Input dataset

contains the records that the user wishes to have geocoded (usually addresses)

Output dataset

geographically referenced code generated from input (accuracy is dependent on input data and processing algorithm)

Processing algorithm

determines the appropriate positions of the input data in the output dataset based on values of each record’s attributed and the values of the attributes in the reference dataset

Reference dataset

contains geographically coded information that can be used to find the correct locations of the data in the input dataset using the processing algorithm, essentially geocoding database with similar to topologically correct transportation network geodatabase

Preprocessing

15 N Oakley Boulevard, Chicago, IL 60612, take things that are common and group them together, parsing process separates the individual components above and enables the address to be found in the reference database, common versions of the same thing are given the same notation

Address Matching

15 N Oakley Boulevard, Chicago, IL 60612, from and to addresses on the right side of road range from 1 to 31, algorithm now knows odd numbers on right and even on left, 15 would be approximately in the middle

Geocoding quality

common contributors to low address-matching rates with misspelled street names, incorrect city name, incorrect directional identifier, out of range street number with incorrect street type, using an abbreviation that’s not recognized, missing data, ket is to determine the minimum “match rate” that’s acceptable for a given project and then exceed that rate if possible

Transpiration/undirected networks

used to determine the fastest/shortest route to a location

Geometric utility/directed networks

natural systems sometimes flow in only one direction within a network ( unless manipulated by people) these are geometric utility/directed networks

Natural forces of geometric utility/directed networks

gravity and pressure act on these fluid, electromagnetic and gaseous materials can manipulate the rate of flow of material within networks by adjusting external forces

Transportation/undirected network analysis

building a topologically correct transportation/undirected network geodatabase collect source network information, build topologically correct network dataset elements, specify the network analysis to be performed and solve the problem, attribute info about a road segment/edge, network cost (impedance) information (speed limits, time required to pass through an intersection) and estimated in terms of distance, time spent, and/or other calculated variables

Attribute info about road segments

x/y coordinate of the edge segment (road), length of the road segment, 2 way traffic is permitted along the edge, only 1 way traffic in a certain direction is permitted

Optimum route

looking for a route, routes, several important parameters should be considered when determining the optimum route with the source of network, edge and turn impedance, computing the minimum network cost using an impedance matrix

Routes

minimum of 2 points and starting and ending (termination)

Minimum network cost using an impedance matrix

identify shortest distance from node 1 to 2, 3, 4, and 5, 1 to 2 is easy and so is 1 to 3, but 4 to 5 it’s trickier with needing an interactive process

Location-allocation modeling for facility location

can be organized according to the following criteria with maximize attendance, minimize impedance, maximize market share, maximize coverage, target market share

Attribute information about a stream segment/edge

x/y and perhaps z-coordinates of the source junction point (spring in the side of a mountain), x/y and perhaps z-coordinates of the end of the stream segment (where the stream intersects another stream segment), length of the stream segment, width of the stream segment/diameter of the water pipe, slope of the stream segment assuming digital elevation information is present to compute the slope

Attribute information about the intersection of 2 stream segments

valve condition (open/closed/intermediate), restriction (damn/damaged water main valve/damaged power pole)