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MFworks Tutorial – 05 Cost surface

Usually, to generate a cost-of passage surface, several variables will be collapsed into one layer. These variables might be road class, average speed, traffic density, and congestion during specific time of day or other factors that contribute to the overall cost variable. The cost-of-passage surface can be defined by a variety of measurement units: time, fuel consumption, money or other possible cost units, for which the least cost passage is to be determined.

Using average speed and time as a means of inferring cost-of-passage is among the most common approach in network analysis, since it is easy to use and calculate. However, “least cost” does not always need to be “least time”; it may just as well be least fuel,

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MFworks Tutorial – 07 Dynamic Cost Surface

One option for implementing a dynamic cost surface is to use a continuously updated network, where the latest available data at the starting time of travel is used, and where the cost of travel does not change during the duration of the estimated route. Another option is to establish a network with varying travel cost per pre-defined time interval. In this case the travel cost is dependent on the starting time of travel, and the travel cost changes when the estimated route passes from one time interval to another.

In practice, the first approach involves building an application that passes on values to the cost surface used in a raster-based GIS for calculating the fastest path in a network.

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MFworks Tutorial – 09 Map Layers Needed

Map layers needed: A network, a cost surface, origin and destination point,

network.mfm

costoftravel.mfm

startstop.mfm

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The network is a replica of the Brown’s Pond study area used by Tomlin. The cost surface are fictitious values, 1-4, indicating impedance. Origin and destination were derived by assigning the values 999 and 998 respectively to points on the network map (startstop.mfm) and then extracting each point using Recode.

MFworks – step by step

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