Modeling Path & Movement PDF

2 Modeling Path in GIS GEOG300 / NRES698 ❖ Network analysis...

2 Modeling Path in GIS GEOG300 / NRES698 ❖ Network analysis − best path alone the route system MODELING PATH & ❖ Overland path analysis MOVEMENT − least cost path cross overland P. Bai Common Network Problems What is the quickest way to What fire incidents can be reached 3 Network Analysis 4 get from point A to point B? within five minutes of fire stations? An operation in GIS which analyses the behavior of flows within and around geographic or real world networks and location ❖ The best (fastest/shortest) route across network(transportation) What market areas does the business cover? ❖ The closet facility ❖ Identify the service area ❖ Vehicle Routing ❖ Location allocation Where should we open a new branch of our business to maximize market share? How can we route our fleet of delivery vehicles to minimize overall transportation costs and improve customer service? 1 5 Network Analysis 6 Best Route Point-to-point analysis – best route The most common routing problem. It consists of a set of points to find the most optimal route based on specific criteria. ❖ Shortest Distance –accumulates all distances, as you travel out from one point to the other. Then, it finds the route with the least distance. ❖ Fastest route –takes into account speed limits, road classification, and other costs to determine the least travel time. ❖ Find Nearest – finds the nearest destination based on a starting point with multiple potential destinations. Shortest Path Fastest Path Quickest delivery path Network Analysis - Closest Facilities Network Analysis - Service Areas Elementary school 7 8 catchment (800m) ❖ Hospital Identify the service area within certain driving time/distance ❖ Fire station ❖ Hospital ❖ Fire station ❖ Gas station ❖ Schools catchment ❖ Corner store Shopping area ❖ Corner store ❖ Shopping mall 2  Shopping area within 0.5, 1, Shopping area within 500m, Shopping area within 2 minutes driving 1000m and 150m distance 1000m distance 9 10 Network Analysis Vehicle routing - Optimize Fleet ❖ find the most efficient route for delivery, repair, transit, or any type of fleet service. Vehicle routing systems help transport managers plan and optimize their daily vehicle routes, and reduce both fuel costs and fleet size 11 Network Analysis 12 Components of Network Analysis Location-allocation - Optimal Site Network dataset - A Network dataset is designed to support network analysis. Location-allocation is a form of optimization A network dataset define models designed to find the optimal location for ❖ A Line feature class - used for traverse over network service provision across region given the spatial − Transportation (street, highway…) distribution of demand for that service − Stream network ❖ Optimal site selection takes into account the ❖ Junction points - intersection among lines to model such as turns, constraints, etc. demand to locate the best location given several facilities. − The intersection of lines ❖ It helps business owners pinpoint optimal location ❖ Attributes – impedance used to measure and evaluate the best routes, locations, and for their store. It can also compare with competing area etc. stores to target market share. − Impedance – time, distance, capacity etc. 3  Modeling Movement – Least Cost Path PG network 13 dataset 14 PG Street Attributes 15 Modeling an Overland Path - Least cost path 16 Modeling an Overland Path Pipeline Routing – If you want to find the most cost-effective route for a pipeline, you’d likely want to design it Modeling an overland path in GIS is a procedure for finding an optimal route where it costs the least. For example, the cost distance layer would include weighted values from population between two points through continuous space that minimizes costs. density, environmental sites, and proximity to water. Impediments would be anything you can’t cross like cemeteries, restricted areas, or sacred sites. "Cost" in this sense can have a number of connotations, including: Hiking Trail Planning – The “cost” would be very different for planning a family-friendly hiking trail. In this case, ❖ Actual monetary expenditure in construction, you would want to build it on the least amount of slope so it’s safe to climb. As you go from the start point to its ❖ Time and effort required to travel, and destination, you want to “buy” the lowest “cost”, which would be the least amount of slope. Any route to the ❖ Negative environmental impacts. top equals the same net change in elevation. But the least cost path accumulates the least amount of slope from start to finish. ❖ Etc. Steps ❖ Specify the origin ❖ Choose the method for calculating distance ❖ Determine the cost ❖ Specify the movement factors ❖ Create the cost distance surface ❖ Create the spread surface, path, or corridor 4 17 Mapping Distance - Euclidean Distance 18 Cost-Weighted Distance The cost distance is similar to Euclidean distance, but instead of calculating the actual ❖ Straight Line Distance: Euclidean Distance distance from one location to another, the cost distance determine the shortest weighted Each cell value indicate the straight distance to the closest source distance from each cell to the nearest source location. ❖ Cost Surfaces: The minimum cost of reaching cells in a layer from one or more sources ❖ Friction Surfaces: Used to calculate the travel costs. Ex. Slope Cost Surface Cost Surface 19 20 A cost surface is a raster grid in which each cell value is the cost that a particular activity or Slope Class Value Slope Range Description object would be in that cell. It can also be an indexed value based on costliness. Costs could 1 0–3 Flat 5 3–6 Moderate be measured monetarily or in other ways such as amount of time. 1000 >6 Steep Land type Class Value Land Type 50 Barren Surfaces, Recently Burned, Recently Logged 100 Old Forest, Young Forest 500 Sub alpine Avalanche Chutes Cost Surface 1000 Alpine, Glaciers and Snow 5000 Wetlands, Fresh Water Flow Class Value Value Range accumulation 0 0 (water) 5000 for up to 5000 cell accumulation, 10000 for 5,000 to 50,000 cell accumulation, and 50000 for more than 50,000 cell accumulations). 5 21 22 Cost-Weighted Path the cost distance determine the shortest weighted distance from each cell to the nearest source location. Land Type Reclassify Landtype cost Slope class Flow accumulation class Land class Vegetation Reclassify Vegetation cost Overlay Slope Reclassify Slope cost Origin Cost Surface Destination Cost Distance Least Cost Path 23 Modeling Movement - Corridor 24 Corridor – Least Cost Corridor ❖ A corridor analysis is used to determine an "optimal corridor" between two points or zones ❖ Corridor analysis returns a raster in which the sum of the cost distances (accumulative costs) for each of the input cost rasters is calculated for each cell location 6 THE END 7