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URBDP 422 Urban and Regional Geo-Spatial Analysis

URBDP 422 Urban and Regional Geo-Spatial Analysis. Network Analysis Team Work Time VIII February 25, 2014. Overview. What is Network Analyst Types of Analysis Types of Networks Network Analyst Tools Network Components Designing and Creating a Network Dataset Example Tips and Tricks.

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URBDP 422 Urban and Regional Geo-Spatial Analysis

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  1. URBDP 422 Urban and Regional Geo-Spatial Analysis Network Analysis Team Work Time VIII February 25, 2014

  2. Overview What is Network Analyst Types of Analysis Types of Networks Network Analyst Tools Network Components Designing and Creating a Network Dataset Example Tips and Tricks

  3. Example: estimate the draw a park may have with local residents – that commute via car verses bike

  4. What is a network? System of interconnected elements, such as edges (lines) and connecting junctions (points), that represent possible routes from one location to another.

  5. What is Network Analyst? The ArcGIS Network Analyst extension allows you to build a network dataset and perform analysis on a network dataset Used primarily on Transportation Networks

  6. Terms • Facilities and incidents: the start and end points of routes • Fire stations and house fires • Barriers:represent those parts of the network that are specified as impassable • Underpasses or tunnels that are too short or narrow for large fire engines • Routes:the least cost path between two points in the network

  7. Types of Analysis • Answers 8 main problems, questions, or tasks: • Drive-Time Analysis • Point-to-Point Routing • Route Directions • Service Area Definition • Shortest Path • Optimum Route • Closest Facility • Origin-Destination (OD) Cost Matrix

  8. Class questions Brainstorm: • Think of 2-3 questions related to planning that would be best addressed with a network analysis software? • How might network calculations help you answer questions related to your class research project?

  9. Network Example: Optimal Routing • Delivery schedule and route • Best route to single or multiple destinations • Bus routes • Multi-tasked day • Running errands

  10. Optimal Route: Shortest Route

  11. Sewer Pipes Exploded on streets and Have formed a barrier for delivery!

  12. The food still gets there!!!!

  13. Types of Networks • Transportation Network • Undirected networks. • Free to decide the direction, speed, and destination of traversal. • For example, a person in a car traveling on a street can choose which street to turn onto, when to stop, and which direction to drive. • Restrictions imposed on a network are guidelines • Modeled using network datasets.

  14. Types of Networks • Utility Network • A utility network is directed. • Flows along the network based upon certain rules built into the network. • The path is predetermined • The engineer controlling the network can change the rules of the network by opening some valves and closing others to change the direction of the network. • In ArcGIS, utility networks are modeled using geometric networks.

  15. Network Datasets Networks used by ArcGIS Network Analyst are stored as network datasets A network dataset is created from the feature source or sources that participate in the network It incorporates an advanced connectivity model that can represent complex scenarios, such as multimodal transportation networks It also possesses a rich network attribute model that helps model impedances, restrictions, and hierarchy for the network The network dataset is built from simple features (lines and points) and turns

  16. Network Analyst Software • This extension is composed of a number of parts: • wizard to create a network dataset (in ArcCatalog) • Network Analyst toolbar (in ArcMap) • dockable Network Analyst window (in ArcMap) • geoprocessing tools contained within ArcToolbox

  17. Creating a Network Dataset • Prepare the Feature Dataset and Sources • All Participating feature classes MUST be in the same Feature Dataset • Prepare the Sources for Appropriate Roles • Direction, Miles, or Time • Prepare Turn Feature Classes • Create Network Dataset Using the Wizard • Build the Network

  18. Creating network data using wizard

  19. Network Elements • Three types of network sources that participate in the creation of a network dataset: • Edge feature sources • Junction feature sources • Turn feature sources.

  20. Network Elements • Each feature class that participates in a network as a source generates elements based on its assigned role. • Line feature classes are used as a source for edge elements • Point feature classes are used to generate junction elements. • Turn elements are created from a turn feature class.

  21. Designing a Network Dataset Select the Source Workspace Identify the Sources and the Role they will Play Model Connectivity Define Attributes and Determine their Values

  22. Specifying network setup in wizard • Model turns • Connectivity • Elevation data • Cost – criteria for evaluating optimal route (e.g. often distance)

  23. Network Attributes • Cost • Measure and Model Impedances • Descriptors • Describe Characteristics • Restrictions • One Way Streets, No Pedestrians • Hierarchy • Order Assigned to Network Elements

  24. Network Evaluators • Field • Value from a Field (e.g. meters) • Field Expression • Calculate Minutes - ([Miles] / [SPEED]) * 60 • Constant • A Set Value • VBScript – model complex attributes

  25. A network dataset has been created • Now you can load your dataset into a Map Project.

  26. Network Analyst Software • This extension is composed of a number of parts: • wizard to create a network dataset (in ArcCatalog) • Network Analyst toolbar (in ArcMap) • dockable Network Analyst window (in ArcMap) • geoprocessing tools contained within ArcToolbox

  27. Network Analyst Toolbar Create Network Location Tool Solve Network Analyst Window Directions Window Network Identify Build entire network dataset Select/Move Network Location Tool

  28. Calculation options • Closest facility (gasworks park example) • Create optimal route (food delivery example)

  29. Example: gasworks user area • specify start and end points • “facilities” are the start (circles) • “incidents” are the end points of routes (squares)

  30. facilities, the start (circles) Incidents, the end points (squares) e.g. gasworks park and home addresses

  31. Resulting routes between facilities and incidents

  32. View directions

  33. Summary Stats

  34. Network Analyst Toolboxes • Used for batch Geoprocessing • Model Builder • Scripting • Python • Jscript • VbScript

  35. Tips and Tricks Build network datasets Feature class to feature class conversion Common Problems in Feature Class Multiple street names

  36. First and Foremost • Form your Network Dataset: • Available from Commercial Vendors • Dataset comes with routing attributes so spatial analysis can be performed. • Construct Privately • Takes time, skilled labor, and information regarding geographic region • Can buy or personally construct geographic region data

  37. Network Dataset • The logistics of a Network Dataset and how to manipulate it: • Usually one feature class with all geometrical data regarding streets • Polyline geometry -> vector data model • Format: Must be shapefile or a geodatabase feature class. • IfNot, then format using the Feature Class to Feature Class tool in ArcToolbox

  38. Common Problems in Feature Class • Multiple street names for one polyline • 1 road labeled Hwy 4, University Way, and Main St • Duplicate street names and Misspelling • 2 independent polylines with same name • Lack of endpoint connectivity • Connected roads do not connect • Lack of desired Field data/attributes • Information regarding polyline attributes is not listed, such as paved or unpaved, toll road or not. Must join the remote attribute table to the field desired in working attribute table

  39. Multiple Street Names Here one street ID is represented by four Names. The Network Dataset interprets this As if there are four streets at this one location. Assign a primary name to the street ID and then list the other names As secondary, tertiary, etc. This is done by placing the non-primary names In Fields labeled, Name1, Name2, Name3, etc.

  40. Multiple Street Names • Due to lack of creativity, some locations may have duplicate names. • Beware: Upon running a Network Analyst tool such as Driving Directions, Optimal Route, etc. the tool may choose the wrong street with the same name. Use match to choose the correct one. • Misspelling is a common error for street attributes, must edit personally. • If the shapefile or geodatabase does not have endpoint connectivity then continuous roads may appear as dead ends. This will obstruct accurate spatial analysis of street class. • Can use the integrate tool in ArcToolbox to fix endpoint problems. • Also can use ArcEditor and run a Snapping program with a given tolerance to eliminate such problems.

  41. Take-home messages Network Analysis allows you to perform a range of analytical functions such as optimal path analysis, route direction, and service area definition Difference between transportation (undirected) and utility (directed) networks Networks have a variety of elements, attributes and evaluators Designing and creating a Network Dataset requires defining sources, create connectivity, and assign attributes

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