1 / 16

Multimodal Analysis

Multimodal Analysis. Using Network Analyst. Outline. Summarizing accessibility Adding transportation modes to a network Linking transportation networks. Summarizing Accessibility. General method adjust default “trimming” of service area calculations

smccormick
Download Presentation

Multimodal Analysis

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Multimodal Analysis Using Network Analyst

  2. Outline • Summarizing accessibility • Adding transportation modes to a network • Linking transportation networks

  3. Summarizing Accessibility • General method • adjust default “trimming” of service area calculations • Untrimmed gives large service area polygon • Basically, minimum convex hull • Some oddities at edges • Trimming shows areas near network • 1.6km trim might be U.S. max walking distance • Does not take into account stops • When visual isn’t enough… • Export service area polygon into separate file • Use this file for spatial selection, or overlay as appropriate

  4. Example 1: Summarizing Accessibility • Goal: find overall population within 1 hour of Albacete by current rail network • Ignoring within-city accessibility issues for now • General Method • Create a service area of 1 hour from Albacete along current rail and export as a polygon • Select city points based on exported polygon • Summarize attributes of selection city points

  5. Summarizing Service Areas, Part 1 • Set service area analysis preferences • Layer Properties->Analysis Settings • Impedance: Hours (Hours) • Default Breaks: 1 • Polygon Generation • Polygon Type: Detailed • Trim Polygons: checked • Value: 1 mile • Create a service area of 1 hour from Albacete along current rail • Click Network Analyst Toolbar -> Solve button • Export service area polygon • In main map table of contents, right mouse on Polygons layer inside Service Area Group • Select Data->Export and find it a home

  6. Summarizing Service Areas, part 2(Standard ArcGIS Point in Polygon Method) • Selecting Points in a Polygon • Add “Urban Areas” Spanish Urban Points 2005, if necessary • Main Menu Selection->Select by Location • I want to: “select features from” (default) • The following layers: “Spanish Urban Points 2005” • That: Intersect • The features in this layer: [your service area polygon name]

  7. Summarizing Attributes of Selected Points • Simplest • Open attribute table • Right mouse on Pop2005 column heading • Select “Statistics” • Look at / copy and paste out “Sum” • More flexible • Export attribute table data into new table • Re-add summary table back into map document/layout • Use 9.2 graphing functions (Attribute Table Options button->Create Graph) • Even More flexible… • Export using dbase file format, then open in Excel • Let’s you actually get a “bottom line” summary together with table

  8. Summarizing Service Areasversion 2 • Goal: to count only urban areas within walking distance of station • Presuming, for the moment, that walking distance is U.S. standard 0.25 miles (!) • Method • Use NA preferences “trim polygons” to control network buffering, or “no trim” for broad service region • Use standard map overlay functions to combine accessibility polygons with land cover, etc.

  9. Example Polygonal Overlay Based on Service Areas • Add “Urban Areas” to map • Calculate a service area polygon • Export that service area and add to map • Use “Intersect” command • Layer 1: service area polygons • Layer 2: existing urban areas • Output: urbanized polygons in service area

  10. Creating Multimodal Networks In ArcGIS Network Analyst

  11. Key Concepts • Network Analyst General Concepts • Start with line segments and nodes (normal line layer) • After “building” network dataset, have • Edges (2 per line segment, representing potential movement in each direction) • Junctions (topologically joining adjacent edges)

  12. Network Analyst Concepts 2 • NA models connectivity relationships separately from topological relationships • Topology • Deals with how things are connected • In ArcGIS, connections require a shared vertex • Connectivity • NA Only • Depends on topological connections • But can go beyond them (e.g.”no left turn” restriction)

  13. Building Network Datasets 1 • Ensure that existing topology allows connections where you want them • In particular, look for lines crossing without a shared vertex • To add vertices, two methods • Use Workstation Arc/Info command line clean/build • Use “Integrate” command

  14. Building Network Datasets 2 • Add Connecting Segments between modal networks to ensure connections • Manual Method – Use Editor • (precise but slow…) • Automatic Method • Requires ArcScript (arcscripts.esri.com) • “AutoAddLines” • Input station points, roads network • Outputs new lines from station points to closest road • Not perfect since closest isn’t always correct – see Alabcete station

  15. Assignment • Same as in-class exercise, but now using multimodal dataset

More Related