Arizona State University Using GIS to Generate Mutually Exclusive Service Areas Linking Travel On and Off a Network Christopher Upchurch Michael Kuby Michaek Zoldak Anthony Barranda Arizona State University
Light Rail Research Station Area Factors Service Area Requirements Walking Distance Mutually Exclusive Network Based
Available Buffering Techniques Euclidian Buffers Circular
Circular Buffers
Available Buffering Techniques Euclidian Buffers Circular Thiessen Polygon
Thiessen Polygon Buffers
Available Buffering Techniques Euclidian Buffers Circular Thiessen Polygon Combined Circular and Thiessen Polygon
Combined Circular and Thiessen Polygon Buffers
Available Buffering Techniques Euclidian Buffers Circular Thiessen Polygon Combined Circular and Thiessen Polygon Network Based Buffers ArcView Network Analyst
ArcView Network Analyst Service Areas
ArcView Network Analyst Service Areas
ArcView Network Analyst Service Areas
Available Buffering Techniques Euclidian Buffers Circular Thiessen Polygon Combined Circular and Thiessen Polygon Network Based Buffers ArcView Network Analyst ArcView Network Analyst + Thiessen Polygon
Service Area Requirements Walking Distance Mutually Exclusive Network Based
LOON Method Linked On-Off Network Method Raster Based Hierarchical Approach Distance Off the Network Distance On the Network
Step 1: Initialization Network Impedance Grid Source Grid Off-Network Impedance Grid
Network Impedance Grid
Source Grid
Off-Network Impedance Grid
Step 2: Calculate Lowest Network Distance Cost Distance Command Finds: Closest Source Node for Each Cell Distance to that Source Node Using: Source Grid Network Impedance Grid Output: Raw Distance Grid Allocation to Source Node Grid
Raw Distance Grid
Allocation to Source Node Grid
Step 3: Create a New Set of Source Cells Hierarchical Approach Distance On the Network Distance Off the Network New Source Cells for Second Cost Distance Command
Raw Distance Grid
All-Network Source Grid
Step 4: Calculate Off-Network Distance Cost Distance Command Using: All-Network Source Grid Off-Network Impedance Grid Output: Off-Network Distance Grid On-Network Distance Grid
Off-Network Distance Grid
On-Network Distance Grid
Step 5: Calculate Total Distance Off-Network Distance + On-Network Distance
Total Distance Grid
Step 6: Trim and Reclassify the Total Distance Grid Reclassify all cells less than maximum distance as 1 Reclassify all cells more than maximum distance as “no data”
Buffer Mask Grid
Step 7: Create Final Buffers Buffer Grid = Allocation to Source Node Grid x Buffer Mask Grid
Buffer Grid
Proof of Concept What Benefits does the LOON method have over other techniques for generating service areas?
LOON Service Areas
LOON vs. Circular + Thiessen
LOON vs. ArcView + Thiessen
Statistical Comparisons ArcView vs. LOON Employment of Sacramento buffers calculated using both methods Citywide average area and employment fairly close, within 5% Average percentage difference greater than 85%
Questions? Step by Step Instructions are available at: http://geography.asu.edu/mkuby/gis_buffer_steps.html Questions?