> Script Details
Service area spiders
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Sep 14 2000
Status of work
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If you like Thiessen polygons and Spatial Analyst proximity assignments you'll love this script. Use this script to generate a Spider diagram shapefile with spider legs connecting service center points to only customer points closest to each service center. Use the resulting shapefile in combination with Thiessen polygons for a really cool service area analysis. An attribute item from both the service center point theme and the customer point theme as well as the distance between points is passed to the new polyline shapefile for subsequent linking.
This scripts uses Greg Ammon's code to generate Thiessen polygons. You can get his Thiessen polygon extension here. This script is a significant enhancement over existing spider diagram scripts from ESRI.
(1) Different projections will yield different results. The user is responsible for understanding why.
(2) Performing analyses on large numbers of points can take quite a while. For example, using the cities shapefile from ESRI, finding the cities closest to each state capital (50 points) from 3149 points requires that 157450 potential lines need to be examined to create 3149 lines for 50 spiders. This takes about 40 minutes on a 450MHz Pentium with 256MB of RAM. Not bad really.