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Network Analyst Service Areas not great with islands/lakes/inlets

Question asked by karen_firstname on Mar 26, 2020
Latest reply on Mar 26, 2020 by MMorang-esristaff

Hi everyone, 


I've been really struggling to understand the outputs of the Network Analyst Service Areas. I am trying to create 20km service areas around the country for my 60 facilities. There are 2 main issues that I'm coming across: 


1. We are in New Zealand and there are many bodies of water that should be excluded/taken into account when creating a service area for 'driving distance' (since you obviously can't drive to an Island). I have created polygon barriers for the bodies of water, but it will still include parts of islands/peninsulas that cannot be driven to. I'm creating generalized precision service areas because the standard precision output excludes a lot of area that I would like to be included. How can I change the polygon barriers to have a greater effect on the output? Or should I use a line barrier of the coast line to get a better result?


2. I like the output for about half of my service areas - these are the ones that aren't near any other facilities, so their boundaries don't overlap with another facility. However, the facilities that are close together have terrible split boundaries and I need to manually edit all of them to get my desired result.


My goal is to have a process that we can easily run whenever a new facility opens or one closes, but so far I haven't been able to find an easy solution. The network analyst service areas provide a good starting point but need a lot of work to get to a point where I could present it and use it for analysis on other projects. Any ideas on how I can update the parameters or use a different tool to achieve better results? 


Here is a screenshot of an example (Auckland) where the service area includes the end of a peninsula, but should not.