I have been tasked with creating a feature class or map showing 2.5 miles (driving distance) from each of our Fire Stations. I built a network, but now I do not know how to proceed! The network is local to my computer and is in geodatabase format. We are licensed for Network Analyst and ArcInfo.
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Some particulars to add beyond the information Dan Patterson provided:
- Make sure your Street Network is solid before running this. My experience is that it is not hard to build a network, but to actually build a good network that provides realistic results can take a considerable amount of time. There are a variety of issues that come up when putting together a street network that works with Network Analyst, so be sure to check the data thoroughly before hitting the "Solve" button on the Network Analyst toolbar. In particular, make sure you have connectivity between all your linework as expected. Additionally, double-check all the network-specific attributes, like for example "OneWay", as it is easy for a few attributing mistakes to totally sink an analysis.
More resources:
Network Analyst Tutorial
http://help.arcgis.com/en/arcgisdesktop/10.0/pdf/network-analyst-tutorial.pdf
Tutorial - Network analysis data prep
Network analysis - 99% data cleanup and 1% analysis
Chris Donohue, GISP
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One more bit to add. If you haven't done Network Analysis before, be aware it can take a bit of time to figure out. It's an odd duck of an extension, having originally been designed by another firm then bought and rebranded by ESRI. The result of this is the way it operates is different in several ways than other extensions. Plus the instructions in some cases are worded using terminology that is used differently in other parts of ESRI software, which can add to the confusion.
So I'd take some time to run through the tutorials and get your feet wet before doing your analysis. Also, if your organization has funds, the Network Analysis class given by ESRI Training is a good way to get going. In particular, if the requested analysis is considered life-critical, I would lobby hard for training and also the time to do a solid analysis.
Chris Donohue, GISP
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A 2.5 mile drive distance is only part of the issue; drive time aka response time is something that needs to be considered as well. An attribute to your core center line data should include a speed limit; with a little 10th grade algebra you can convert mph or kmh to time needed to traverse an given road segment in minute units. Make sure too that you have a one-way attribute; running unit up an off ramp typically draws the scorn of battalion chiefs
I'm going to offer a slightly more risk friendly approach than my respected colleague Chris D for a moment; I personally think that running various scenarios in Network Analysis is a good way to get your network into solid shape. I've been running NA for fire/ems dispatch for several years now; not saying I haven't had a hicup or three along the way, but start doing some testing, and subsequent tweeking. You'll get an idea in a hurry where the problem areas are.
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I'll second what Joe Borgione said. Mileage is nice, but response time will ultimately be more important.
As Joe mentions, plan for this to be an interative process. Do a run, check the results, research where things went awry, tweak the network. Rinse and repeat.
Field check the results. For example, don't assume the street centerline you were given is correct in its assignments of which streets are one-way.
And even once it is solid, realize other organizations will do things over time that will cause you to have to update your network on a regular basis. Some examples: new development, road alterations, implementation of "street calming" measures.
In the longer term, I would also highly recommend going over to see your Dispatch folks and see what it looks like from their perspective. Not only can they show you examples of where the system isn't working as well as expected, but you can also get unique insight from them that will allow you to then tweak the network to provide better results.
Ben - Sorry if I bombarded you with too much information - but just wanted to pass on some words of wisdom learned the hard way....
Chris Donohue, GISP
Once you have service area layer created and loaded your fire stations as facilities right click your service area group layer in your table of contents and select properties. I like to select use generate lines on the line generation tab. On the Analysis Settings tab set your impedance and default breaks close properties box and on your NA tool bar select solve.
You want a service area
Service area analysis—Help | ArcGIS for Desktop
general information on all requirements can be found in the help topic
Types of network analysis layers—Help | ArcGIS for Desktop