Module 12 - Geocoding and Network Analyst

This week, we learned how to create an address locator, conduct geocoding by address matching and matching unmatched addresses, to create a route analysis layer with Network Analyst, and how to compute optimal routes for our stops. The larger picture, the product we are creating, is a map of EMS locations within Lake County, and a sample route from one of them.

First, I downloaded TIGER/Line shapefiles for the area in question from the U.S. Census Bureau website and imported them into our geodatabase. Using ArcCatalog, I found my geodatabase and created a new address locator. In ArcMap, I added the roads and EMS features and selected Geocode Addresses on the EMS data table. The geocoder automatically matched our addresses, and a good guideline is to have an unmatched address rate of 5% or less. My unmatched rate after the geocoder finished was 32%, so I needed to manually rematch the unmatched addresses. Under the rematch window, I selected Unmatched Addresses and saw the list of candidates under each one I selected. I zoomed into the first candidate suggestion just to see a closer look at the area. Then I went to Google Maps and found my unmatched address there. I visually found that location on my map and used the Pick Address from Map tool to select that spot to manually rematch the unmatched addresses. There was one I was unable to find, which left the unmatched rate at ~5%.

Next was selecting a route using Network Analyst. Network Analyst calculates the nearest network location and symbolizes the stop with the "Located" symbol. Using the toolbar, I selected the address locator that I had created. I found the EMS site at 11 Yorkshire Drive in Paisley as that is the EMS site I want to create a route from. Using network analysis to select a route here is just a matter of clicking on the map where I want a stop to be. I selected 3 stops for my route. I had some trouble with my initial route, as the stops kept showing up as "unknown address", even though the rest of the route and directions were working correctly (it used the edges in the roads file for directions). I don't know what caused the issue, but when I selected 3 new stops (a totally different route) it worked fine. I set up the parameters for analysis in the Network Analysis toolbar and computed the best route in distance and time.

Then I created the map. To do this properly, I needed to grab the county boundary file from a previous lab. I projected the data to the projection currently being used in this lab and made a new layer with just the Lake County boundary (using Select by Attributes). I added a second data frame to show my optimal route from EMS Station 11 in closer detail. In the first data frame I added an extent frame to show where in the county EMS Station 11 and my route was located. I arranged the map and added the essential map elements, and the final map is shown below.

This week's lab wasn't quite finished yet. We learned about ModelBuilder, which is an application that allows you to create, edit, and manage models. Models in this context are defined as workflows that string together sequences of geoprocessing tools, feeding the output of one tool into another tool as input. This was an online ESRI training module that taught us the basics of using this application. I like this tool as it helps me to visualize what I'm trying to do, both the individual steps and the larger picture of the final product, especially if there are a lot of intermediate steps. It makes it easier when you're buffering different layers to different geographic extents; I feel it helps me to keep track of what input is affecting what output. I find that using a model will likely help me "solve" a problem in that it's easier to see what kind of data I need to collect to produce a desired output. Learning about ModelBuilder was my favorite part of this module.