GEOG 863
GIS Mashups for Geospatial Professionals

6.1.2 Using a Custom Locator

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Esri’s World Geocode service is suitable for many apps, particularly those built at a global or continental scale. However, for apps built for relatively small areas of interest, it may be possible to utilize a locator built using data from an authoritative source, such as a city or county. The advantage to using a locator from such a source is that it is much more likely to be kept up to date (e.g., to contain new subdivisions).

Have a look at this example built using a locator maintained by the City of St. Paul, Minnesota. The first step in creating an app like this is discovering the desired locator. Many locators can be found in ArcGIS Online by searching for locator in the Tools category.  (1277 Madison St is an address in St. Paul if you're looking to try the locator.)

Once you’ve identified the ArcGIS Server REST endpoint of your desired locator, incorporating it into your app involves modifying the Search widget’s sources property. In my example, I included only the St. Paul locator, but as the property name implies, you can wire the widget up to multiple locators (e.g., you might have locators available for adjacent jurisdictions). We’ll see a multi-source example later in the lesson.

As explained in the SDK, the Search widget can have its sources property set to a LocatorSource, FeatureLayerSource, or some combination of the two. Looking at the LocatorSource documentation, you’ll notice that a LocatorSource object has some of the same properties mentioned on the previous page (e.g., popupEnabled). While perhaps a bit confusing, this duplication allows for having different settings for these properties on a source-by-source basis. For example, you might have a reason to disable popups for one of your widget’s sources, but enable them for another.

Getting back to the St. Paul example, the sources property is set using a single LocatorSource object. Unsurprisingly, the most important property to set for this object is its locator, which should be set using the REST endpoint of the locator service.

From there, because the widget provides just a single text box, you’ll want to look for matches against the locator field that is labeled as the Single Line Address Field in the REST Services Directory. In the case of the St. Paul service, that field is called SingleLine.

Finally, the placeholder property is used to provide a prompt or hint to the user on what should be entered in the search box.

In addition to its locator, there are several other LocatorSource properties that you might want to set. Here are a few of them:

  • autoNavigate – do you want to zoom to the selected location?
  • countryCode – used to restrict searches to a single country (e.g., "US")
  • resultSymbol – used to customize the symbol used to show the selected location
  • zoomScale – used to control the scale that the app will zoom to after finding a match