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ArcMap Desktop: Addreses & coordinate data (geocode; XY data)

Geocode Addresses

ArcGIS can determine the location of addresses, for instance if you have a spreadsheet with address data.  You need to have a steet layer formatted appropriately. ArcGIS will create a point at the location of each address.  Clean data is essential. Quick Tour of Geocoding.  Tutorial from ESRIOnline help from UNC-Chapel Hill.  Online help from Harvard.  Online help from Tufts.

There are some ready-to-go locator files included in the Esri Data & Maps product, under Streetmap North America. These can be downloaded to the computer that you're using. We also have 2013 adn 2014 address locators on the S: drive (scratch drive) available from the 12 computers in the Data and Visualization Services computer lab.

You can make your own address locator from some layers of streets or similar GIS layers.

You will also be able to connect to the ArcGIS Online Geocoding service. Contact askdata@duke.edu to get an ArcGIS Online account and to ask about geocoding procedures:

  • there are limits on the number of address that the Duke account can geocode, and
  • the online geocode engine often produces a large number of false positives, so the effort of using a locally installed locator file will probably provide more accuracy.

Plotting X/Y Coordinates

You can plot your data that has coordinate information (latitude/longitude or any other coordinate system) into ArcGIS.  The program plots the locations as points on your map. Online help.

VERY IMPORTANT:  In the Add XY dialog box, look at the coordinate system that ArcGIS is assuming your data is in before you click through to create your points. The default will be whatever your data frame is in. For instance, if your data frame uses NAD83 State Plane North Carolina Feet, then ArcGIS assumes your tabular coordinates are in feet, not degrees. If these are really Longitude (X) and Latitude (Y) coordinates in degrees, you must change your coordinate system to unprojected (geographic) coordinates, typically WGS84 (the last choice under Geographic...World).

The plotted points are just pointing back to your tabular data; they don't represent a new layer. If you then need to use tools on the point layer, such as a Spatial Join (see other box), then you will first need to export it as a feature class (e.g., shapefile). Online help.

Associating with Features in Other Layers (Spatial Join)

Users frequently want to determine the geographic areas that each point in their point data falls within (e.g., which Census tract or block group each is in, which police precinct each is in, which school attendence zone each is in).  This allows associating, with each point, data that is aggregated by such polygon features (the geographic identifier, such as the name of the Census tract, for example, and any other variables in that layer's attribute data).

This can be done using a Join procedure based on location (Spatial Join), which associates all the attributes of a join feature (e.g., a polygon) to each of the target features (e.g., each point) that is within it.

Subject Guide

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Mark Thomas
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