Plotting Your Own Locations on a Map
To map data points onto maps, you need both latitude and longitude coordinates in your data. You can even create custom maps in Tableau for just about anything.
It would be impractical for Tableau to monitor and save every possible location in the world. If you have specific places you want to plot on maps that Tableau doesn’t automatically recognize, you can enable this using two different methods. You can either add the specific longitude and latitude to your source data, or you can import custom geocode lists into Tableau.
Adding Custom Geocoding to Your Data source
Custom geocoding is a more flexible way to plot your data on a map. Custom geocoding is available for all workbooks on a computer once the custom geocoding data is imported. The custom geocoding data will be copied into any packaged workbook (.twbx) or published workbook that uses a custom geographic role. This will make the workbooks about 40 MB larger.
If you upgrade Tableau Desktop, you may need to refresh your custom geocoding to take advantage of any fixes made to the geocoding data in Tableau.
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In custom geocoding, you can use additional columns to define larger geographic locations. For instance, if you are creating a set of US census tracts, you may need to define which US county they fall in. You can include additional columns to define larger geographic locations in the import file.
You can also use multiple files for multiple geographic roles that have a matching relationship, meaning they share larger geographic data, such as country or state/province. Once the custom geocoding data is imported, you will see additional geographic roles that can be assigned to your geographic data.
You must obtain geographic coordinates in the form of longitude and latitude values that you provide to your data set in order to add custom geocoding to your data source. There are many free web-based geocoding services that provide this information. My personal favorite is www.gpsvisualizer.com. Figure 5.9 shows a list of jazz clubs in the metro New York area that have the necessary latitude/ longitude data added.
Figure 5.9: Custom location list
The sample data partially in view in figure 5.9 includes over five hundred addresses. You can see the coordinates in the right columns. Using the custom latitude and longitude, data allows you to plot each location on its specific address. Figure 5.10 shows the custom plot within a tooltip exposed displaying additional location details.
Figure 5.10: Dark style map with address detail
The column and row shelves hold the custom latitude and longitude coordinates that place the marks on the map. The Tooltips were customized to show the street address, phone number and venue information. The dark map style was modified slightly by employing a twenty-five percent washout via the map/ map options menu.
Finally, custom geocoding lets you add additional places to an existing geographic role, such as adding new cities to the city role. It also allows you to define a hierarchy of geographic roles that extends the built-in hierarchies (e.g. census tracts in counties) or defines a new hierarchy (e.g. sub-territories in the territories).
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