3-Layer Maps is a neighborhood search tool allowing you to find places that match one or up to three (3) criteria of data on a map. The 3-Layer Maps tools can be used to download a list of addresses which fall within one or multiple criteria (using Download Points) or a list of places that met the criteria set (using Download Places). 3-Layer Maps is available to subscribers or trial users only.
To start, select 3-Layer Maps from the upper left of the screen. A “wizard” will appear on top of the map with step-by-step instructions for creating an analytic map. You can follow these instructions to create an analytic or turn off the wizard.
The page will look similar to the Maps page, with the search bar across the top and data categories above the map. To the left, however, you will see three legends; one for each data layer that you can add to the map. Unlike the Map feature, 3-Layer Maps allow you to overlay up to three thematic data layers on the map at the same time. Adjusting the ranges for each data layer as it is added will allow you to find only those places which meet all of the parameters.
To begin, enter a location in the seach bar (this works exactly as it does in the rest of the application). Click GO.
Next, add a thematic data layer from a data category on top of the map. A legend will display to the left of the map (see example). In the legend for this data layer, users may; change the year, the variables, move the sliders to set the ranges, or manually enter the values for the ranges.
- When you load the first data layer, the map will be completely purple. This is because the map is showing the entire range for the data layer loaded. You can set a specific range by moving the triangles in the slide bar or manually enter value in the fields. The map will then shade those places in purple which meet the parameter.
- Just like the legend on the maps page, users can change the year and variables used in the analytic.
- Some data layers on PolicyMap do not have ranges to select from but checkboxes. Unchecking a box will remove that indicator on the map.
- In some cases, the map will instruct you to zoom in further. This is because the analytic map defaults to the smallest geography available (usually census tracts). As a result, to view the results on the map, you must zoomed further into an area. The triangular symbol of the zoom bar on the map will indicator how far you must zoom in to be able to see data.
- – If you are creating an 3-Layer Maps at a national or regional level, then change the Shade By to a larger geography so the data will display on the map. You will need to do this to every data layer added.
- Click once on any purple area to see its value, which met the parameters set. Click onto any geography not in purple to also see its value and why it did not meet your parameter.
To add a second layer; select another data layer from the Add Data Layer menu and follow the above steps. An additional legend will display on the left of the map, users can then change the year, variable, the geography shaded by, or set the parameters for the newly added data layer. As you set new parameters for the second data layer, only the areas shaded purple on the map from the previous data layer will display places on the map which meet both conditions will shade a dark purple, and clicking onto each place will display the values for both criteria set.
Note, the map will always show the SMALLEST geography identified in the legend. For example, if you have three (3) criteria selected for Census Tracts, School Districts, and Zip Codes, the map will display Census Tracts as that is the smallest geography.
Finally, add a third layer in the same way and click on any shaded purple area to see the values for the three data layers on the map. Click on any shaded area to see the values or any non-shaded area to see why it did not meet the three parameters.
After you have setup the criteria for a 3-Layer Map, there are a few options to save, share, and even download the data.
- Save will save your 3-Layer Maps criteria to your My PolicyMap page, while Print will also save a copy to My PolicyMap but also give users the ability to create a map to share. Like all print options on PolicyMap, users have the option to give a title, choose the format, and also the orientation.
- Download Places allows a user to generate a list of all geographies and the values for those places, which met the criteria of the 3-Layer Maps. Learn more about Download Places here.
- Download Points works in conjunction Data Points. After creating the criteria of a 3-Layer Map, users can add an address/point dataset from the Data Points section in a data menu and use the Download Points function to generate a list of addresses which only fall on a geography in purple on the map. Learn more about Download Points/Sites here.
To read a full guide on all features on PolicyMap, please look at our Primer available here