Multiple Map Layers in Tableau
Tableau 2020.4 introduced multiple map layers feature to the world of data visualization with Tableau. Multiple map layers simply put – is a feature that allows you to overlay multiple geographical information in your maps.
Note that the option of creating multiple map layers becomes visible when you add a geographical field to the view. For example, in this case - the marks layer option used to create multiple map layers became visible after I created the initial filled map showing Profit by State.
Once you build the initial map in the view (forming the base layer), you can drag other geographical fields to the marks layer on the marks card - to overlay an independent layer on top of the base layer (repeat the same to add more layers to the view).
The marks layer becomes visible when you drag a geographical field to the view.
(With the multiple map layer feature, you can forget the old way of creating multiple map layers – which involved duplicating geographical coordinates to create a dual axis, then using one of the duplicates to create the second map layer, a technique that limited one to only two layers - and no more than that).
Things you can do with the multiple map layer feature
Create unlimited number of customized map layers
With the multiple map layer feature, you can now create unlimited number of customized map layers – unlike before when you could just create two map layers. And with the options of renaming each map layer – you can easily rename the multiple map layers - making navigation between the map layers seamlessly for your users.
To rename a map layer, open the dropdown menu next to the layer’s title and choose Rename… alternatively you can double-click on the layer’s title to rename it.
Create map layers using multiple data sources
The multiple map layer feature also made it possible to create map layers using multiple data sources – without the need to combine the data sources (either using relationships or joins) prior to creating the map layers.
For example, the image below shows the distribution of schools and health facilities in the slum of Kibera. Both the two data sets are unrelated and exist separately in the Tableau data sources – but by the power of the multiple map layer feature, I was able to create the two map layers (with the red shapes representing the health facilities, and the black shapes representing the schools).
Format each map layer independently
Each map layer you create contains the marks card - which you can use to encode each layer’s data by size, shape, and color – providing the flexibility needed in customizing the appearance your maps.
Toggle visibility of map layers (control layer visibility)
With multiple map layer feature, you can toggle the visibility of some of the layers allowing you to visualize only the relevant layers for the questions at hand. To toggle the visibility of a map layer, open the dropdown menu under the layer’s title, and choose Hide – alternatively, click on the control layer visibility icon next to the layer’s title to toggle the visibility of the map layer.
Disable selection on some of the layers
Ability to disable the selection on some of the layer’s – allows you to customize the end-user experience, allowing you to make some of the layers interactive, while making others remain as simply background (do not show tooltips and other interactive elements when you hover).
To disable the selection on some of the layers, simply open the dropdown menu on the layer’s title and select Disable Selection – doing so removes all the interactive elements in the layer, enabling you to present some of the layers as simply background.
Re-order map layers
Ability to re-order map layers provides the control needed to ensure that background layers that obscure other map features are drawn to the bottom. To re-order your map layers simply open the dropdown menu under the layer’s title and choose Move Up or Move Down depending on the direction you want to move the layer. Alternatively, you can grab on the layer’s title and drag it upward or downward to re-order them accordingly.
Some of the use cases of map layers
A business might want to visualize its stores, competition locations, and win/loss metrics by store to understand competitive pressures.
An NGO may want to visualize its offices, and those of partner organizations – enabling its field officers easily identify nearby offices together with their contact details.
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