Have you ever wanted to control the zoom on Tableau maps without pinning the location?
Take the map below as an example, there are only 2 points, Canada and the U.S., Tableau is adjusting the zoom of the entire map to show just those marks using as much of the sheet space as possible. This unfortunately makes it difficult to recognize what countries were looking at, we just see 2 dots on some continent.
Now take the same map, but using filled shapes on a second axis to show the country outline, see how it's much easier to recognize each country?
Give it a try
Try out the filter on the dashboard below and see how each for each region around the world the filled map helps outline the countries but also adds a nice design feel.
Another use for the dual axis map and filled shapes is to replace the default map background and labels. To start make the default Tableau map completely opaque and then use the filled shapes as the map background, you can even add country or state labels for a custom touch.
Dual axis measures can be used on almost any chart type in Tableau, here is a quick walkthrough how to add them to your next viz.
Start with your regular map
Then duplicate the Latitude measure onto the rows shelf by holding CTRL. You'll now have 2 maps, one of top of the other
The next step is to overlay them on each other. Right click on the second "Latitude" measure and select "Dual Axis", you're now back to a single map but you have 2 marks card tabs, one for each axis.
As an aside, if you're doing a dual axis line chart, you will typically want the overlaid axes to have the same range and scale, to do that just right click on the second axis and choose "Synchronize Axis".
You can now modify each mark type independently, and even change the values you are visualizing, for example you could display population for one mark and birth rate on the second mark.
In this example we'll change the first mark tab to a filled map, and change the color coding to "Region".
We can add borders and transparency. Then we can switch to the circle marks, add a border, increase transparency, and up their size.
That's all it takes to do a dual axis map, and the same principles apply to line charts and scatter plots as well.
Happy dual axis experimenting and please let me know if you run into an questions and want to share your latest viz.