Dual-axis maps in Tableau - Step-by-Step Guide

Introduction

Dual-axis maps let you combine two map layers in one view. This helps you compare different data points on the same map, like showing sales locations and customer density together.

When you want to show store locations and sales territories on the same map.

When you need to compare two different geographic data sets, like population and income levels.

When you want to overlay points and filled areas to see relationships clearly.

When you want to highlight routes on a map while showing regional boundaries.

When you want to combine a heat map with individual data points for better insight.

Steps

Step 1: Drag the first geographic field (e.g., State) to the Rows shelf

- Tableau worksheet

A map showing the first geographic layer appears

💡 Use a geographic dimension like State or City for the first layer

Step 2: Drag the second geographic field (e.g., City) to the Rows shelf next to the first field

- Tableau worksheet

Two separate maps appear side by side

💡 Make sure the second field is also geographic to create a map

Step 3: Right-click the second geographic field on the Rows shelf and select 'Dual Axis'

- Rows shelf in Tableau worksheet

The two maps overlay on the same axis, creating a combined map

💡 Dual axis merges the two maps into one view

Step 4: Click the drop-down arrow on the second Marks card and choose the desired mark type (e.g., Circle, Shape)

- Marks card for the second geographic field

The second map layer changes to the selected mark type

💡 Use different mark types to distinguish layers visually

Step 5: Synchronize the axes by right-clicking one axis and selecting 'Synchronize Axis'

- Axis on the Rows shelf

Both map layers align perfectly on the same scale

💡 Synchronizing axes ensures accurate overlay

Step 6: Adjust colors and sizes on each Marks card to differentiate layers

- Marks cards for each geographic field

The map layers become visually distinct and clear

💡 Use contrasting colors for better clarity

Before vs After

Before

Two separate maps show State boundaries and City points side by side

After

One combined map shows State boundaries with City points overlaid clearly

Settings Reference

Dual Axis

📍 Right-click on second geographic field on Rows or Columns shelf

Combine two map layers on the same axis for overlay

Default: Single axis

Synchronize Axis

📍 Right-click on axis in the view

Align scales of both map layers for accurate comparison

Default: Unsynchronized

Mark Type

📍 Marks card for each geographic field

Change how data points appear on each map layer

Default: Automatic based on data

Common Mistakes

Not synchronizing axes after creating dual-axis map

The two map layers do not align properly, causing confusion

Always right-click an axis and select 'Synchronize Axis' to align layers

Using non-geographic fields for dual-axis maps

Tableau cannot create map layers without geographic data

Ensure both fields used for dual-axis maps are geographic dimensions

Using the same mark type and color for both layers

Layers blend together and are hard to distinguish

Use different mark types or colors on each Marks card for clarity

Summary

Dual-axis maps let you overlay two geographic layers in one view for better comparison.

You must synchronize axes to align map layers correctly.

Use different mark types and colors to make each layer clear and distinct.