The Incredible Power of Maps

For anyone that knows me personally or has taken my courses in the LinkedIn Learning library, it's no secret that I'm a huge fan of maps. My home office is even full of wall maps and three-dimensional globes. The intersection of geopolitical and physical boundaries over the course of history never ceases to amaze me.

Mapping Technicalities

So why maps? Maps can be a great way to visualize data in a space that's both familiar and unfamiliar to the consumers of data models. It places the key points or trends on a map so we can easily identify them. However, I've also seen a number of examples where maps weren't the best way to communicate these outcomes. When I use maps, there are a few questions I ask myself as I build them:

• Is the physical location on a map an important part of the discussion?
• What does the map share with the end user that they don't already know?
• Are there trends that become apparent on a map that would otherwise be difficult to see?

Mapping visuals are immensely helpful for communicating geographic data insights, but like any other visual, there's no one right way to use them. We'll often want to use maps in tandem with other visuals or with tooltips within a tool to make them easier to understand for the end user.

Projection Types

While the world is a three-dimensional object, the maps we use in data visualizations almost always appear on a two-dimensional plane, which means that we need to find a way to project the mapping coordinates onto a flat space. To do this, we can choose from several different types of mapping projections, like the ones we see below for world maps. The Albers and Equirectangular projection types are the two I've used the most. If the Albers projection looks a bit odd on a world map, that's because we typically see it used on a smaller piece of the map projection, like just the United States for example.

Cartesian Coordinates

Maps themselves use cartesian coordinate systems, which use latitude and longitude dimension coordinates to let us place data as single points on a map. Points on a map can be helpful for analysis like determining the locations and the amount of electricity generated from a particular source, like the hydroelectric dams in Washington, which generate roughly two-thirds of the power in the state as we can see from the dashboard in Power BI below. This particular map is done using the Azure map visual (which is currently in preview mode within Power BI).

We can also use points on a map to join them up to illustrate the impact of the flow between geographical points, like the total gas flow between individual countries in Europe. To create a flow map like this, each record representing an individual flow segment between two countries must contain a starting point and an ending point. The weight of the width is an optional third parameter. Check out how to create this particular flow map visual in the Data Dashboards in Power BI course!

Shape Maps

Cartesian coordinates let us place individual data points on a map, but it also enables us to create outline maps using a series of coordinates to create geographical shapes. These shapes can be geographical outlines that we're already familiar with, like countries, states, or counties. They can also represent shapes that we're not as familiar with, like the Nielson Media Markets map we see below for example.

Other examples of filled maps include ones that draw our eye to the important things for the end user to notice. Here's an example of the concentration of radon by US county. While I know that the map is grainy (check it out on the Lawrence Berkeley National Lab website) and the juxtaposition of green and red in the color scale next to each other make it difficult to read. It does, however, give us a good idea of where radon levels are highest, which is also around the locations of the uranium mines towards the north and center of the US.

Check out how to use the shape map visual and the Mapbox custom visual in the Data Dashboards in Power BI course as well!

Power BI Weekly

One of the most recent videos in my Power BI Weekly series focuses on some neat tricks we can try out in the built-in shape map visual (a standard visualization currently in preview mode). In this lesson, I show how to take an existing outline of geographical areas and use the Mapshaper editor to combine the boundaries into new geographical areas. We can then export this custom JSON file to use as a custom map in this visual.

There are a few different ways to obtain shapefiles for maps, including through the section for these options on the US Census website.

Learn more about mapping!

One of the best parts of the LinkedIn Learning community is the opportunity to connect with and learn new things from fellow instructors. Gordon Luckett, for example, creates courses focused on GIS mapping systems. Here are two of his courses to check out! ArcGIS Pro is a subscription service, while QGIS is a free mapping tool to use.

Still to come in upcoming editions of this newsletter include neat tricks for calendar visuals, error bars, play buttons, and page optimization for Power BI model metrics. Stay tuned for what's to come!

-HW