In today’s context it is bit of a challenge writing a post about the authoritative bias of maps. After all, how can maps be both accurate and tendentious. Kuby, Harner, and Gober’s book Human Geography in Action (Amazon Link: this authoritative bias to five critical decisions cartographer must make in creating and conveying visual information: maps projections, simplification, map scale, aggregation, and type of map.[1] Below are a couple of ways Google’s Geo tools can be used to demonstrate these choices.

1. Maps Projection

As discussed in a previous post (link), Google Maps, Google’s Maps API, and Google’s My Maps uses a Mercator projection. Projections are chosen for a purpose; in this case probably navigation. The easiest way to demonstrate the impact of this choice simply draw the ring around Greenland in My Maps, or, and drag the polygon to the equator. I normally show this in class then give the student 20 – 30 mins to draw and drag polygons. Students tend to want to know the size of Russia and like to drag the continent of Africa north towards the pole. Being from Texas, I often ask students to grab Alaska and bring it south over the continental US for a bit of humbling.

Map Projection

Map Projection My Maps

Map Projection Cool Site

2. Simplification

Kuby et al. like to use subway maps to demonstrate the idea of simplification and its benefit to the user. Below are London’s transit tubes on Google Maps and the other is London’s transit tube map. Explore and follow routes through London by zooming in/out and dragging the two maps below. Imagine if you where actually in London. Which map is more useful if you need to use this transit system? Which map is more accurate?

(Sorry, Google’s API only shows tube transit lines from this zoom level and closer)

Source: Google Maps API Transit

Use the slider at the bottom of this map to help compare.

Source: Transport for London

Simplification Google Earth


3. Map Scale

The zoom level of a map corresponds with the detail of a map.  Large scale map views a smaller area with more detail. Small scale maps view a large area with less detail. Which maps below gives you more detail of Texas’ Capitol?

Map Scale Google Earth

Map Scale

4. Aggregation

Aggregation is the size of geographic units in visualized in the map. The video below shows how level of aggregation tells a different story for Pennsylvania’s 2016 election. The end of the story is the same but rescaling the data tells a richer story.

Aggregation (State Result vs. County Results) Google Earth

Aggregation (State Result vs. County Results)

5. Type of Map

Be it reference or thematic maps, cartographers still must make decisions on what to show, omit, or emphases.

Reference maps: See what Google Maps can do depending on your search location setting. If you do this make sure you set your location setting back. (Developer Maps API Link Localization)

Thematic Maps: Here is a simple change in shading created to complicate the spatial distributions of Pennsylvania’s 2016 election votes. (Initial Blog Post Here)

Shading Thematic Maps Google Earth

Shading Thematic Maps

KML Files (Add to your drive or download): 

Kuby, Harner, and Gober’s book Human Geography in Action (Amazon Link: is much richer than this simple post.  I highly recommend this text for anyone, or class, that wants to deepen their knowledge of geography. The intent of this post is to show the purposeful inaccuracy of maps and the importance of these inaccuracies. While maps, and many other forms of information, can be misleading, it is not always for nefarious reasons.  At some point, the read/user has assess the value and limitations of their sources. The primary purpose of a map is often to transfer information more efficiently than a textual source.  After all, as Harm De Blij wrote, “If a picture is worth a thousand words, a map is worth a million.” Try it yourself…describe the boundaries of all the countries in the world. Don’t forget the disputed ones. The choices made by cartographers give maps both value and limitations.

[1] Kuby, Michael, John Harner, and Patricia Gober. Human Geography in Action. 6th ed. Hoboken, NJ: John Wiley and Sons, 2013.

Voting Data Sources:
Pennsylvania Spatial Data Access: (Download County Boundaries – Almost every state has this…Census also has state counties

Pennsylvania Department of State: (Election Data)