Reference Maps

"You just make maps, right?" People who don't really know what geographers do (we suspect that's a lot of folks out there) usually do seem to know that cartography is centrally important to our trade. Where would we be without maps, anyway? Driving would certainly be messy, and let's not even talk about flying.

Mostly, what people are talking about are reference maps: the kinds with lots of features and colors, like the National Geographic map supplements that have come with the magazine for over a century, or those trusty road atlases that are still indispensable when there's no cell signal. Keep reading to learn more about different types of reference maps, some examples, and more.

Reference Maps Definition

A map, as you know, is a representation of spatial features at a smaller scale than reality. The scale of reality is 1:1, whereas a large-scale map might be 1:5,000 and a small-scale map of the world may be around 1:20 million or more at the Equator.

Maps don't have to be of the Earth, and they don't need to be two-dimensional, but for our purposes here, we will limit ourselves to those characteristics.

Reference Maps vs Thematic Maps

The other major type of map is the thematic map, which takes a certain characteristic or set of characteristics and spatializes it.

Reference maps can be historic, valuable, and beautiful, but thematic maps are often fun! (Think of the maps of language differences, such as the dominant terms used for soft drinks in the US.)

Besides their use as conversation starters, thematic maps can help us see spatial patterns in landscapes that we can't see in other ways. Weather maps, maps of deforestation in the Amazon, crime maps: all these are thematic maps and also powerful tools. So where does that leave reference maps?

Reference maps, in addition to being informative and helping up navigate or just learn about places, are also cultural artifacts. With time, they become historical artifacts that tell us a lot about what mapmakers (and their patrons) considered to be important and how they viewed the world.

References Aren't Always True

Reference maps can be political tools. Clever use of scale, projection, and other cartographer "tricks of the trade" can exaggerate the size of an area or diminish it, for example. Sensitive military installations can simply be left out. Disputed border regions can be claimed. Areas void of people can be filled in with unimportant features, just like blank expanses of the sea used to be labeled Here be Monsters.

What this means is that reference maps sometimes aren't so simple or even trustworthy. Indeed, as geographer Mark Monmonier has shown us, "how to lie with maps" comes with the territory, so to speak.¹

Types of Reference Maps

There are three broad types of reference maps.

Political Maps

These maps focus on political features as well as culture, population, and economic geography. They have few to no physical features but do include political boundaries and populated places. At a minimum, they label major political subdivisions such as countries, and may also label populated places such as cities. Maps with more details contain hierarchies of places with different symbols, hierarchies of political subdivisions, roads, and selected human-created features like National Parks, military bases, points of interest, and so forth.

Features such as a scale, orientation arrow (i.e., pointing "N"), title, legend, and projection types are also common, though not required to fit the definition of "political map."

Physical Maps

These are maps that focus mostly or entirely on the physical features of the Earth. They typically portray important physical geographic features such as rivers, lakes, mountain ranges, deserts, and so forth. Just as political maps often contain a few physical features, physical maps may portray scattered but minimal political features, such as a few populated places or the outlines of major political subdivisions.

Topographic Maps

"Topo" maps overlay topographic information on general maps. They help users visualize the Earth's surface in 3D by mapping elevation as well as latitude and longitude.

Topo maps are indispensable for any use where elevation difference is important, from road-building to hiking and from flood insurance to plant habitats.

Reference topo maps are often combined with thematic maps such that contour intervals (lines of equal elevation) become one of many different features. Often instead of contour intervals, a technique known as "hillshade" is used, which produces shaded relief maps where the different elevation levels are represented by distinct colors.

Fig. 1 - Topographic map that uses shaded relief (hillshade) to represent altitude above Earth's surface and depth of land below sea level

General Reference Maps

These are also known as planimetric maps. Notably, they do NOT include any topographic information such as contour lines or shading, though they may include notable elevations such as mountain peaks.

General reference maps combine physical and cultural features and serve as the base maps for thematic maps and for other reference maps. The governments of most major political subdivisions now maintain large geographic information systems (GIS) that contain all important spatial data organized into layers, making it possible to generate general reference maps with varying features. Google Earth is a good example of this. Google Maps and National Geographic paper maps provide users with pre-selected general reference maps.

Reference Maps Examples

Here are three examples of superlative reference maps from history.

The Oldest World Map?

Though older maps exist, the Imago Mundi or Babylonian Map of the World is the oldest surviving example of a reference map of the known world. In this case, it represents the world as known to the Neo-Babylonian people of Mesopotamia between 600 and 800 BC, written in Akkadian, in cuneiform, on a clay tablet.

This Babylonian view of the world was focused on, not surprisingly, Babylon itself, with the Euphrates River, some other cities, and surrounding world regions.

Fig. 2 - Imago Mundi

Eratosthenes, the Original Geographer?

Eratosthenes (276-194 BC) was a Greek scholar most famous for calculating the Earth's circumference. Though he practiced in many scientific fields of the time, geographers claim him as their own. His massive tome, "Geography," has been lost, but much of it was copied and reproduced by others.

His world map, reconstructed in 1883, showed a three-part world continent (Africa, Asia, Europe) and political as well as physical features known at the time. It also incorporated the parallels (lines of latitude) and meridians (lines of longitude) Eratosthenes derived from his measurements of our spherical planet.

Fig. 3 - Reconstruction of Eratosthenes' map

No One Greater than Mercator?

A candidate for "greatest map ever made" is that of Mercator. Gerardus Mercator (1512-1594) was a Flemish mapmaker who gave us the Mercator Projection that preserved equal direction and shape but distorted the size of land areas. The oceans of his 1569 world map are covered with rhumb lines that helped mariners calculate direction.

The large, book-like areas of text smack-dab in the middle of land and ocean areas are known as cartouches and include all sorts of information Mercator felt would be useful. Otherwise, what is immediately striking about the map is its inclusion of the Americas (all maps since the voyages of Columbus had this feature), the suspected southern continent, and a phantom continent encircling the North Pole. Mercator's concentration on physical and political features in the Old World and particularly Europe tells us about the geographic knowledge Europeans had at the time.

Fig. 4 - Mercator's 1569 world map Though there is no reason it should be so other than convention, north is at the top, and, as with Eurocentric maps in general, Europe is toward the center. The spherical world is split in the Pacific, far from Europe, rather than the Atlantic. Similar conventions tend to be found today on world maps.

One feature of the Mercator projection was its exaggeration of size. Though this is due to Mercator's goal of preserving orientation and shape, the distinction has been lost on many generations of schoolchildren and perhaps some of their teachers, as well.

Fig. 5 - Mercator projection

Beyond the massive distortion of Antarctica (which is why many maps using the Mercator Projection leave it off altogether), the misuse of the projection can make people unaware of the true size of northern places such as Greenland, Alaska, and Russia in comparison to regions like Africa. Because they are not taught that this projection distorts size, they may end up assuming that Greenland is larger than Africa in area, when in reality Africa is 14 times the size of Greenland.

Perceptually, this diminishes the importance of countries in Africa and elsewhere in the tropics, which often seem minuscule when in reality they are much larger than countries in, for example, Europe.