Mapping 101: Your Cartography Crash Course
Welcome to Mapping 101, your cartography crash course. Maps are a beautiful balance between science and art, serving as both tools for navigation and mediums for storytelling. They play a pivotal role in our understanding of the world, providing insights into everything from geographic features to social dynamics.
Maps come in various forms, each designed to convey specific types of information. Physical maps, for instance, allow us to visualize the topography of far-off mountain ranges, showing elevations and natural features like rivers and valleys. These maps are essential for outdoor enthusiasts, geologists, and anyone interested in the physical characteristics of a region.
On the other hand, political maps highlight the boundaries and divisions between countries, states, and cities. They can also be used to illustrate demographic data, such as population density or religious breakdowns within a region. By providing context to political and cultural landscapes, these maps help us understand the complexities of human societies.
While the types of maps and their applications are nearly endless, most maps can be generalized as either a reference map or a thematic map.
Reference Maps
Reference maps, also known as general purpose maps, focus on the location of features like geographic boundaries, physical features, or cultural features like cities or roads. These maps are generally designed for people to learn general information about places. Typically, reference maps are things like:
Political Maps
Physical Maps
Topographic Maps
Political Maps
One of the most widely used reference maps, political maps focus on geopolitical elements. This is likely the first map you’ll be introduced to. It's the world map in your childhood classroom, or the Google map navigating you through cities. Political maps show administrative boundaries between countries, or states, and have information like the names of cities, roads, and highways. Occasionally, physical features like names of oceans, rivers, or mountains are included on political maps for geographical reference.
Non-negotiables
Clear labels: labels are one of the main focuses of political maps and should be accurately placed and easy to read.
Correct projection: a political map should accurately depict whichever area it’s focusing on, and the projection should align with the type of data displayed (more on projections further down).
Border styles: another huge focus of political maps, borders should be clear and easy to read.
Physical Maps
Also known as relief maps, physical maps show the natural features and landscape of the earth. Mountains, rivers, glaciers, deserts, and valleys (and more) are depicted on physical maps, helping to visualize the natural terrain of the earth's surface. Sometimes political boundaries are represented on physical maps to help increase the utility of the map, but this is not the focus.
Non-negotiables
Projection aligns with the purpose of the map: Ensure the projection aligns with the purpose of the map. For physical maps, projections that preserve area (equal-area projections) are often preferred.
Consistent and Clear Scale: The scale should be appropriate for the level of detail needed. Large-scale maps (e.g., 1:10,000) show more detail for small areas, while small-scale maps (e.g., 1:1,000,000) cover larger areas with less detail.
Geographical Names: Important places, landforms, and water bodies should be clearly labeled.
Comprehensive Legend: Explains all symbols and colors used on the map, such as those representing different types of terrain, vegetation, and water bodies.
Source: GISGeography
Topographic Maps
Topographic maps provide a detailed view of the landscape, displaying contours, elevations, forest cover, marshes, pipelines, power transmission lines, buildings, and various boundary lines, including international, provincial, and administrative borders. They also feature a Universal Transverse Mercator (UTM) grid, enabling users to pinpoint exact locations. Essentially, topographic maps transform a three-dimensional landscape into a two-dimensional format for easier visualization.
Non-negotiables
Contour Lines: While other maps might depict elevation with shading or color, contour lines are unique to topographic maps. They show the precise shape and elevation of the terrain, allowing users to understand the topography and slope of the land.
Contour Intervals: The specific distance between contour lines, which is consistent throughout the map, is crucial for determining the steepness of slopes. This interval is a unique feature that allows for detailed analysis of terrain.
Elevation Markers: Spot elevations or benchmarks are often included to give specific height information at particular points.
Grid System for Precise Location: Although other maps may use coordinate systems, the specific use of a Universal Transverse Mercator (UTM) grid is common in topographic maps for precise positioning and navigation.
Source: OpenTextBC
Thematic Maps
Thematic Maps are less grounded in physical or geographic locations and focus more on patterns or themes (hence the name) across a geographic area. While useful in certain regards, thematic maps will not help you navigate a busy city or tell you what the capital or Argentia is. Weather reports, birth rates, literacy rates, or income rates are among the types of patterns featured on thematic maps. Thematic maps are usually based on statistics and help visual spatial data, bridging the gap between graphs and maps. The first ever thematic map was created in 1607 by Jodocus Hondius called the Designatio orbis christiani which showed the distribution of world religions.
There are many different types of thematic maps:
Choropleth Maps
Dot Density Maps
Isoline maps
Graduated symbols
Choropleth Maps
Choropleths are the most common type of thematic map. Choropleth maps use different shades of colors to represent variations in features or patterns. Data is organized into distinct classes or ranges, and each range is given a color to represent it. A color is then assigned to a geographical area to represent the correct correlation to the data. Hence, choropleth maps are often accompanied by political boundaries to help present more accurate data. Color-coded geographic areas make it easier to analyze data across locations, and tell a story of what the distribution of data means for that area.
Non-negotiables
Make sure your data is attached to the same geographic unit (for the GIS techies, enumeration areas need to be the same!)
Data should be processed (converted into ratios, rates, or percentages) do NOT use raw data. This helps ensure fair comparisons. For example, population data might need to be adjusted per capita to make it comparable across regions of different sizes.
Data needs to be applied to the whole area of study (in GIS tech speak: continuous statistical surface)
Here’s a nice example of a choropleth map showing the unemployment rate by state in 2012.
Detail Detour
Before we move on, let’s take a quick break to go over map projections, and why they are important.
Map projection is the method of taking the curved, three-dimensional, spherical surface of the earth, and turning it into a two-dimensional, flat, representation usually on a screen or piece of paper. As you can probably imagine, this isn’t the easiest process and is the reason why no projection can preserve all property attributes (distortion, accuracy, and aesthetics). Some projections focus on maintaining accurate area while others will preserve shapes or distances and directions. A good rule of thumb to remember is that across all projections, features (typically near the edges) will get more and more distorted the bigger the area you are looking at.
See these examples between the most popular projection map, the Mercator projection which uses a cylinder projection, making Greenland and Antarctica look much larger
Depending on which metric property the projection preserves, they are classified as follows:
Conformal: preserves the shapes and angles of small areas, making this projection popular for directions. Examples include Mercator, Lambert Conformal Conic.
Equal-area: preserving area measure, but distorting shapes in order to do that. (ex. Eckert IV, Sinusoidal and Mollweide projections.
Equidistant: preserving distance between two points. An example is the Plate carrée projection.
Compromise: This projection strives to find a balance between preserving all the properties. Aka: does nothing perfect but does most things well enough.
Maps are typically projected onto either a plane, a cone, or a cylinder.
A flat plane produces azimuthal projections. Also known as zenithal projections, this form of projection is more accurate for polar regions and preserves global directions.
Azimuthal projections are further broken down into specific perspectives including orthographic, gnomonic, and stereographic.
A conic projection uses an unwrapped cone shape to project the surface of the earth. These projections keep distortion constant between parallels. A popular conic projection is the Albers projection which is an equal area projection - what you’ll need for a dot density map.
Finally, there is the cylindrical projection which tends to be most accurate around the equator. One of the most famous cylindrical projections is the Mercator projection, which was a revolutionary map when it was created in 1569 and is still one of the most widely used and recognized projections today.
Gerardus Mercator created this map to help sailors navigate, by allowing them to draw a straight line on their maps to represent their path. This projection is particularly useful for navigation because it gives accurate directions and preserves angles. However, as with all projections, the Mercator projection is not without its faults. As with most cylindrical projections, the distortion gets quite significant the further away from the equator you get. The Mercator projection makes it seem like Greenland and Africa are around the same size, but in reality, Africa is 14 times bigger than Greenland.
See the image below, the light blue is how countries appear on the Mercator projection, with the dark blue representing their accurate sizes. If your mind is blown with the true size of Greenland or Antarctica don’t worry, you’re not alone.
Antarctica is actually this small and this shape, but the maps we are used to blow it up to make it seem like a vast icey wasteland, when in fact it’s only the 5th largest continent, and is just slightly bigger than Australia.
One of the most accurate maps preserving actual size is the AuthaGraph Projection, invented in 1999 by an architect, Hajime Narkukawa. This map is still imperfect, but it won him the Good Design Award in 2016. However, because it still requires a few tweaks before it becomes an area-equal map, it is still a proprietary model and cannot be reproduced quite yet, or used in GIS software. But, it’s getting close!
Ok, now that we have a grasp of map projections, let’s get back to our regularly scheduled programming.
Where were we…
Dot Density Maps
As the name suggests, dot density maps are an effective way to visualize density differences across locations. They have been around for more than 100 years because they are easy to understand at a glance, conveying the results of the data in a digestible format.
Non-negotiables
Must be drawn on an equal area map projection - not preserving the size of the areas can distort how the density of dots is perceived. Equal area projections are important because they preserve the real area of features even if they distort shapes or angles.
Dot density maps are useful because they work with raw data, in black and white, and do not need to be represented in enumeration units (unless, of course, the data is reported by enumeration units—in which case you’re probably stuck with them).
Isopleth Map
Isopleth maps use lines to represent equal values, kind of like how choropleth maps use colors. But instead of sticking to predefined boundaries like political borders, isopleth maps connect points of equal value with contoured lines and are not restrained to political boundaries. This approach highlights where data values change, which is super handy for large-scale analyses of continuous data like weather patterns, temperature, or elevation.
However, this has its pros and cons. Since they're designed for continuous data, they don't handle abrupt or irregular changes well. So, if you're dealing with data that has sudden shifts or atypical results, isopleth maps might not be your best bet.
Non-negotiables:
Accurate Continuous Data: Isopleth maps need continuous data that's accurate and evenly spread out. This is crucial for creating meaningful and correct contour lines.
Consistent Intervals and Clear Labels: Make sure the intervals between contour lines are consistent and clearly defined. Labels and a comprehensive legend are a must for easy reading.
Proper Interpolation: Use the right interpolation methods to estimate values between measured points. This ensures your contour lines genuinely reflect the data.
Graduated Symbols Map
Graduated symbol maps use symbols of varying sizes to represent data values. The size of each symbol corresponds to the magnitude of the data it represents, making it easy to compare different values at a glance. These maps are particularly useful for showing quantitative data like population, economic activity, or other countable items across different regions. They provide a clear visual comparison without relying on color variations or boundary lines.
Non-negotiables
Clear and Distinct Symbols: Symbols should be distinct and easily distinguishable from one another. Overlapping symbols should be minimized to prevent confusion and ensure clarity.
Appropriate Legend: A clear and comprehensive legend is essential. It should explain the relationship between symbol size and data values, making it easy for viewers to understand the map.
Here is a graduated symbol map showing the number of sheep in Wales using data from 2015.
Although all the maps I mentioned are used differently, there are a few things that ALL maps should have in common. At their core, certain features are non-negotiable when it comes to creating an effective and visually appealing map. These essential elements include clear and concise titles that immediately inform the viewer of the map's purpose, well-designed legends that decode the symbology and color schemes used, accurate scales that provide a sense of distance and proportion, and directions that orient the viewer properly. These components are critical because they can make or break a map when it comes to aesthetics and comprehension.
Even with robust and reliable data, a poorly composed map can lead to confusion, misinterpretation, or even misrepresentation of the information. It’s not just about what data is presented, but how it’s presented. Clarity and precision in map design ensure that the information is conveyed accurately and effectively, enhancing the user's ability to understand and utilize the data.
If you're interested in delving deeper into the intricacies of what makes a map truly great, check out our other blog post, What Makes a Great Map. In this post, we explore various elements and best practices in detail, offering insights and tips to help you create maps that are informative, easy to understand, and aesthetically pleasing.
Want to put some of these tips into practice? Create a reference map using Nova!
Thanks for reading!
Kasha + the Nova team
