Cartography is the process of creating maps, and it’s used for far more than finding your way from one city to another. From urban development and military strategy to tracking climate change and visualizing election results, mapmaking serves as a fundamental tool for organizing spatial information and making decisions based on it. The global geographic information system industry was valued at $14.56 billion in 2025 and is projected to nearly double to $31.8 billion by 2031, reflecting just how central spatial mapping has become across industries.
Understanding what cartography is used for starts with understanding how maps are made and why specific choices in that process matter for different applications.
How Maps Are Actually Made
The cartographic process follows five core steps. First, the mapmaker defines the purpose of the map. A map designed to show flood risk in a coastal town serves a completely different goal than one showing population density across a country, and that purpose drives every decision that follows. Second, the mapmaker chooses the scale, which determines how much geographic area the map covers and at what level of detail. Third comes the practical format: print or digital, screen size, and production costs.
The fourth step is where things get interesting. Raw geographic data is far too detailed to dump onto a map at most scales, so cartographers abstract and generalize the information. This means selecting what to include, simplifying complex coastlines or road networks, and grouping smaller features into summary categories. The goal is to preserve the real geographic patterns while keeping the map legible. A highway map of an entire state, for instance, can’t show every residential street without becoming unreadable.
Finally, the cartographer designs the layout: choosing colors, symbols, labels, and visual hierarchy so the reader’s eye goes to the most important information first.
Generalization: Making Complex Data Readable
Generalization is one of the most critical skills in cartography because it determines whether a map actually communicates or just overwhelms. Several specific techniques make this work. Simplification strips away unnecessary detail while keeping essential shapes intact. Smoothing adjusts jagged geographic features (like a highly irregular coastline) into cleaner lines that still look realistic. Selection and omission decide what belongs on the map at all, based on the purpose and scale.
When features sit too close together at a given scale, cartographers use displacement or exaggeration to separate them visually so they remain distinguishable. Aggregation groups individual data points into summary categories. And classification assigns features to categories and represents them with symbols, like using a star for a capital city instead of drawing the actual city footprint. Every one of these choices introduces a small trade-off between precision and clarity, and the best maps find the right balance for their audience.
Map Projections and Their Trade-Offs
Every flat map distorts the Earth’s curved surface in some way, and the type of projection a cartographer chooses determines what gets distorted. This matters because different uses demand accuracy in different properties.
Equal-area projections keep the relative sizes of regions correct. If Brazil is 15 times larger than France on the globe, it will be 15 times larger on the map. These are essential for any application comparing quantities across regions, like deforestation rates or population density. The trade-off is that shapes get stretched or compressed, especially near the edges.
Conformal projections (the Mercator is the most famous) do the opposite. They preserve angles and local shapes, making them invaluable for navigation because a straight line on the map corresponds to a constant compass bearing. But sizes become wildly distorted: Greenland appears roughly the same size as Africa on a Mercator map, when Africa is actually 14 times larger. Conformality and equal-area accuracy are mutually exclusive. You cannot have both on the same map.
Equidistant projections preserve true distances, but only along specific lines radiating from one or two points. They’re useful for showing how far various cities are from a single location, like a radio transmitter’s range or airline routes from a hub airport.
Visualizing Data With Thematic Maps
Beyond showing where things are, cartography is used to show how much, how many, and how different. Thematic maps are the workhorses of data visualization, and each type suits a different kind of information.
Choropleth maps color entire regions (counties, states, countries) uniformly based on a data value. They’re the maps you see constantly in news coverage of elections, COVID rates, or income levels. They work best with derived values like percentages, rates, or densities rather than raw totals, and they’re effective because most audiences already know how to read them. Their limitation is that they can imply a phenomenon stops abruptly at a political border when it doesn’t.
Proportional symbol maps scale a symbol (usually a circle) to represent a quantity at each location. A city with 5 million people gets a much larger circle than one with 500,000. These handle datasets with a huge range of values well and work for both individual points and summarized regional data. They’re commonly used to map economic activity, earthquake magnitudes, or outbreak case counts.
Isoline maps connect points of equal value with contour lines, creating a smooth, continuous surface. Weather maps showing temperature zones or barometric pressure are classic examples. They naturally represent environmental phenomena like rainfall, elevation, or air quality because those variables change gradually across space rather than jumping at borders.
How Symbols Encode Information
Every symbol on a map communicates through a set of visual properties that cartographers manipulate deliberately. The French cartographer Jacques Bertin identified six core “retinal variables” that the human eye processes differently: shape, size, orientation, texture, hue (color), and value (lightness or darkness).
Size, value, and texture naturally suggest quantity. Your eye reads a larger circle as “more” and a darker shade as “higher intensity” without any explanation needed. Size works best for raw amounts (city population, total revenue), while value works better for relative intensity (percentage of residents below the poverty line, rate of infection per 100,000). Shape and hue, on the other hand, communicate qualitative differences: different colored dots might represent different crop types, or different icon shapes might distinguish hospitals from schools. Orientation is used most directly to show the actual direction of a feature, like wind arrows or river flow.
These aren’t arbitrary design preferences. They reflect how human perception works, and using the wrong variable for the wrong data type produces maps that mislead or confuse.
Military and Defense Applications
Cartography has shaped military strategy for centuries, and that relationship hasn’t faded with modern technology. Terrain, water features, atmospheric conditions, and other physical geography remain critical at the tactical level, influencing everything from troop movement to supply line planning.
Historically, military leaders were expected to be fluent in geographic analysis. Dwight Eisenhower, during his time at the Army War College, produced detailed military geography reports on the eastern United States and Mexico. When he arrived at the General Staff early in World War II, George Marshall tasked him with assessing the global situation with a focus on the Pacific. Eisenhower’s response, laid out in just a few pages, was built almost entirely on the military geography of the theater. The physical geography of the Pacific fundamentally shaped the why, who, when, and how of the joint campaigns that followed.
Today, geospatial intelligence remains a dedicated specialty within military organizations, using satellite imagery, digital elevation models, and layered spatial data to analyze terrain and plan operations at scales from individual buildings to entire regions.
Environmental Monitoring and Climate Tracking
Cartography gives scientists and policymakers a way to track environmental change over time and communicate it to the public. NOAA’s sea level monitoring system, for example, maps long-term sea level trends at more than 100 locations across the United States, using directional arrows to show whether local sea level is rising or falling at each station. Sea level has risen 8 to 9 inches since 1880, and the rate of increase has accelerated during the satellite era.
NOAA also offers an interactive sea level rise viewer that lets users visualize community-level impacts from coastal flooding at increments up to 10 feet above average high tides. This kind of tool translates abstract climate projections into something a homeowner, city planner, or insurance company can act on. Similar mapping tools track deforestation, wildfire risk, ice sheet loss, species habitat ranges, and air quality, turning raw sensor data into spatial patterns that reveal where change is happening fastest and where interventions are most urgent.
Urban Planning and Infrastructure
City and regional planners rely on cartographic tools daily. Zoning maps define what can be built where. Infrastructure maps track water lines, sewer systems, electrical grids, and transportation networks. Overlay analysis, where multiple data layers are stacked on a single map, lets planners see how proposed developments interact with flood zones, protected habitats, traffic patterns, and existing utilities simultaneously.
Digital mapping has made this process far more dynamic than it was with paper maps. Planners can model scenarios: what happens to traffic if a new neighborhood is built here, how stormwater runoff changes if this area is paved, where new transit stops would serve the most residents. These spatial questions are cartographic questions at their core, even when the tools involved are sophisticated software platforms rather than ink and paper.