Geographers emphasize spatial patterns, which are the general arrangements of things being studied and the repeated sequences of events, or processes, that create them. Learning to recognize and use geographical patterns is a fundamental skill in understanding the discipline. One of the most important tools of geographers are maps. Improvements in geospatial and computer technologies have dramatically increased the quality of maps, the accuracy of data, and the variety of maps available to study and use. Maps and geospatial data now influence everyday life with the use of smartphones and apps that allow us to not only view maps but interact, modify, and show our own location within the map.

Maps

Maps are the most important tool of a geographer and help to organize complex information. No tool communicates spatial information more effectively than a map. Maps are essential in highlighting and analyzing patterns. There are two broad categories of maps: reference maps and thematic maps:

Reference Maps

• Reference maps are aptly named because they are designed for people to refer to for general information about places.
• Political maps show and label human-created boundaries and designations, such as countries, states, cities, and capitals.
• Physical maps show and label natural features, such as mountains, rivers, and deserts.
• Road maps show and label highways, streets, and alleys.
• Plat maps show and label property lines and details of land ownership.

Thematic Maps

Thematic maps show spatial aspects of information or of a phenomenon. Following are descriptions of four common types of thematic maps.

Choropleth maps use various colors, shades of one color, or patterns to show the location and distribution of spatial data. They often show rates or other quantitative data in defined areas, such as the percentage of people who speak English.

Dot distribution maps are used to show the specific location and distribution of something across a map. Each dot represents a specified quantity. One dot might stand for one school building or for millions of people who own dogs. While these maps are known as dot distribution maps, any kind of symbol—a triangle, the outline of a house, a cow—can be used instead of dots.

Graduated symbol maps use symbols of different sizes to indicate different amounts of something. Larger sizes indicate more of something, and smaller sizes indicate less. These maps make it easy to see where the largest and smallest of some phenomena are by simply comparing the symbols to each other. The map key is used to determine the exact amount. The symbols themselves are arranged on the map centered over the location represented by the data, so they may overlap. Graduated symbol maps are also called proportional symbol maps.

Isoline maps, also called isometric maps, use lines that connect points of equal value to depict variations in the data across space. Where lines are close together, the map depicts rapid change, and where the lines are farther apart, the phenomenon is relatively the same. The most common type of isoline maps are topographic maps, which are popular among hikers. Points of equal elevation are connected on these maps, creating contours that depict surface features. Other examples of isoline maps are weather maps showing changes in barometric pressure, temperature, or precipitation across space.

In a cartogram, the sizes of countries (or states, counties, or other areal units) are shown according to some specific statistic. In the example below, the cartogram of world population shows Canada and Morocco as roughly the same size because they have similar populations (about 35 million people), even though Canada is more than 20 times larger in area. Any variable for which there are statistics can be substituted for the size of the country and mapped in the same way. Cartograms are useful because they allow for data to be compared, much like a graph, and distance and distribution are also visible, like on a traditional map.

Scale

Nearly every map is a smaller version of a larger portion of the earth’s surface. In other words, a map is a reduction of the actual land area it represents. Scale is the ratio between the size of things in the real world and the size of those same things on the map. A map has three types of scale: cartographic scale, geographic scale, and the scale of the data represented on the map. (See Topic 1.6 for more about scale.)

Cartographic scale refers to the way the map communicates the ratio of its size to the size of what it represents:

• Words: for example, “1 inch equals 10 miles.” In this case, 2 inches on the map would be 20 miles on the surface of the Earth.
• A ratio: for example, 1/200,000 or 1:200,000. This means that 1 unit of measurement on the map is equal to 200,000 of the same unit in reality. For example, 1 inch on the map represents 200,000 inches (or 3.15 miles) on the ground.
• A line: for example, the map may show a line and indicate that its distance on the map represents ten miles in reality. This is sometimes called a linear, or graphic, scale.
• Scale: Small-scale maps show a larger amount of area with less detail-global scale Earth at night is an example. Large-scale maps show a smaller amount of area with a greater amount of detail-North America at night is an example.

Types of Spatial Patterns Represented on a Map

Spatial patterns refer to the general arrangement of phenomena on a map. Spatial patterns can be described in a variety of ways utilizing important geographic tools and concepts including location, direction, distance, elevation, or distribution pattern.

Location

Locations may be absolute or relative. Absolute location is the precise spot where something is according to a system. The most widely used system is the global grid of lines known as latitude and longitude. Latitude is the distance north or south of the equator, an imaginary line that circles the globe exactly halfway between the North and South Poles. The equator is designated as 0 degrees and the poles as 90 degrees north and 90 degrees south.

Longitude is the distance east or west of the prime meridian, an imaginary line that runs from pole to pole through Greenwich, England. It is designated as 0 degrees. On the opposite side of the globe from the prime meridian is 180 degrees longitude. The International Date Line roughly follows this line but makes deviations to accommodate international boundaries. Thus, on this system, the absolute location of Mexico City is 19 degrees north latitude and 99 degrees west longitude.

Relative location is a description of where something is in relation to other things. To describe Salt Lake City, Utah, as being “just south of the Great Salt Lake and just west of the Rocky Mountains, on Interstate 15 about halfway between Las Vegas, Nevada, and Butte, Montana” is one way (of many) to describe its relative location. Relative location is often described in terms of connectivity, how well two locations are tied together by roads or other links, and accessibility, how quickly and easily people in one location can interact with people in another location.

Direction is used in order to describe where things are in relation to each other. Cardinal directions such as north, east, south, or west or intermediate directions such as southeast or southwest are commonly used to describe direction. On most maps, north will be the top of the map, but be sure to look on the map for cardinal direction clues.

Relative locations can change over time and as accessibility changes. For example, the many ghost towns (abandoned settlements) of the western United States once had relative locations near water sources (which dried up), along trade routes (which changed), or near mines (which closed). Their good relative locations lost the advantages of access to resources or trade that they once had. However, their absolute locations, as described by the global grid of latitude and longitude, remain the same.

Distance

Distance is a measurement of how far or how near things are to one another. Absolute distance is usually measured in terms of feet, miles, meters, or kilometers. For example, the absolute distance from home to your school is 2.2 miles.

The term relative distance indicates the degree of nearness based on time or money and is often dependent on the mode of travel. For example, traveling from home to your school takes 10 minutes by car or 25 minutes walking.

Elevation

Elevation is the distance of features above sea level, usually measured in feet or meters. The elevation of the summit of Mount Everest is over 29,000 feet. Elevation can impact a variety of things including climate, weather, and agriculture. Usually, the higher the elevation, the cooler the temperature gets and at very high elevations, it becomes more difficult for certain crops to grow. Elevation is usually shown on maps with contours (isolines).

Pattern Distribution

Geographers are also interested in distribution, the way a phenomenon is spread out over an area (L2). Essentially, distribution is a description of the pattern of where specific phenomena are located. Geographers look for patterns, or the general arrangement of things, in the distribution of phenomena across space that give clues about causes or effects of the distribution. Common distribution patterns include the following:

• Clustered or agglomerated phenomena are arranged in a group or concentrated area such as restaurants in a food court at a mall or the clustering of cities along the border of the United States and Mexico.
• Linear phenomena are arranged in a straight line, such as the distribution of towns along a railroad line.
• Dispersed phenomena are spread out over a large area, such as the distribution of large malls in a city.
• Circular phenomena are equally spaced from a central point, forming a circle, such as the distribution of the homes of people who shop at a particular store.
• Geometric phenomena are in a regular arrangement, such as the squares or blocks formed by roads in the Midwest.
• Random phenomena appear to have no order to their position, such as the distribution of pet owners in a city.

Projections

Because the earth is a sphere and maps are flat, all maps distort some aspect of reality. The process of showing a curved surface on a flat surface is done using a map projection. Cartographers decide whether they want to preserve area, shape, distance, or direction on their map accurately, knowing that other elements will have to be less accurate as the earth is “flattened” on their map. Essentially all maps are distorted, but cartographers use different maps for different purposes.

The Mercator, one of the most famous projections, was designed for navigation because the lines of directions are straight and easy to follow. A weakness of the Mercator on a global scale is that it makes the land masses appear larger than reality as you move north or south from the equator. This results in the countries of North America and Europe appearing larger and possibly more powerful than the countries near the equator. Greenland’s size on a Mercator looks to be the same size of Africa; however, in reality, Africa is 14 times the size of Greenland.

Geographers are concerned by the political and economic bias of power, wealth, and superiority that can be subconsciously reinforced by using an incorrect projection. All projections and maps have strengths and weaknesses. The key is to understand this and select the best projection for the map.