The term cartography is derived from the Greek words chartis (map) and graphein (to write). Cartography is commonly defined as the art and science of mapmaking, although these dimensions are not mutually exclusive. The “art” component of cartography refers to the aesthetic or design aspects of maps and mapmaking. Similar to artwork, each map is unique, and maps may be critiqued similarly to pieces of art. An artistic step in the mapmaking process includes the creation of an overall design layout for a map. The “science” component of cartography refers to the science and mathematics necessary for accurate and effective map production. Examples of the science aspect of cartography include the use of map projections to transform the spherical surface of the Earth to a flat map and the development of an experiment with human participants to determine which color combinations on a map are perceived most effectively. A person who compiles, designs, and produces maps of any type is referred to as a cartographer. This entry describes the types of maps and the variety of ways in which they are used and provides a brief history of Western cartography. It then reviews the elements of maps and explains the steps involved in creating them. In exploring how map users perceive and interpret maps, cartographers have conducted research in the areas of perception and cognitive studies. These studies, along with technological innovation, have led to a variety of new applications of cartography in today's world. The entry examines some of these advances and concludes with comments on the cultural and ethical issues associated with cartography.
Throughout human history, maps have been created for a variety of uses and purposes. One of the earliest uses of maps was for navigation or wayfinding purposes, and this remains a common use of maps today. For example, a nautical chart used by the crew of a ship for navigation by sea and a subway map used by a tourist to travel around a city are both examples of maps used for navigation purposes. In addition, maps are commonly employed for displaying or visualizing geographic trends or patterns in data. For example, a map of population density for provinces in a country would display geographic patterns of high- and low-density population in the country. Some maps depict geographic change over time, such as weather maps on television that forecast trends in daily temperature change over a week for a location. Other maps are used primarily for the management of resources, for example, maps used by employees of a city to manage infrastructure such as utility or water lines. Maps are also commonly used to assist in the decision-making process, such as a map that displays possible building locations for a new business based on proximity to prospective customers.
Maps produced by cartographers may be categorized in many different ways depending on their purpose or use. One common classification is to divide maps into two categories, reference maps and thematic maps. Reference maps (Figure 1) display the location of major geographic features such as cities, political boundaries, transportation networks, or physical features (e.g., rivers, lakes, and mountain ranges). Examples of reference maps include the topographic maps published by the U.S. Geological Survey and the British Ordnance Survey. Thematic maps (Figure 2), commonly referred to as statistical maps, display a particular theme, topic, or attribute. Examples include a map of per capita income for states in the United States and a map of languages spoken in countries within a region of the world. Thematic maps are constructed from a base map (e.g., state boundaries) and thematic or statistical data (e.g., per capita income for each state). Maps may also be classified in any number of other ways, such as by specific theme or topic, map scale, time period, or geographic area.
The earliest known maps that survive are in the form of paintings, drawings, or engravings on cave walls, clay tablets, animal hides, or parchments in ancient and indigenous civilizations. A painting of a village on the wall of a cave discovered in Catal Huyuk (modern Turkey) from the 7th century BC is widely regarded as the earliest known map. Babylonian maps dating to the 4th and 5th centuries BC depict the layout of ancient cities and the location of geographic features such as rivers and hills. The ancient Greeks (4th century BC) contributed several important advancements to cartography. For example, Eratosthenes (276-195 BC) devised a method of measuring the angle of the sun that he used to estimate the circumference of the Earth to within 100 miles of its actual circumference. The Greek geographer Claudius Ptolemy (AD 90-168) published several maps in his eight-volume Geographia, including a world map with lines of latitude (parallels) and longitude (meridians) clearly indicated. Ptolemy and the Greeks also devised a number of map projections, some of which are still in use today.
Mapmaking during the Roman Empire focused on cadastral or property ownership maps that were used for tax assessment purposes by the Roman emperors. A prominent example of a Roman map is the Peutinger Table, a map of the road network that connected territories administered by the Roman Empire.
The Middle Ages were characterized by mappae mundi, including T-O maps (named for their depiction of an O-shaped world divided into three continents by rivers and seas that form a “T”), which incorporated Christian doctrine and world-views into maps of the world. As coastal exploration of the Mediterranean increased during the 13th century, Portolan charts emerged to display the location of coastal ports and cities.
Several important advancements were made in cartography during the Renaissance. Prince Henry the Navigator (1394-1460) established a center for cartography in Portugal; seafaring European nations sponsored explorations around the globe during the Age of Exploration, beginning in the 15th century. In 1569, the Dutch cartographer Gerardus Mercator (1512-1594) introduced a map of the world based on a new map projection that would bear his name and would prove invaluable for sea navigation. The Dutch cartographers Abraham Ortelius (1527-1598; see Figure 3) and Jodocus Hondius (1563-1612) published the first modern atlases of the world based on the geographic discoveries of the Age of Exploration.
Thematic mapping arose in the 18th century and accompanied the rise in national censuses and statistics collected by government organizations. In the United States, the academic study of cartography in universities developed in the early part of the 20th century and accelerated following World War II.
Regardless of the type of map created by the cartographer, all maps are reductions and generalizations of the Earth. The map scale, which may be expressed on the map as a representative fraction (e.g., 1:24,000), as a verbal statement (e.g., “one inch represents two miles”), or as a graphic known as a bar scale, indicates how much the Earth has been reduced to fit on the map. The map scale influences the size of the geographic area displayed on the map as well as the amount of detail that may be displayed. Large-scale maps are those that display a relatively small geographic area but may display much detail. For example, a map of a city is a large-scale map that displays a relatively small geographic area but in much detail, with the inclusion of features such as streets, bus stops, and points of interest. In contrast, a small-scale map displays a larger geographic area but with less detail. For example, a map of a country or continent is an example of a small-scale map.
Generalization is the process whereby the cartographer selects the appropriate amount of detail to display on the map according to the map scale and the purpose of the map. An example of generalization would be the selection of cities with population figures above a certain number or the simplification of the appearance of a river by eliminating the smallest bends. Coordinate systems are necessary in mapmaking for plotting accurately the location of geographic features on the map. A coordinate system defines an x (horizontal) and y (vertical) coordinate that is referenced to the Earth's surface and then may be displayed on a map. Latitude and longitude is an example of a coordinate system that is used commonly in mapmaking.
A common challenge in cartography is the transformation of the mostly spherical Earth on a flat map surface. This challenge is overcome through the use of a map projection, a geometric or mathematical transformation of the Earth from a three-dimensional (3D) to a 2D surface. Hundreds of map projections have been developed to date, yet only a small number are used commonly in mapmaking today. Due to the necessity of depicting the mostly spherical Earth on a flat surface, every map projection distorts at least one of the following: area, angles, distances, or directions. Equivalent or equal-area map projections preserve the relative sizes of landmasses displayed on the map, whereas conformal map projections preserve the angular measurements. Equidistant map projections preserve the distance measurements between two points on the map, whereas azimuthal projections preserve the measurements of direction between two points. The selection of an appropriate map projection is an important step in mapmaking, and the purpose of the map often influences the type of map projection that is chosen. For example, a cartographer would choose an equivalent map projection for a map intended for comparing the size of countries or continents.
A cartographer follows a series of steps for producing a map—these steps are commonly referred to as the cartographic or mapmaking process. Typically, the first step is envisioning the goal or purpose of the map and identifying the map's intended audience. The type of map (e.g., paper for printing or digital for display on a computer) and format (or size of the map) are also determined by the cartographer at an early stage. A suitable map projection is selected, and all data are added to the map. Any additional data that are presented on the map must also be gathered. Sources of data for maps may include other maps, statistical data (e.g., population data), aerial photographs or satellite images, archival data, or field surveys.
Once all the data have been gathered, the cartographer must decide how to represent or symbolize the data on the map. Geographic features on maps are represented as either points (e.g., a city), lines (e.g., a river), or areas (e.g., a country). Each geographic feature is represented or symbolized with graphic variables, known as the visual variables, such as color, value, size, texture, pattern, or shape. If the map is a thematic map that displays quantitative data, several types of symbolization are possible that the cartographer may choose from, depending on the characteristics of the data. For example, choropleth maps depict data by symbolizing each enumeration or area unit with a shade of a color that represents a defined range or class of data. A graduated or proportional symbol map depicts quantitative data with symbols such as circles or squares that are sized according to the data value at each location on the map, as in Figure 2. Once a method of symbolization is chosen, the overall design of the map is clarified. The objective is to create a map that is balanced, harmonious, and aesthetically appealing to map users. Map elements such as a scale, title, legend/key, and north arrow are added to the map, each positioned to give an appealing appearance to the map.
After a completed draft of the map is produced, it is common for the cartographer to request feedback from typical users of the map. An important goal of the cartographic process is to determine if a given map communicates effectively or not. Feedback is used by the cartographer to improve the map, if necessary, prior to final production or distribution. Such feedback may be collected in a variety of ways, using both formal and informal methods. Formal methods of feedback may include structured interviews, focus groups, or questionnaires conducted with typical users.
Cartographers are keenly interested in how map users interpret, perceive, and remember information presented on maps, and for this reason, cognitive science is commonly integrated into cartographic research. In particular, cartographers study the perception (the processes associated with how humans process and interpret vision and other sensory information) and cognition (the processes associated with human thought and memory) of maps through structured experiments. In his book The Look of Maps (1952), the American cartographer Arthur Robinson established the foundation for a scientific approach to the study of map design and called for perceptual and cognitive studies in cartography to ensure effective map design. Such perceptual and cognitive studies have focused on numerous topics related to maps, such as the estimation of the sizes of map symbols (e.g., proportional circles, text, etc.) or the memory or recollection of geographic patterns displayed on thematic maps. Typically, such studies have been conducted in carefully controlled laboratory experiments. Such experiments may include the use of eye-tracking instruments that record data about what people look at on maps and how much time they spend viewing various aspects of the map. Collectively, the results from such perceptual and cognitive research help cartographers understand how people interpret maps and may be used to create better guidelines for making maps.
Technological change and innovation have had an important influence on the development of many aspects of cartography, from the earliest days of mapmaking to the present. Technological change has affected both the type of instrumentation used in the compilation of maps by cartographers and the means of reproducing or disseminating maps to others. For example, the invention of celestial instruments such as the sextant and astrolabe allowed cartographers to plot latitude coordinates on maps and nautical charts more accurately. The magnetic compass, theodolite, and other surveying instruments improved the positional accuracy and geometry of features on maps. The development of the printing press in the 15th century was an important innovation that allowed for the mass production of maps. The technology used for printing maps has evolved from methods such as engraved plate printing to lithography to digital printing today.
The computer revolution has had a significant impact on mapmaking by transforming maps into a digital medium and automating many steps in the cartographic process. Digital maps may be displayed by map users on personal computers or portable electronic devices such as cellular phones or car navigation systems. Global positioning system (GPS) technology has revolutionized mapmaking through increased accuracy and precision of the coordinates that are displayed on maps. The development of the World Wide Web (WWW) has created a new method for distributing and viewing maps; Web-based maps may be either static maps that may be viewed on a Web page or interactive/dynamic map displays. In addition, the WWW has provided a framework for easy distribution of data that may be used for the creation of maps. Advances in aerial photography and satellite imagery have had implications for cartography as well, as these both serve as important data sources that are often used in the compilation of maps.
Although maps have been compiled by hand-drawn or analog techniques for many centuries, modern cartography is almost entirely digital in nature and is completed with the assistance of computers. Geographic information systems (GIS), graphic illustration, and computer-aided drafting (CAD) software are commonly employed by cartographers for map production. An impact of the computer revolution in cartography is what Morrison (1997) described as the “democratization of cartography,” which is the increased production of maps by those with little or no cartographic training due to the easy availability of computer software that may be used for map production purposes.
The term geovisualization refers to interactive or dynamic maps that are developed today, such as those on Web sites that allow a user to change the appearance of features that are displayed on the map. For example, an interactive map may allow a map user the option of zooming in/out, modifying the colors displayed on the map, or changing the method by which data are symbolized on the map. Animated maps are a common method for displaying geographic change over time on maps. Data exploration mapping software is used to extract geographic patterns from large data sets that may involve the comparison of multiple variables on the map. As computer graphics technology has improved, so has the capability of cartographers to create 3D and virtual reality map displays that depict a more realistic representation of the Earth. As more focus is placed on the use of interactive and dynamic maps due to the technological changes in cartography, much attention has been focused on the design of the user interfaces and understanding how people interact with such displays.
Since maps are used by many people for different purposes, there are a number of social, cultural, and ethical issues related to map production and use. Historically, maps have been produced primarily by those with political power or influence and, therefore, may intentionally or unintentionally express the views or opinions of the mapmaker. Cartographic ethics calls for the accurate presentation of information on maps; however, maps may misrepresent the real world as a result of error or carelessness by the cartographer. The increased availability of highly detailed, Web-based maps and satellite imagery, used for applications such as navigation or real estate purposes, has raised privacy issues in recent years. A cultural issue related to mapmaking includes human interpretation of colors and symbols on maps, which may have various meanings or connotations in different cultures.
Argumentation maps, Cartograms, Cartography, History of, Choropleth Maps, Color in Map Design, Coordinate Geometry, Coordinate Systems, Coordinate Transformations, Countermapping, Dasymetric Maps, Data Classification Schemes, Datums, Dot Density Maps, Dynamic and Interactive Displays, Earth's Coordinate Grid, Ecological Mapping, Electronic Atlases, Environmental Mapping, Exploratory Spatial Data Analysis, Flow Maps, Gazetteers, Indigenous Cartographies, Isopleth Maps, Land Use and Land Cover Mapping, Latitude, Longitude, Map Algebra, Map Animation, Map Design, Map Evaluation and Testing, Map Generalization, Map Projections, Map Visualization, Mental Maps, Multimedia Mapping, Portolan Charts, Resource Mapping, Self-Organizing Maps, Trap Streets, Typography in Map Design, Virtual and Immersive Environments, Virtual Globes
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