Aug 22, 2024
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Read this to learn how maps have been used historically and how they are used today, including how a map's scale controls the way it represents reality on a usable, two-dimensional surface.
The Basic Idea of Maps
The first thing to learn is how to read, use, and create maps. Your exploration of maps will be informed by understanding how maps reflect the relationship between space, society, and technology and how mapping is an essential form of scientific and artistic inquiry. You will also explore how mapping is used to address a variety of societal issues, from land-use planning and political gerrymandering to selling yogurt. You will gain insight into the technical underpinnings of mapping as a scientific approach. This lesson will introduce you to basic social and technical elements of maps, including a very short history of mapping.
The standard definition of a map usually revolves around the idea that a map is a spatial representation, usually on a flat surface, of an area. This definition is not very useful on its own, so in order to figure out what maps are about, people usually look at what maps do. In particular, maps
show an area larger than a person can see—most often this view is from above but not always present information concisely, especially the features of most interest to the user demonstrate spatial relationships show things people cannot see directly, such as minerals below ground or records of daily temperatures. It is also helpful to look at kinds of maps. There are two major kinds of maps: reference maps and thematic maps.
Reference Maps
Reference maps store data and show a variety of features for a variety of uses. These maps function like general storehouses of information. This is a reference map of China that stores a variety of information, including transportation routes, rivers, and names of water bodies.
An old map of South Asia and Southeast Asia created in 1856 shows important cities and sea routes labeled in German language. An 1856 general reference map shows Europe, Asia, northeastern Africa, and northern Australia. The map depicts the Indian Ocean and Pacific Ocean in a very pale blue color. The land masses are white with various black, blue, and red lines showing rivers and various transportation routes across Asia and across the oceans. The map has German text written on it. The German map title shown in a legend box in the bottom left corner of the map translates as "Research Trips in Asia in Medieval and Modern Times". Thematic Maps
Thematic maps highlight specific themes. Their chief goal is to focus the user's attention on specific features or characteristics. The next image has two thematic maps that each draw the user's attention to a single idea or theme. Any other information, such as the outlines of states, is provided only to help understand the main theme. In the next image, the map on the left is a categorical thematic map showing nominal classes of vegetation in 1974, and on the right, the map is a quantitative thematic map showing classes of population density in 1974.
Two maps of Thailand. The left map highlights the vegetation area, and the right map highlights the population of Thailand. Two maps of Thailand depicts categorical thematic map and quantitative thematic map, respectively. Regardless of whether a map is thematic or reference, it is essentially a technology that brings together knowledge from many fields. These include cartography, land surveying, remote sensing, computer science, information science, and social science. A map is also a social entity, in that society affects everything: data itself, how data is processed into information, and ultimately how information is turned into intelligence and used for action.
A Very Short History of Maps
The history of mapping is long, rich, and complicated. There are hundreds, if not thousands, of books on the history of mapping and maps. This is a very general outline that looks only at a few representations, primarily European and North American maps. In thinking about maps, it helps to distinguish between literal maps, which were meant to show actual things and places, and figurative maps, which show conceptual or imagined places.
Early Maps (25000 BCE+)
People have probably been scratching maps into the dirt with sticks for longer than they have been using words. The figure below shows a Babylonian map made around 600 Before Common Era (BCE) that traces relationships between cities and mythical places and ideas.
A world map is engraved on a rock. It has a double circle, some inscriptions, a few symbols, and a few shapes. A Babylonian world map and a few symbols engraved on a rock with a few cracks. Greeks (800–100 BCE)
The ancient Greeks produced fairly high-quality and accurate literal maps of the region around the Mediterranean Sea and were among the first people to discover Earth's circumference. Eratosthenes (276–195 BCE) is widely credited for this achievement. This map, The World According to Herodotus, is a reconstruction of the literal map that the Greeks produced of the Mediterranean Region.
A map of the world by Herodotus shows parts of Eurasia and northern Africa. A map of the world by Herodotus shows Europe, Asia, and part of Africa, specifically Libya. Medieval Maps (1100–1400s)
In Europe during the Dark Ages, maps took a turn toward the figurative, often in aid of advancing religious viewpoints of the world. An example is this "T and O Map," by Isidore of Seville, where the T is the Mediterranean, the Nile, and the Don Rivers dividing the continents of Asia, Europe, and Africa; and the O represents the encircling ocean. Given its religious significance, Jerusalem was placed in the center of the map and, because the sun rose in the east, Paradise (representing the Garden of Eden) was considered as being in remote Asia. This map captures aspects of reality, such as the relative locations of water bodies and continents, but this approach is a step back from past maps in terms of realism.
A map having two concentric circles with a T-shape at their center. Multiple foreign words are written in the map. A religious map by Isidore of Seville has the shapes T and O on it. At this time, non-European cartographers were developing literal maps. Al-Idrisi (1100–1165) was an Arab geographer, cartographer, and Egyptologist who lived in Sicily at the court of King Roger II. He traveled the Mediterranean and developed advanced maps of the world, like the one here.
A circular advanced map of the world by Al-Idrisi. Al-Idrisi's circular map of the world is the first map showing Europe, Asia, and northern Africa. Age of Exploration (late 1400s+)
European countries embarked on a period of exploration in the 1400s that reshaped the world. Many nations from around the globe had intrepid explorers before this time, but this period saw a rapid increase in maps being made for the explicit purpose of navigation. Chinese cartographers were developing maps for navigation but also as a way to understand history, as below, where Ch'üan Chin and Li Hui developed the Map of Historical Emperors and Kings and of Integrated Borders and Terrain.
A Chinese map depicting symbols and borders used for navigation. "Yoktae chewang honil kangnid, the “Kangnido” [Map of Historical Emperors and Kings and of Integrated Borders and Terrain]" by Ch’üan Chin [Kwon Kun] and Li Hui [Yi Hoe], myoldmaps.com is licensed under CC BY-NC-SA 4.0 The Cantino Map, shown below, is one of the earliest surviving maps showing Portuguese discoveries around the world. It is named after Alberto Cantino, who smuggled it from Portugal to Italy in 1502. The Cantino Map, like others of its kind at the time, held military, political, and economic significance. Given that such maps were being used to sail ships and lay claim to places, mapping became more concerned with providing literal and accurate representations of reality.
A map highlights several parts of the world with drawings of mountains, castles, trees, flags, and texts. The Cantino map depicting the military, political, and economic significance of the world. The map has several small compasses and a wind rose on it. Thematic Mapping (late 1600s+)
From the seventeenth century onward, more people made thematic maps. As discussed, thematic maps focus on a particular idea or theme, as opposed to serving multiple goals as a reference map. The 1837 map below shows travel flows out of Dublin and was one of the first maps designed to convey a sense of flow or movement, using the width of lines as proportional to the number of passengers traveling by rail.
A map of Ireland highlighting the movement of passengers through the railway from Dublin. A thematic map of railroad, or railway, traffic in Ireland in 1837. The thickness of the railroad corresponds to the amount of traffic, meaning, the thicker the line, the more traffic. This map was created to accompany a report submitted by the Railway Commissioners. Analytical Mapping (1800s+)
Related to thematic mapping is analytical mapping, where maps are used to explore the role of location and space to answer questions. One of the most interesting early examples of analytical mapping was the case of Dr. John Snow, an English physician. He investigated the outbreak of cholera in London in 1854. At the time, no one knew it was a waterborne disease. Snow spoke with residents and determined that many of the afflicted were drawing water from a public well in Broad Street. He established that people with the disease were clustered around the pump and convinced the authorities to discontinue its use. The Broad Street Pump is circled in red.
Snow is credited as being among the first scholars to consider how a spatial pattern could result from a specific process and to produce maps of his findings.
A map has several blocks and streets with names and a dot at the center that indicates the Broad Street Pump. John Snow's map indicating Broad Street Pump, from where cholera spread. Geographic Information Science (1960s+)
The advent of computing in the 1940s and 1950s led quickly to a foundation for the use of computers in mapping. The field concerned with this use of computers became known as geographic information science (GIS) and has become synonymous with mapping for many practitioners, although technically cartography is considered the art and science of making maps. (GIS can be used to make some truly terrible maps while a cartographer can make beautiful and useful maps using a variety of approaches.)
GIS, however, excels at bringing together many layers of data for a location and conducting a sophisticated analysis. These maps show attributes for part of the state of Wisconsin, United States. Geographic information systems are very helpful in that they allow investigators to store, manipulate, and analyze data on a large variety of phenomena.
Each map layer, used individually or in combination, represents geographical information about a piece of land. Seven different attribute data of the state of Wisconsin, depicting geographic information science. Scale
Scale and projections are two fundamental features of maps that usually do not get the attention they deserve. Scale refers to how map units relate to real-world units. Projections deal with the methods and challenges around turning a three-dimensional (and sort of lumpy) earth into a two-dimensional map.
So next, you will learn about scale and ways of telling the map user what the map is measuring on the ground; and projection mechanics, types of projections, and their characteristics.
Understanding Scale
The world is vast. The earth's surface has an area of over 500 million square kilometers and any picture of the earth that can be easily carried could only show general outlines of continents and countries. When a region of the world is represented visually on a map, its size must be reduced to fit in the boundaries of the map. Map scale measures how much the features of the world are reduced to fit on a map; or more precisely, map scale shows the proportion of a given distance on a map to the corresponding distance on the ground in the real world.
Map scale is represented by a fraction, graphic scale, or verbal description. For example:
Representative fraction scale: 1:62,500 Graphic scale: This image of a graphic scale shows visually that one unit (such as an inch) equals one mile. A graphic scale depicts a horizontal line labeled Miles with 6 markings in it. A graphic scale with 6 markings representing Miles is displayed. Verbal scale: Written out, such as "One inch equals one mile." Representative Fractions
The most commonly used measure of map scale is the representative fraction (RF), where map scale is shown as a ratio. With the numerator always set to 1, the denominator represents how much greater the distance is in the world. The next figure shows a topographic map with an RF of 1:24,000, which means that one unit on the map represents 24,000 units on the ground. The representative fraction is accurate regardless of which units are used; the RF can be measured as 1 centimeter to 24,000 centimeters, one inch to 24,000 inches, or any other unit.
A topographical map from 1929 shows the contour intervals for a section of Colorado. A topographical map labled Eldorado Springs shows contour intervals for a section of Colorado. Three scales show measurements in feet, miles, and kilometers, using data from 1929. The map is divided into four sections by vertical lines and the corresponding longitude and latitude are provided. Graphic Scales
Scale bars are graphical representations of distance on a map. The figure has scale bars for one mile, 7000 feet, and one kilometer. One important advantage of graphic scales is that they remain true when maps are shrunk or magnified.
Verbal Descriptions
Some maps, especially older ones, use a verbal description of scale. For example, it is common to see "one inch represents one kilometer" or something similar written on a map to give map users an idea of the scale of the map.
Mapmakers also use the term "scale" to describe maps as being small-scale or large-scale. This way of using the term "scale" as large or small can seem counterintuitive at first. Here is an example:
A map of the United States, sized three meters by five meters (about 9 by 15 feet) has a small map scale. Any given feature, such as a lake in Ohio, will be quite small at this scale. A university campus map of the same size (9 by 15 feet) is large-scale. A lake the same size as the Ohio one just mentioned would appear much larger on this map. The key factor here is the comparative sizes of the RF scales used to create each map. The width of the United States, from coast to coast, is about 3000 miles. Using a 15-foot-wide map to represent a 3000-mile (15,840,000 feet) distance creates an RF of about 1:1,056,000. If the university campus is 3 miles (15,840 feet) wide and is represented on, again, a 15-foot-wide map, the RF is 1:1056. Scale descriptions using the RF provide one way of considering scale, since 1:1000 is larger than 1:1,000,000.
When mapmakers talk about large- and small-scale maps and geographic data, then, they are talking about the relative sizes and levels of detail of the features represented in the data. In general, the larger the map scale, the more detail is shown.
Key Terms
reference maps: maps used to display important physical elements of a specific geographic area, such as countries, rivers, mountains, etc. thematic maps: specialized maps used to understand one particular attribute or characteristic of a specific geographic area; examples are population maps, weather maps, and maps illustrating the spread of disease literal maps: maps that strive to display the objective truth about a specific geographic area figurative maps: maps that use symbols to represent a narrative or point of view; they are much less concerned with physical accuracy than are literal maps analytical mapping: the use of cartography techniques to uncover and learn about patterns and trends in a specific geographic area map scale: how the measurement of distance on a map corresponds to the distance on the ground in the real world representative fraction (RF): a way of describing the scale of a map by using a ratio small-scale: a way of describing a map with a relatively small RF, where the various features of the geography appear relatively small large-scale: a way of describing a map with a relatively large RF, where the various features of the geography appear relatively large Attributions and References