What is a Map? - schroeppel-design.de · Early Maps Cartography is the art and science of making maps. The oldest known maps are preserved on Babylonian clay tablets from about 2300

Envisioning Information I · Markus Schröppel · 2009 37/62

What is a Map? A map is a graphic representation or scale model of spatial concepts. It is a means for conveying geographic information. Maps are a universal medium for communication, easily understood and appreciated by most people, regardless of language or culture. Incorporated in a map is the understanding that it is a "snapshot" of an idea, a single picture, a selection of concepts from a constantly changing database of geographic information (Merriam 1996). Old maps provide much information about what was known in times past, as well as the philosophy and cultural basis of the map, which were often much different from modern cartography. Maps are one means by which scientists distribute their ideas and pass them on to future generations (Merriam 1996). Early Maps Cartography is the art and science of making maps. The oldest known maps are preserved on Babylonian clay tablets from about 2300 B.C. Cartography was considerably advanced in ancient Greece. The concept of a spherical Earth was well known among Greek philosophers by the time of Aristotle (ca. 350 B.C.) and has been accepted by all geographers since. Greek and Roman cartography reached a culmination with Claudius Ptolemaeus (Ptolemy, about A.D. 85-165). His "world map" depicted the Old World from about 60°N to 30°S latitudes. He wrote a monumental work, Guide to Geography (Geographike hyphygesis), which remained an authorative reference on world geography until the Renaissance.

Ptolemy's map of the world, about A.D. 150, republished in 1482. Notice the use of latitude and longitude lines and the distinctive projection of this map. Taken from Whitfield (1994, p. 8-9).


Medieval Maps During the Medieval period, European maps were dominated by religious views. The T-O map was common. In this map format, Jerusalem was depicted at the center and east was oriented toward the map top. Viking explorations in the North Atlantic gradually were incorporated into the world view beginning in the 12th century. Meanwhile, cartography developed along more practical and realistic lines in Arabic lands, including the Mediterranean region. All maps were, of course, drawn and illuminated by hand, which made the distribution of maps extremely limited.

Hereford Mappa Mundi, about 1300, Hereford Cathedral, England. A classic "T-O" map with Jerusalem at center and east toward the top. Taken from Whitfield (1994, p. 21).


Al-Idrisi's map of the world, 1456. Al-Idrisi was a muslim scholar in the court of King Roger II of Sicily. He completed a map of the known world in the 12th century. Drawn with south at the top, this later example has been inverted for easier viewing. Taken from Whitfield (1994, p. 29).

Northern regions map from S. Munster's Cosmographia (1588). North Atlantic region is essentially a Viking view dating from the 12-14th centuries. One of the last wood-engraved maps, done in the style of copper-plate engraving. Published posthumously by H. Petri (son in law) in Basle, Switzerland.


Renaissance Maps The invention of printing made maps much more widely available beginning in the 15th century. Maps were at first printed using carved wooden blocks. Printing with engraved copper plates appeared in the 16th century and continued to be the standard until photographic techniques were developed. Major advances in cartography took place during the Age of Exploration in the 15th and 16th centuries. Map makers responded with navigation charts, which depicted coast lines, islands, rivers, harbors, and features of sailing interest. Compass lines and other navigation aids were included. Such maps were held in great value for economic, military, and diplomatic purposes, and so were often treated as national or commercial secrets--classified or proprietary maps.

Genoese nautical chart of the world, 1457. Taken from Whitfield (1994, p. 40-41). The first whole world maps began to appear in the early 16th century, following voyages by Columbus and others to the New World. Gerardus Mercator of Flanders (Belgium) was the leading cartographer of the mid-16th century. He developed a cylindrical projection that is still widely used for navigation charts and global maps. He published a map of the world in 1569 based on this projection. Many other map projections were soon developed.

Waldseemüller's world map, 1507, the first map to incorporate New World discoveries. This map is based on the Ptolemaic projection, but does not show the entire globe. Taken from Whitfield (1994, p. 48-49).


Detail of Ptolemy and "old world" from Waldseemüller's world map, 1507. This detail depicts the Old World in the Ptolemaic projection. Taken from Whitfield (1994, p. 11).

Detail of Americi Vespucci and "new world" from Waldseemüller's world map, 1507. This detail depicts the New World in the Ptolemaic projection. Taken from Whitfield (1994, p. 37).

World map of Rosselli, 1508, the first map to show the entire globe. A mythical southern continent is shown, and ocean areas are much too small. Nonetheless, it is a true world map. Taken from Whitfield (1994, p. 50-51).


Heart-shaped world map of Apian, 1530. A fully expanded Ptolemaic projection of the world results in this heart-shaped map. Popular during the Renaissance, this kind of map is a novelty today. Taken from Whitfield (1994, p. 57).

World map in Mercator projection by van Keulen, about 1720. The ultimate map for navigation of the world, as first devised by Mercator (1569). On this projection, all straight lines are true bearings. This results in great size distortion toward the poles, which cannot be shown. Taken from Whitfield (1994, p. 108-109).


Modern Maps Maps became increasingly accurate and factual during the 17th, 18th and 19th centuries with the application of scientific methods. Many countries undertook national mapping programs. Nonetheless, much of the world was poorly known until the widespread use of aerial photography following World War II. Modern cartography is based on a combination of ground observations and remote sensing.

Map of the Danish Kingdom, 1629, by Janssonius. A high level of geographic accuracy is demonstrated along with marginal illustrations that enhance the map. Reproduction of original map from the Geodetical Institute of Denmark. Hondius' world map in two hemispheres, 1630, the quintessential Renaissance map. Taken from Whitfield (1994, p. 75).


Henry Beck’s Map of London Underground: The London underground rail system was getting complex in the 1930’s and the map designers were having a hard time fitting all the stations into the standard issue card folder.

Un-intimidated by cartographic convention, an out-of-work engineering draughtsman called Henry Beck plotted the underground as if he was sketching an electrical circuit board. He used only vertical, horizontal, or 45 degrees angled colored lines; located the stations according to available space; and evened out the distances between stations. The resulting “map” although geographically inaccurate, provided a coherent overview of a complex system.


The map was an instant success and for Londoners it became the organizing image of their city. “The map organized London, rather than London organizing the map”, remarks Tufte. (There was an interesting and unwitting fallout from Beck’s map. The map telescoped scale, and brought the suburbs closer to central London. Suddenly, Watford was no further from Paddington than Liverpool Street. The map lubricated the exodus of London's inner-city dwellers as nearly half a million people were enticed out to the suburbs, where they found themselves captive customers of their local tube station).

Beck’s map is by far the most successful infographic as it continues to accommodate the ever expanding rail network and inspires design of countless other route maps world-wide. This success is due to 2 design strategies that the map employs. First, the map places importance on function over precise geography. A commuter is interested in how to go from one station to another. All he needs to know are: which line to take, where to change lines, and what are the preceding stations. The map fulfills this need by simple lines (which ensure an uncluttered layout), color (which differentiates the lines), clear typography (which makes text easy to read), and symbols (which differentiate stations from interchanges).

Second, the map capitalizes on the fact that the system operates underground and therefore the commuters need not be burdened with the confusing topography above ground. The only surface feature to survive was the River Thames. The map makes complex information simple by eliminating all extraneous details.


The vision of George Rorick (http://www.poynterextra.org/George/index.htm). At a time when graphics in Newspapers were considered time consuming and distracting, George Rorick5, pioneered the use of graphics as an important component of news communication. He envisioned USA Today as a visual Newspaper – “Visuals that help people understand the news. And color, of all things!” However, he is best known for the weather graphics, which revolutionized the way we read weather information and is probably the most imitated news infographic (fig.23). Using a combination of color, maps, tables, symbols, and annotation, Rorick transformed a hitherto dull and often hard to understand information into something very interesting and accessible. Rorick’s greater legacy though was his efforts in gaining a widespread acceptance for visual journalism in a profession dominated by text, establishing a business case for infographics, and formalizing a production process within the newsroom setup that churn out consistent quality infographics on a continuous basis under tight deadlines.


Geographic information systems (GIS) emerged in the 1970-80s period. GIS represents a major shift in the cartography paradigm. In traditional (paper) cartography, the map was both the database and the display of geographic information. For GIS, the database, analysis, and display are physically and conceptually separate aspects of handling geographic data. Geographic information systems comprise computer hardware, software, digital data, people, organizations, and institutions for collecting, storing, analyzing, and displaying georeferenced information about the Earth (Nyerges 1993).


What is a Map? Are maps realistic representations of the actual world? No--never! Field measurements are subject to errors of accuracy and precision. Aerial photographs and satellite images portray only certain portions of the light spectrum, as filtered through the atmosphere and detection instruments. No map can depict all physical, biological, and cultural features for even the smallest area. A map can display only a few selected features, which are portrayed usually in highly symbolic styles according to some kind of classification scheme. In these ways, all maps are estimations, generalizations, and interpretations of true geographic conditions.

What is a Map Projection? A map projection is a way to represent the curved surface of the Earth on the flat surface of a map. A good globe can provide the most accurate representation of the Earth. However, a globe isn't practical for many of the functions for which we require maps. Map projections allow us to represent some or all of the Earth's surface, at a wide variety of scales, on a flat, easily transportable surface, such as a sheet of paper. Map projections also apply to digital map data, which can be presented on a computer screen. There are hundreds of different map projections. The process of transferring information from the Earth to a map causes every projection to distort at least one aspect of the real world – either shape, area, distance, or direction. Each map projection has advantages and disadvantages; the appropriate projection for a map depends on the scale of the map, and on the purposes for which it will be used. For example, a projection may have unacceptable distortions if used to map the entire country, but may be an excellent choice for a large-scale (detailed) map of a county. The properties of a map projection may also influence some of the design features of the map. Some projections are good for small areas, some are good for mapping areas with a large east-west extent, and some are better for mapping areas with a large north-south extent. Some projections have special properties. For example, a Mercator projection has straight rhumb lines and is therefore excellent for navigation, because compass courses are easy to determine.


Geodesy or geodetics, is the scientific discipline that deals with the measurement and representation of the earth, its gravitational field, and other geodynamic phenomena, such as crustal motion, oceanic tides, and polar motion. Classes of Map Projections and Their Use There are several ways to classify the wide variety of map projections. One of the most common classifications is by distortion characteristics: which properties of the Earth does the projection maintain? Which does it distort? Classification based on distortion characteristics A projection that maintains accurate relative sizes is called an equal area, or equivalent projection. These projections are used for maps that show distributions or other phenomena where showing area accurately is important. Examples are the Lambert Azimuthal Equal-Area projection and the Albers Equal-Area Conic projection. The National Atlas of the United States uses a Lambert Azimuthal Equal-Area projection to display information in the online Map Maker. In addition to its equal-area properties, this projection also shows true directions from the center point of the map. This means that the projection works well for mapping areas that extend equally from the center point, such as North America. Mercator projection A projection that maintains angular relationships and accurate shapes over small areas is called a conformal projection. These projections are used where angular relationships are important, such as for navigational or meteorological charts. Examples are the Mercator projection and the Lambert Conformal Conic projection. The U.S. Geological Survey uses a conformal projection for many of its topographic maps. A projection that maintains accurate distances from the center of the projection or along given lines is called an equidistant projection. These projections are used for radio and seismic mapping, and for navigation. Examples are the Equidistant Conic projection and the Equirectangular projection. The Azimuthal Equidistant projection is the projection used for the emblem of the United Nations. A projection that maintains accurate directions (and therefore angular relationships) from a given central point is called an azimuthal or zenithal projection. These projections are used for aeronautical charts and other maps where directional relationships are important. Examples are the Gnomonic projection and the Lambert Azimuthal Equal-Area projection. A map projection may combine several of these characteristics, or may be a compromise that distorts all the properties of shape, area, distance, and direction, within some acceptable limit. Examples of compromise projections are the Winkel Tripel projection and the Robinson projection, often used for world maps.


Classification based on developable surface Map projections can also be classified based on the shape of the developable surface to which the Earth's surface is projected. A developable surface is a simple geometric form capable of being flattened without stretching, such as a cylinder, cone, or plane. Cylindrical projection For example, a cylindrical projection projects information from the spherical Earth to a cylinder. The cylinder may be either tangent to the Earth along a selected line, or may be secant (intersect the Earth) along two lines. Imagine that once the Earth's surface is projected, the cylinder is unwrapped to form a flat surface. The lines where the cylinder is tangent or secant are the places with the least distortion. A Mercator projection is created using a cylinder tangent at the equator. A Transverse Mercator projection is created using a cylinder that is tangent at a selected meridian. An Oblique Mercator projection is created using a cylinder that is tangent along a great circle other than the equator or a meridian. A conic projection projects information from the spherical Earth to a cone that is either tangent to the Earth at a single parallel, or that is secant at two standard parallels. Once the projection is complete, the cone is unwrapped to form a flat surface. The lines where the cone is tangent or secant are the places with the least distortion. A polyconic projection uses a series of cones to reduce distortion. A planar projection projects information to a plane. The plane may be either tangent or secant.


Commonly Used Map Projection Terms Azimuth—The angle, measured in degrees, between a base line radiating from a center point and another line radiating from the same point. Normally, the base line points North, and degrees are measured clockwise from the base line. Azimuthal—A map projection in which the direction from a given central point to any other point is shown correctly. Also called a zenithal projection. Aspect—The placement of a projection system relative to the Earth's axis. A polar aspect is tangent at the pole, an equatorial aspect is tangent at the Equator, and an oblique aspect is tangent anywhere else. (The word "aspect" has replaced the word "case" in the modern cartographic literature.) Cartesian coordinate system —A coordinate system in which a point's location is described by its distances from a set of perpendicular lines that intersect at an origin, either two lines in a plane or three in space. Conformal—A map projection in which the angles at each point are preserved. This means that the shapes of small areas are maintained accurately. The size of most areas, however, is distorted. Conic—A map projection where the Earth's surface is projected onto a tangent or secant cone, which is then cut from apex to base and laid flat.

Cylindrical—A map projection where the Earth's surface is projected onto a tangent or secant cylinder, which is then cut lengthwise and laid flat. Datum—A reference for position on the surface of the Earth. In surveying, a datum is a reference system for computing or correlating the results of surveys. There are two principal types of datums: vertical and horizontal. A vertical datum is a level surface to which heights are referred. In the United States, the generally adopted vertical datum for leveling operations is the National Geodetic Vertical Datum of 1929. The horizontal datum is used as a reference for position. The North American Datum of 1983 is based on the Geodetic Reference System 1980 (GRS80) spheroid; it is an Earth-centered datum having no initial point or initial direction. This is the horizontal datum used for National Atlas map layers. Developable surface—A developable surface is a simple geometric form capable of being flattened without stretching. Map projections can be grouped by the developable surface they use: cylinder, cone, or plane.


Ellipsoid—A mathematical figure that approximates the shape of the Earth in form and size, and which is used as a reference surface for geodetic surveys. Used interchangeably with Spheriod. Equal-area—A map projection where every part, as well as the whole, has the same area as the corresponding part on the Earth, at the same reduced scale. Equator—The line which encircles the Earth at an equal distance from the North and South Poles. Equidistant—A map projection that shows true distances from the center of the projection or along a special set of lines. For example, an Azimuthal Equidistant map centered at Washington, DC, shows the correct distance between Washington, DC, and any other point on the projection. It shows the correct distance between Washington, DC, and San Diego and between Washington, DC, and Seattle, but it does not show the correct distance between San Diego and Seattle. Graticule—A network of lines representing a selection of the Earth's parallels and meridians. Great circle—A circle formed on the surface of a sphere by a plane that passes through the center of the sphere. The Equator, each meridian, and each other full circumference of the Earth forms a great circle. The arc of a great circle shows the shortest distance between points on the surface of the Earth. Grid—Two sets of parallel lines intersecting at right angles, forming a rectangular Cartesian coordinate system superimposed on a map projection. Sometimes the term "grid" is used loosely to mean the projection system itself rather than the rectangular system superimposed on the projection. Latitude—Angular distance, in degrees, minutes, and seconds measured from the center of the Earth, of a point north or south of the Equator. Latitude may also be measured in decimal degrees. Longitude—Angular distance, in degrees, minutes, and seconds measured from the center of the Earth, of a point east or west of the Prime Meridian. Longitude may also be measured in decimal degrees. Meridian—A great circle on the surface of the Earth, passing through the geographical poles and some third point on the Earth's surface. All points on a given meridian have the same longitude. Parallel—A circle or approximation of a circle on the surface of the Earth, parallel to the Equator and connecting points of equal latitude. Planar—A map projection resulting from the conceptual projection of the Earth onto a tangent or secant plane. Usually, a planar projection is the same as an azimuthal projection.


Prime Meridian—The meridian of longitude 0 degrees, used as the origin for the measurement of longitude. The meridian of Greenwich, England, is the internationally accepted prime meridian in most cases. Projection parameters—A series of values that define a particular projection, and that tell how the projection is related to the Earth. Projection parameters may indicate the point of tangency, or the lines where a secant surface intersects the Earth. They also define the spheriod used to create the projection, and any other information necessary to identify the projection. Rhumb line—A rhumb line is a line on the surface of the Earth cutting all meridians at the same angle. A rhumb line shows true direction. Parallels and meridians, which also maintain constant true directions, may be considered special cases of the rhumb line. A rhumb line is a straight line on a Mercator projection. A straight rhumb line does not show the shortest distance between points unless the points are on the Equator or on the same meridian. A navigator can proceed between any two points along a rhumb line by maintaining a constant bearing, or compass direction. Scale—The relationship between a distance on a map, chart, or photograph, and the corresponding distance on the Earth. Scale is usually given as a fraction or ratio: 1:2,000,000, or 1/2,000,000. Secant—Cutting the sphere or spheroid along a line or lines. A secant cone or cylinder intersects the sphere or spheroid along two separate lines; these lines are parallels of latitude if the axes of the geometric figures coincide. A secant plane intersects the sphere or spheroid along a line that is a parallel of latitude if the plane is at right angles to the axis. Spherical – Approximating the shape of a sphere. Spheroid—A mathematical figure that approximates the shape of the Earth in form and size, and which is used as a reference surface for geodetic surveys. Used interchangeably with Ellipsoid. Tangent—Touching at a single point or along a single line. A tangent cone or cylinder touches the sphere or spheroid along a single line. This line is a parallel of latitude if the axes of the geometric figures coincide. Zenithal—A map projection in which the direction from a given central point to any other point is shown correctly. Also called an azimuthal projection.

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What is a Map? - schroeppel-design.de · Early Maps Cartography is the art and science of making maps. The oldest known maps are preserved on Babylonian clay tablets from about 2300