Eratosthenes , around 250 BC, made major contributions to cartography. He measured the circumference of the Earth with great accuracy. He sketched, quite precisely, the route of the Nile to Khartoum, showing the two Ethiopian tributaries. He made another important contribution in using a grid to locate positions of places on the Earth. He was not the first to use such a grid for Dicaearchus, a follower of Aristotle , had devised one about 50 years earlier. Today we use latitude and longitude to determine such coordinates and Eratosthenes ' grid was of a similar nature. Note, of course, that the use of such positional grids are an early form of Cartesian geometry. Following Dicaearchus, Eratosthenes chose a line through Rhodes and the Pillars of Hercules (present day Gibraltar) to form one of the principal lines of his grid. This line is, to a quite high degree of accuracy, 36° north and Eratosthenes chose it since it divided the world as he knew it into two fairly equal parts and defined the longest east-west extent known. He chose a defining line for the north-south lines of his grid through Rhodes and drew seven parallel lines to each of his defining lines to form a rectangular grid.
Ptolemy's map of the world, about A.D. 150, republished in 1482. Notice the use of latitude and longitude lines
Hereford Mappa Mundi, about 1300, Hereford Cathedral, England. A classic &quot;T-O&quot; map with Jerusalem at center and east toward the top
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.
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.
Genoese nautical chart of the world, 1457.
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
Detail of Ptolemy and &quot;old world&quot; from Waldseemüller's world map, 1507. This detail depicts the Old World in the Ptolemaic projection.
Detail of Americi Vespucci and &quot;new world&quot; from Waldseemüller's world map, 1507. This detail depicts the New World in the Ptolemaic projection.
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 ma
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
Mercator made many new maps and globes, but his greatest contribution to cartography must be the Mercator projection . He realised that sailors incorrectly assumed that following a particular compass course would have them travel in a straight line. A ship sailing towards the same point of the compass would follow a curve called a loxodrome (also called a rhumb line or spherical helix), a curve which Pedro Nunes , a mathematician greatly admired by Mercator , had studied shortly before. A new globe which Gerardus Mercator produced in 1541 was the first to have rhumb lines shown on it. This work was an important stage in his developing the idea of the Mercator projection which he first used in 1569 for a wall map of the world on 18 separate sheets. The 'Mercator projection' has the property that lines of longitude, lines of latitude and rhomb lines all appear as straight lines on the map. In this projection the meridians are vertical and parallels having increased spacing in proportion to the secant of the latitude. Edward Wright published mathematical tables to be used in calculating Mercator's projection in 1599, see [ 20 ] for details.
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.
Hondius' world map in two hemispheres, 1630, the quintessential Renaissance map.
The fool's cap world map, about 1590. Ptolemaic projection on the face of a clown. Maker, date and place of publication are unknown. Maps are human representations of the world, as seen through the eyes of a fool in this example
A celestial map from the 17th century, by the Dutch cartographer Frederik de Wit.
Panoramic view of Phoenix, Arizona by C. J. Dyer in 1885. Compiled from drawings by topographic artists who walked the streets, these detailed bird's-eye perspectives are one expression of the optimism of urban life during the Victorian era.
The Robinson projection is a map projection popularly used since the 1960s to show the entire world at once. It was specifically created in an attempt to find the good compromise to the problem of readily showing the whole globe as a flat image.
Like many projections, the Robinson has advantages, and like all projections, it has disadvantages. The projection is neither equal-area nor conformal , abandoning both for a compromise. The creator felt this produced a better overall view than could be achieved by adhering to either. The meridians curve gently, avoiding extremes, but thereby stretch the poles into long lines instead of leaving them as points. Hence distortion close to the poles is severe but quickly declines to moderate levels moving away from them. The straight parallels imply severe angular distortion at the high latitudes toward the outer edges of the map, a fault inherent in any pseudocylindrical projection. However, at the time it was developed, the projection effectively met Rand McNally 's goal to produce appealing depictions of the entire world.
The Gall-Peters projection is one specialization of a configurable equal-area map projection known as the equal-area cylindric or cylindric equal-area projection. The Gall-Peters achieved considerable notoriety in the late 20th century as the centerpiece of a controversy surrounding the political implications of map design. Maps based on the projection continue to see use in some circles and are readily available, though few major map publishers produce them.
What is a map? <ul><li>A map is a representation, usually on a flat surface, of the features of an area of the earth or a portion of the heavens, showing them in their respective forms, sizes, and relationships according to some convention of representation. </li></ul>Now what does that mean?
Types of Maps <ul><li>There are three basic types of maps: </li></ul><ul><li>PHYSICAL </li></ul><ul><li>POLITICAL </li></ul><ul><li>and </li></ul><ul><li>THEMATIC. </li></ul>
Physical Maps <ul><li>Physical maps show the natural features of the Earth. </li></ul><ul><li>Physical maps do not contain man made features. </li></ul><ul><li>For example, a physical map would be a map of what you would see if you were looking down on Earth from space. </li></ul>
When you look at this map, what do you see? Notice you do not see country borders or city markings. These divisions are created by people. For example, there is no actual line dividing Texas from its bordering states. Although some astronauts (with the use of binoculars believe it or not) are able to see roads, large ocean tankers, and even the Great Pyramids from space, at very high altitudes, none of these are visible and all you are left with are natural land formations.
Political Maps Unlike physical maps, political maps show how humans have impacted the landscape. For example, city names, roads, country borders, etc. are all part of political maps. Political maps change frequently (physical maps change very, very slowly through geologic processes) and must be redrawn often. A political map of the world that is 50 years old is no longer accurate. Wars and ethnic conflict are two major causes political maps change.
Thematic Maps <ul><li>Thematic maps can represent a variety of information including things like climate, precipitation, vegetation, elevation, population, life expectancy, etc. </li></ul><ul><li>Thematic maps are generally used when you are looking at a single piece of information. </li></ul>
Parts of a map <ul><li>As we have learned, maps contain symbols that help you find places. They also have a map key that lists the symbols used on a map. It shows you what they mean. </li></ul>
Parts of a map <ul><li>A compass is a tool that shows direction on a map. It helps you to figure out whether you are traveling north, south, east, or west. </li></ul>
Parts of a map <ul><li>A map shows places smaller than they really are but it can show true distance using a map scale . A map scale is like a ruler. It is used to measure distance. </li></ul>
What is a globe? <ul><li>A globe is a model of the Earth. The green and brown parts represent the land and the blue represents the water . </li></ul>
What can we see on a globe? <ul><li>Like a map, a globe shows places on Earth. You can see the 7 continents and the 5 oceans. It shows every part of the Earth at one time! </li></ul>
What do we see on a globe? <ul><li>The globe also has a compass, but it is used in comparison to the poles. You may have heard of the North Pole. It is nothing but the northern half of the world. There is a North Pole and a South Pole. </li></ul>
What do we see on a globe? <ul><li>Globes also have a map key and map scale. A globe is just a map of the whole Earth. </li></ul>
What is the difference between a map and a globe? <ul><li>A map is a drawing that shows where places are. It is flat and drawn on a piece of paper. </li></ul><ul><li>and </li></ul><ul><li>A globe is a model of the Earth. Globes also show where places are. It is a sphere because it represents Earth and Earth is round. </li></ul>
What have we learned? <ul><li>Describe a map. </li></ul><ul><li>How is a map like a globe? </li></ul><ul><li>Describe a globe. </li></ul><ul><li>What is a map key? </li></ul><ul><li>What is the map scale used for? </li></ul><ul><li>What are borders? </li></ul><ul><li>What is the job of a compass? </li></ul>