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Nature Gallery (Geography)
How to read a map
What Is a Map?
A map is a representation of a geographic area, usually a portion of the Earth's surface. It may be shown in many different ways, from a traditional map printed on paper to a digital map built pixel by pixel on the screen of a computer. Maps can show almost anything, from the electricity supply grid of your area to the terrain of the Himalayas or the depths of the ocean floor. A map can be practical, directing travelers from one point to another through confusing landscape, or explaining the world by attaching specific types of information to geography. Maps can also entertain and invite exploration. 

For example, a colorful map of the Marquesas Islands with exotic-sounding ports such as Hakapehi on Nuku Hiva might sound appealing to some. Similarly, a detailed map of the many features of Athens or Bangkok might entice others. A map can even be created for the surface of Mars, based on data transmitted to Earth from computer-controlled spacecraft, showing places that most people will never visit.

Maps can be drawn in many different styles, each showing different faces of the same subject and allowing us to visualize the world in a convenient, informative, or stimulating way. The few simple skills and facts described here will help you to use maps effectively. In addition, be aware of these important facts:

  • No map is perfect. People make maps from data they collect with certain tools. Even computer-generated maps depend on programmes and machines designed by people. People make mistakes and machines are never totally accurate, no device can record every detail of a landscape. Maps, therefore, can contain errors and inaccuracies. Data or cartographic errors could result in a certain village not being exactly where the map shows or a mountain peak not being exactly as high as it appears on the map.

Cartographers who use traditional tools, such as recording ground data by hand or using high-altitude photography, are limited by how many objects they can record and how small these objects can be. Very small features may not be accurately placed or may not appear at all. Modern tools such as high-resolution satellite photography can record details to a resolution of several meters. Most surface objects of practical importance can be recorded with such imagery and translated into highly accurate maps or photographs, but they are still subject to interpretation and data error. Cartographers sometimes purposely limit the details they present in a map in order to make the map less confusing.

  • Maps also become outdated, no longer showing the world accurately. This is because the world is constantly changing both physically and culturally. Modern technology has provided a partial solution-computers have made it possible to renew maps easily without redrawing them. However, appropriate information reflecting changes in the world must still be collected periodically and used to revise the maps' databases.
  • Maps are biased. Maps generally do not show every single feature of a chosen geographic area-every tree, house, or road-so the cartographer must decide the projection and scale of the map and the amount of detail to present. The purpose of the map and the cultural background of the cartographer often dictate this process, which is called generalization. Information on the map and how it may be distorted can influence what people think about the world and what they do.

Map Types

The first question to ask about a map is what its theme is. This is the particular aspect of the world that the map attempts to show, such as roads, borders, vegetation, or statistical data. Maps can be divided by theme into three categories. The first, general maps, are those that contain many themes and give a broad picture. General maps are often practical, showing the world in a way that allows people to get from one point to another without getting lost, or shows the overall layout of an unfamiliar place without having to go there. 

An example of a general map is a road map of a country also showing major cities, mountains, rivers, landmarks, etc. The second category is thematic maps, which contain either one or several themes and show in-depth information. Thematic maps can show almost any kind of information that varies from place to place, such as a country's population or income level by state, province, or county, with each division colored differently to indicate the relative level of population or income. The third category of map is charts, which are accurate maps of routes of travel used for ocean and air navigation. They must be updated frequently so that captains and pilots know of current dangers along their route.

Maps are made in many different forms. The first maps made by people were probably lines drawn in sand or small pebbles and sticks arranged on the ground. Modern maps are published for the long-term use of many people. Printed maps are the simplest forms. They show the world as flat-that is, in two dimensions. On a printed map, relief-mountains, valleys, and other terrain-is shown with special symbols to make up for the lack of depth, which is the third dimension. Relief maps are rigid flat maps with actual bumps and depressions added to indicate elevated landforms and low areas. They are usually made of clay or moulded plastic, and the relief is usually exaggerated to give a greater impression of height.

In between the effects created by flat maps and relief maps is the visual experience created by stereograms. These give the effect of viewing actual relief because they stimulate what our eyes see. They use two maps or aerial photographs of the same area but taken from slightly different angles. By looking through a stereoscope, which has two lenses a small distance apart, the eyes synthesize the information to provide a 3-dimensional view. Globes are another way of mapping. They are spherical models of planets such as the Earth or the Moon. They give a more realistic impression of features on a curved surface.

Computer maps are the most versatile. A mapping program can dynamically show many different views of the same subject. It can also allow changes in scale, and incorporate animation, pictures, sound, and Internet links to sources of supplementary information. Computer-generated maps can be updated to present more themes and geographic detail. This is because new information can be entered into their databases over time. Having a powerful digital map is like having dozens of printed thematic maps overlaid on a particular area, each electronically connected to an immense library of information on the main theme and on many related ones.

The way that people use a map depends on the type of map they have and what sort of information they want from it. In the case of simple maps, only one or two types of information may be available and few or no map skills are required to use it. For example, a sketch of a neighbourhood may only show what relationship a particular house has to the street corner or whether it is farther from there to the market or to the school. Even those who cannot read the local language can use such maps. Complex maps, however, can indicate actual distance, the exact location of land features, elevation, vegetation, political divisions, and many other aspects of the world. To interpret such a complex map, some basic map skills are required.

Map Elements
Most maps, including the majority of maps of the Earth, share a number of basic features. They assume a certain projection and scale, express location in terms of coordinates, and have a legend. mapprojetion1.gif (149223 bytes)
Projection
The surface of the Earth is curved and maps are flat, whether they are printed maps or computer screen pictures. This means that all maps except for globes and pictures of globes are distortions of how the Earth really looks. For small areas, the distortion is insignificant because small areas on the globe look like a flat surface. For large areas or for purposes demanding high accuracy, however, such distortion can be very important. We can see how map distortions occur if we look at an orange peel. When the curved outer surface of an orange is removed and laid flat, the peel spreads out in separate pieces. Cartographers face the same problem when mapping the surface of the Earth. They have to remove the pieces of geography in a certain way and stretch or stitch the pieces together again in order to make a continuous flat map.

The way the geography of the Earth is taken from the globe and reassembled on a flat surface is called the map's projection. Another way of thinking of projection is that every point on the globe can be projected by a straight line onto a transparent form wrapped around the globe. The shape of the form and how the points are spread onto it determine the type of projection. Some common forms are cylinders, cones, ellipses, and flat planes, giving rise to cylindrical, conic, elliptical, and orthographic projections. 

There are many types of projection. Each distorts the spherical surface of the Earth in a different way, and each has its practical advantages and disadvantages.

It is impossible to take information from a curved surface and fit it onto a flat surface with complete accuracy. The only way to keep accuracy is to map on a spherical surface-a globe. Any flat map projection will have to compromise on one of the following: area, distance, or direction. Different projections take different views. 

One often-used projection is called the Mercator projection, named after the Flemish geographer Gerardius Mercator. This is a variation of a cylindrical map. It maintains direction and distance, but area in high latitudes-towards the poles-is compromised. For example, India has a larger area than Greenland, yet on a mercator projection Greenland looks many times larger. 

The Peter's projection, by contrast, represents area as accurately as possible. However, this means that the shape of the land masses becomes distorted.

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Scale

The size of a map in relation to the Earth is its scale, which is usually stated as a fraction or ratio. The numerator, at the top of the fraction, is one unit on the map and the denominator, at the bottom of the fraction, is the number of the same units that are represented in the real world. For example, a scale of 1/10,000 means that one centimetre on the map is equivalent to 10,000 centimetres on the ground. As a ratio, this scale would be shown as 1:10,000. The larger the denominator and the smaller the fraction, the more of the Earth is represented on a single map. Therefore, small-scale maps show a large piece of the Earth, and large-scale maps show a relatively small piece.

Computer maps may have a varying scale that changes according to the "zoom" level of the view. The more zoomed in, or closer you are to the Earth, the larger the depicted scale.

Coordinate Position

The surface of the globe is divided into a spherical grid for the convenience of finding certain points. The grid consists of imaginary lines called latitude and longitude. Latitude is a series of concentric circles running parallel to the equator and extending to both poles. Longitude is a series of meridians, or longitudinal lines drawn between the poles at regular intervals that pass perpendicularly through the equator. Where a particular latitude crosses a particular longitude, a pair of numbers, or coordinates, can be assigned. Every point on the Earth has a set of coordinates that indicate its position relative to every other point.

Latitude is measured from zero at the equator to 90 degrees north and south at the poles. Longitude is measured from zero to 180 degrees west and east. The reference lines for counting are the equator, for latitude, and a line drawn through Greenwich in England, the prime meridian, for longitude. These are the zero lines. A degree of latitude is equivalent to about 112 kilometers (70 miles). Longitudinal lines converge toward the poles, meaning that degrees of longitude vary according to the position on the Earth. At the equator, one degree of longitude is the same length as one degree of latitude, and at the north and south poles, the distance between degrees of longitude is zero.

Degrees are divided into 60 minutes, and each minute is divided into 60 seconds. For example, the Eiffel Tower in Paris has the following coordinates: latitude 48 51' 32" north and 2 17' 35" east. Sometimes, coordinates are expressed in decimal minutes instead of minutes and seconds, so the coordinates of the Eiffel Tower can also be written as 48 51.5333 north latitude and 2 17.5833 east longitude.

Most official maps indicate latitude and longitude, so viewers know exactly what part of the Earth the map represents.

Some maps have other special-purpose coordinate systems, such as the State Plane Coordinate System used on maps in the United States or the Universal Trans-Mercator (UTM) system used on many military maps.

Legend

Maps use sets of symbols to indicate the placement of real objects. The legend is a block of text or a window in which the symbols used on the map are explained. Legend symbols can include icons to represent buildings, different colors to indicate elevation, different types of lines to indicate borders or roads of varying size, and dots and circles to show the relative population of towns and cities. If the details of a map look unfamiliar, it is helpful to study the legend before proceeding further.

Direction: Which Way Is Up?

Most maps give a reference point to indicate how a direction on the map corresponds to a direction in the real world. This is crucial when using the map to travel between points. A good map indicates a cardinal direction for such orientation, usually by an arrow pointing north. Maps from past centuries used various cardinal directions. Some older European maps placed East at the top, pointing to the area then known as the Orient, leading to the term "orientation". Old Muslim maps put South facing upwards. 

Modern maps usually adopt the convention that the top of the map corresponds to North, the bottom to South, the left edge to West, and the right edge to East. Direction can also be determined from coordinates, if they are shown. Using the maps in Encarta World Atlas is like holding a globe in your hands-any view of the Earth can be examined. All views are oriented with North as up except when the map is centered on the North Pole or South Pole.

The poles representing the rotational axis of the Earth do not correspond to the magnetic poles-the direction in which a compass points. This is because the magnetic poles constantly change position or wander. The north-pointing arrow on many accurate maps is divided into two parts, one indicating polar and one indicating magnetic north. The angular difference between these is known as the map's magnetic declination. 

For example, according to a 1987 map of Moscow, the compass points to magnetic north at 7 46' to the right of true polar north, so the magnetic

The Ups and Downs of Maps: Elevation

Topography adds a third dimension to the flat-map picture of the world. Cartographers use different techniques to indicate topography, which means the hills and valleys of the surface of the Earth. Early maps used bars, or lines of overlapping triangles to show hills or mountain ranges.  mapprojection5.gif (163988 bytes)
A few ancient maps, including a Buddhist map from 14th-century Japan, show mountains as artistic, three-dimensional figures. Symbols such as hatched or spoked symbols were also used on some European maps. 

Modern maps show mountains in shaded relief, called hill shading. Traditional topographic maps use concentric lines, called contour or hypsographic lines, to indicate elevation. Each line is assigned a height above sea level. These lines link all places of the same elevation and are usually marked at a regular interval. Having a lot of lines together indicates a rapid change in elevation; longer spaces between indicate flatter land. Corresponding lines indicating ocean depth are called hydrographic lines.

Instead of concentric lines, color maps often use a standardized color scale to indicate elevation: sea level is blue; low elevations are shades of green; higher elevations range from tan to brown; and the highest peaks are shown in white, suggesting snow. Deeper shades of blue correspond to deeper parts of lakes or oceans.

Learning to read maps is easy and intuitive. A person can use the map skills discussed in this article to solve navigation problems, plan future activities, or discover more about the world.