|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
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:
|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
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.
|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.|
|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.
|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.
|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.
|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.|
| 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.