CONVENTIONAL AND MODERN TOOLS OF GEOGRAPHY (перевод)
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CONVENTIONAL AND MODERN TOOLS OF GEOGRAPHY
Despite their variety, all maps have similar components, or parts. These include a title; a legend or key; a direction indicator; and a scale.
The title of a map. It identifies what the map is about and what parts of the earth it shows. The title of some maps includes a date. Dates are useful on maps showing features that change over time. A map with the title “Distribution of Population in France: 1920”, for example, should not be used when looking for figures on the present population of France.
A legend. A legend or key explains the meaning of colors and symbols used on a map. A map with areas shown in green, red, and blue might be misunderstood unless the user knows what the green, red, and blue represent. The legend also explains the meaning of symbols used on a map, such as stars for capital cities.
A direction indicator. Every map should have a direction indicator. One such indicator is an arrow that points north. A different way to find directions on a map is to study the parallels and meridians. East and west directions follow parallels, or lines of latitude. North and south directions follow meridians, or lines of longitude. Parallels and meridians cross each other to form an imaginary grid over the earth. Because each degree can be broken into 60 minutes (ʹ) and each minute can be broken into 60 seconds (ʺ), this grid can be used to fix the precise location of any point on the earth’s surface.
The most important longitude is called the Greenwich Meridian, because it passes through a place called Greenwich in London where there is a famous observatory. The longitude of the Greenwich Meridian is 0 degrees. At Greenwich local time is called Greenwich Mean Time (GMT). All places on the same meridian have the same local time. When it is noon at a given meridian, it is after noon or post meridiem (p.m.) at places which lie to the east of it. This is because the earth rotates from west to east. At the same time the sun will be before noon or ante meridiem (a.m.) at places lying to the west.
Map scales and projections. A map scale provides statistical information used to measure distances on a map. While maps have similar components, they do not always show areas of the world in exactly the same way. The size and shape of North America, for example, may look somewhat different on two different maps. The differences occur because the two maps use different map projections, or methods by which the features of the earth’s curved surface are transferred onto a flat map.
No matter which projection is used, every map has some distortions
No matter which projection is used, every map has some distortions that are inevitable in the process of illustrating the earth’s spherical surface on a flat map. Certain distortions, however, are worse on some projections than on others. Mapmakers choose which projection to use depending on what undistorted features, or map properties, are most important to be illustrated. The four most useful map properties are correct shape, correct size, correct distance, and correct direction. No world map can have all four map properties. Maps of smaller areas, however, may have less distortion than maps of larger areas.
Rapid developments in technology have made several new tools available. These tools already have provided a wide range of valuable information about the earth’s surface. Remote sensing, the gathering and recording of information through aerial photographs and satellite images, ranks among the most important of the new methods.
Aerial photographs. Geographers use aerial photographs — pictures taken from above the earth — to study relationships involving people and places that are not easily seen from ground level. Aerial photographs of traffic patterns, for example, can be used to help plan new highways. Military planners can see troop movements and rocket launch sites. Foresters can spot diseased or insect-infested trees in rugged terrain that would be hard to reach on foot. Aerial photographs even show features of the ocean floor.
Because aerial photographs provide such accurate and detailed information, cartographers rely on them as a source of information when making maps. Most aerial photographs used to make maps are taken by cameras in high-altitude airplanes and are developed in strips of overlapping pictures. An instrument called a stereoscope converts a pair of overlapping aerial photographs into a three-dimensional view of the area.
Elevations appear somewhat distorted on aerial photographs because the camera taking the pictures is closer to the tops of the mountains than to the valleys. As a result, mountains appear larger than the more distant valleys. This distortion is corrected by using a viewing instrument called a stereoplotter, which gives a more accurate three-dimensional view of the earth.
Satellite images. Many of the satellites circling (revolving around) the earth have special sensors called multispectral scanners. These scanners record observations electronically and send them to ground stations. Computers then translate the data into electronic images, making false- color pictures. Even though the pictures are taken from far in space, they are so detailed that they can show houses or even sailboats on a lake.
An extraordinary group of earth satellites known as Landsats take many of the satellite images. These satellites circle the earth 14 times every 24 hours, silently scanning, collecting, and sending back a greater view of the world than any eye could ever see.
In addition to globes, maps, and remotely sensed images, geographers use tables, charts, graphs, and diagrams to help them in their work. Geographers also use computers to solve geographic problems as well as to make maps and graphics.
1. What components do maps have?
2. What is the unit for measuring latitude and longitude?
3. Why is the global grid significant?
4. What are the four most useful map properties?
5. Why are aerial photographs and satellite images especially useful to geographers?
6. Why do elevations appear somewhat distorted on aerial photographs?
7. How do computers help geographers?
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