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Map

For alternative meanings see Map (disambiguation)

Table of contents

1 Introduction 2 Electronic maps 3 Other uses 4 Maps on Wikipedia 5 Links and references 5.1 References 5.2 See also 5.3 External links

Introduction

Many maps have a scale, determining how large objects on the map are in relation to their actual size. A larger scale shows more detail, thus requiring a larger map to show the same area. Some, though, are not drawn to scale - a famous example being the London Underground map.

If the map covers a large area of the surface of a globe, such as the Earth, it also has a projection, a way of translating the three-dimensional real surface of the geoid to a two-dimensional picture. One commonly used for navigation is the Mercator Projection; other popular projections are polar and a variety of equal-area projections.

The features shown on a map vary according to its purpose. For example, a road map may or may not show railroads, and if it does, it may show them less clearly than highways.

Maps can be political or geographical. The most important purpose of the political map is to show territorial borders; the purpose of the geographical is to show features of physical geography such as mountains, soil type or land use. Geological maps show not only the physical surface, but characteristics of the underlying rock, fault lines, and subsurface structures.

Many surveying projects have been carried out by the military. An example of this the British Ordnance Survey (which now is a civilian government agency).

Because maps are abstract representations of the world they are not neutral documents and must be carefully interpreted. It is, of course, this abstraction that makes them useful. Lewis Carroll made this point humorously in Sylvie and Bruno with his mention of a fictional map that had "the scale of a mile to the mile." A character notes some practical difficulties with this map and states that "we now use the country itself, as its own map, and I assure you it does nearly as well."

Electronic maps

For maps on a computer display, e.g. from the web or locally stored on CD-ROM or harddisk, zooming in means enlarging the scale, either by showing a smaller area in the same viewing window or by showing the same area in a larger viewing window, and one of the following:

• replace the map by a more detailed one
• enlarge the same map without enlarging the pixels, hence show more detail
• enlarge the same map with the pixels enlarged (replaced by rectangles of pixels); no additional detail is shown, but, depending on the quality of one's vision, possibly more detail can be seen; if a computer display does not show adjacent pixels really separate, but overlapping instead (this does not apply for an LCD display, but may apply for a CRT), then replacing a pixel by a rectangle of pixels does show more detail.

For a single raster graphics image the second applies until the pixels in the image file correspond to the pixels of the display; on further zooming in, the third applies.

For a PDF-file typically the second applies. The increase in detail is, of course, limited to the information contained in the file: enlarging a curve it may eventually become a series of straight line segments, or other standard geometric figures such as arcs of circles.

A variation of the third possibility is that interpolation is performed.

Text is not necessarily enlarged when zooming in. Similarly, a road represented by a double line may or may not become wider when one zooms in. A variation of the first possibility above is that more text is displayed (such as more town names), but that for the rest of the image the second applies.

See also Webpage#Graphics, Portable Document Format#Layers.

Other uses

• Road map is also used metaphorically for a plan, for example "Road map for peace".
• In computer games, a map is synonymous to a level. In the context of modifications, especially for first person shooters, the word map likewise refers to the full distribution-ready set of data for a map - for example, the map "de_dust" in Counter-Strike includes the brushes, textures, bomb sites, spawn points, and backgrounds.
• Songlines as maps in Australian Aborigine culture.

Links and references

References

• Atlas (cartography)
• Topographic map
• Geologic map

• Multimap world atlas: on UK, US, Canada, Australia and Western Europe more detailed than the rest of the world
• [1] - Microsoft/Encarta/Expedia world atlas, for North America and Europe to street level.
• MapQuest: on US, Canada and Western Europe more detailed than the rest of the world
• Yahoo Maps: on US, Canada, Germany, France, Spain, Italy
• Yahoo Germany: on France, UK, Germany, Italy, Spain, Portugal, Austria, Switzerland, Benelux
• Map South Pacific: on Polynesia, Melanesia, Micronesia
• [1] - ESRI atlas of the US
• National Atlas of the United States
• Small country maps, conveniently linked from continent maps
• UT scanned collection: by the University of Texas at Austin
• Example of legend (Cito-Plan city maps)
• http://www.geocities.com/marcoschmidt.geo/geo-data.html
• USGS National Map

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