Jump to content

Map

Edit links
From Wikipedia, the free encyclopedia

This is an old revision of this page, as edited by Patrick (talk | contribs) at 21:42, 1 February 2005 (Reverted edits by Netoholic to last version by Bkobres). The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.

For alternative meanings see Map (disambiguation)
A map of the world by by Johannes Kepler

A map is a two-dimensional representation of a three-dimensional space. The science of making maps is called cartography.

Introduction

Mapmaking dates back at least to the Stone Age and appears to predate written language by several millennia. One of the oldest surviving maps is painted on a wall of the Catal Huyuk settlement in south-central Anatolia (now Turkey); it dates from about 6200 BC. [Harvey 2000, p. 142].

The making of maps is now often called cartography, or more simply map-making. In the last quarter of the 20th century, map-making has become inextricably entwined with computers. Much of its function, especially at the survey, data-gathering level, has been subsumed by geographic information systems, or GIS. Even when GIS is not involved, most cartographers now use a variety of computer graphics programs to generate new maps.

While we tend to think of maps today as products of a rationalistic, scientific world-view, maps also have a mythic quality. Pre-modern maps, and mapping traditions outside the Western tradition, often merge geography with non-scientific cosmography, showing the relationship of the viewer to the universe. Medeival "T-O" maps, for example, show Jerusalem at the centre of the world, and in some cases related the "body" of the Earth to the body of Christ. By contrast, navigational (or "Portolan") charts of the Mediterranean fromthe same period are remarkably accurate. Even today, maps can be powerful rhetorical tools beyond their purely practical value, and this has been the source of much fruitful map criticism over the last twenty years, notably in the works of J.B. Harley, Mark Monmonier and Denis Wood.

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. Maps which use some quality other than physical area to determine relative size are called cartograms.

Maps that depict the surface of the Earth also use a projection, a way of translating the three-dimensional real surface of the geoid to a two-dimensional picture, although informal directional maps and maps of very small areas need not hew cloesly to projections. Perhaps the best-known world-map projection is the Mercator Projection, originally invented to aid sea navigation.

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 of the world or of large areas tend to fall into two categories, political or physical. The most important purpose of the political map is to show territorial borders; the purpose of the physical is to show features of 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.

Road maps are perhaps the most widely used maps today, and form a subset of navigational maps, which also include aeronautical and nautical charts, railroad network maps, and hiking and bicycling maps. In tems of quantity, the largest number of drawn map sheets is probably made up by local surveys, carried out by municipalities, utilities, tax assesors, emergency services providers, and other local agencies for whom geographic information is their bread and butter.

Many national 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." This conceit is elaborated in a one-paragraph story by Jorge Luis Borges and Adolfo Bioy Casares, generally known in English as "On Exactitude in Science".

Orientation

Usually North is up, but not on a polar map, and see also Dymaxion map.

On a map we have in clockwise direction forward, right, backward, and left. Occasionally a map is on a ceiling, correctly showing directions; in that case, looking up we have in clockwise direction forward, left, backward, and right. If the map is prepared on a table, to be attached to the ceiling, then on the table it is a mirror image of a normal map.

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.

Combinations are possible, e.g. the second applying for text and the third for the outline of a map feature such as a forest, a building etc. Also the map may have layers which are partly raster graphics and partly vector graphics.

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.

Web maps are typically handled by a Geographic information system which does the spatial data processing necessary to handle different coordinate system and spatial relations between different kinds of data. GIS does a lot more than make maps, though.

References

  • David Buisseret, ed., Monarchs, Ministers and Maps: The Emergence of Cartography as a Tool of Government in Early Modern Europe. Chicago: University of Chicago Press, 1992, [ISBN 0226079872]
  • Miles Harvey, The Island of Lost Maps: A True Story of Cartographic Crime. New York : Random House, 2000. [ISBN 0767908260, cited above; also ISBN 0375501517]
  • Mark Monmorier, How to Lie with Maps, [ISBN 0226534219]

See also

Wikimedia Commons has media related to maps.

Public domain resources

General

Wikipedia:Proposed syntax for standard maps and Wikipedia:Map
Retrieved from "https://en.wikipedia.org/w/index.php?title=Map&oldid=9874834"