Maps
A map is a visual representation of an area—a symbolic depiction highlighting relationships between elements of that space such as objects, regions, and themes. Many maps are static two-dimensional, geometrically accurate representations of three-dimensional space, while others are dynamic or interactive, even three-dimensional. Although most commonly used to depict geography, maps may represent any space, real or imagined, without regard to context or scale; e.g. Brain mapping, DNA mapping, and extra-terrestrial mapping. Cartography, or map-making is the study and, often, practice, of crafting representations of the Earth upon a flat surface (see History of cartography), and one who makes maps is called a cartographer. 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 terms of quantity, the largest number of drawn map sheets is probably made up by local surveys, carried out by municipalities, utilities, tax assessors, emergency services providers, and other local agencies. Many national surveying projects have been carried out by the military, such as the British Ordnance Survey (now a civilian government agency internationally renowned for its comprehensively detailed work).
A map can also be any document giving information as to where or what something is. The term orientation refers to the relationship between directions on a map and compass directions. The word orient is derived from oriens, meaning east. In the Middle Ages many maps, including the T and O maps, were drawn with east at the top. Today the most common, but far from universal, cartographic convention is that North is at the top of a map. Examples of maps not oriented to north are: Reversed maps, also known as Upside-Down maps or South-Up maps, which generally show Australia and New Zealand at the top of the map instead of the bottom. Polar maps of the Arctic or Antarctic regions are conventionally centered on the pole, in which case the direction north would be towards or away from the center of the map, respectively. Buckminster Fuller's Dymaxion maps are based on a projection of the Earth's sphere onto an icosahedron. The resulting triangular pieces may be arranged in any order or orientation.
Maps from non-Western traditions are oriented a variety of ways. Old maps of Edo show the Japanese imperial palace as the "top, " but also at the centre, of the map.
Labels on the map are oriented in such a way that you cannot read them properly unless you put the imperial palace above your head. Medieval European T and O maps such as the Hereford Mappa Mundi were centred on Jerusalem with east at the top. Indeed, prior to the reintroduction of Ptolemy's Geography to Europe around 1400, there was no single convention in the West. Portolan charts, for example, are oriented to the shores they describe.
Route and channel maps have traditionally been oriented to the road or waterway they describe. Many maps used in the Society for Creative Anachronism show the west at the top, in honor of the Society starting in California.
Scale and accuracy: Many but not all maps are drawn to a scale, allowing the reader to infer the actual sizes of, and distances between, depicted objects. A larger scale shows more detail, thus requiring a larger map to show the same area.
For example, maps designed for the hiker are often scaled at the ratio 1:24, 000, meaning that 1 of any unit of measurement on the map corresponds to 24, 000 of that same unit in reality; while maps designed for the motorist are often scaled at 1:250, 000. Maps which use some quality other than physical area to determine relative size are called cartograms. A famous example of a map without scale is the London Underground map, which best fulfils its purpose by being less physically accurate and more visually communicative to the hurried glance of the commuter. This is not a cartogram (since there is no consistent measure of distance) but a topological map that also depicts approximate bearings. The simple maps shown on some directional road signs are further examples of this kind.
In fact, most commercial navigational maps, such as road maps and town plans, sacrifice an amount of accuracy in scale to deliver a greater visual usefulness to its user, for example by exaggerating the width of roads. With the end-user similarly in mind, cartographers will censor the content of the space depicted by a map in order to provide a useful tool for that user.
For example, a road map may or may not show railroads, and if it does, it may show them less clearly than highways. Some maps such as topographical maps show constant values such as elevation (or depression). These values are often represented, along with other characteristics, and depending on the scale of the map, in the form of Isolines. Isolines on a map or chart indicate a constant value such as temperature, or rainfall. Depending on the type of a map, alternative representations of elevation (or depression) exist as well. World maps and projections:
Map of large underwater features. (1995, NOAA)Maps of the world or large areas are often either 'political' or 'physical'.