Map types and projections Map

map of large underwater features. (1995, noaa)

maps of world or large areas either political or physical . important purpose of political map show territorial borders; purpose of physical show features of geography such mountains, soil type or land use including infrastructure such roads, railroads , buildings. topographic maps show elevations , relief contour lines or shading. geological maps show not physical surface, characteristics of underlying rock, fault lines, , subsurface structures. maps depict surface of earth use projection, way of translating three-dimensional real surface of geoid two-dimensional picture. perhaps best-known world-map projection mercator projection, designed form of nautical chart. aeroplane pilots use aeronautical charts based on lambert conformal conic projection, in cone laid on section of earth mapped. cone intersects sphere (the earth) @ 1 or 2 parallels chosen standard lines. allows pilots plot great-circle route approximation on flat, two-dimensional chart.

azimuthal or gnomonic map projections used in planning air routes due ability represent great circles straight lines.
richard edes harrison produced striking series of maps during , after world war ii fortune magazine. these used bird s eye projections emphasise globally strategic fronts in air age, pointing out proximities , barriers not apparent on conventional rectangular projection of world.

electronic maps

a usgs digital raster graphic.

from last quarter of 20th century, indispensable tool of cartographer has been computer. of cartography, @ data-gathering survey level, has been subsumed geographic information systems (gis). functionality of maps has been advanced technology simplifying superimposition of spatially located variables onto existing geographical maps. having local information such rainfall level, distribution of wildlife, or demographic data integrated within map allows more efficient analysis , better decision making. in pre-electronic age such superimposition of data led dr. john snow identify location of outbreak of cholera. today, used agencies of human kind, diverse wildlife conservationists , militaries around world.

relief map sierra nevada

even when gis not involved, cartographers use variety of computer graphics programs generate new maps.

interactive, computerised maps commercially available, allowing users zoom in or zoom out (respectively meaning increase or decrease scale), replacing 1 map of different scale, centered possible on same point. in-car global navigation satellite systems computerised maps route-planning , advice facilities monitor user s position of satellites. computer scientist s point of view, zooming in entails 1 or combination of:

a world map in pdf format.

for example:

typically (2) applies portable document format (pdf) file or other format based on vector graphics. increase in detail is, of course, limited information contained in file: enlargement of curve may result in series of standard geometric figures such straight lines, arcs of circles or splines.
(2) may apply text , (3) outline of map feature such forest or building.
(1) may apply text needed (displaying labels more features), while (2) applies rest of image. text not enlarged when zooming in. similarly, road represented double line may or may not become wider when 1 zooms in.
the map may have layers partly raster graphics , partly vector graphics. single raster graphics image (2) applies until pixels in image file correspond pixels of display, thereafter (3) applies.

see also: webpage (graphics), pdf (layers), mapquest, google maps, google earth, openstreetmap or yahoo! maps.