Map projection in the context of "Longitude"

A world map is a map of most or all of the surface of Earth. World maps, because of their scale, must deal with the problem of projection. Maps rendered in two dimensions by necessity distort the display of the three-dimensional surface of the Earth. While this is true of any map, these distortions reach extremes in a world map. Many techniques have been developed to present world maps that address diverse technical and aesthetic goals.

Charting a world map requires global knowledge of the Earth, its oceans, and its continents. From prehistory through the Middle Ages, creating an accurate world map would have been impossible because less than half of Earth's coastlines and only a small fraction of its continental interiors were known to any culture. With exploration that began during the European Renaissance, knowledge of the Earth's surface accumulated rapidly, such that most of the world's coastlines had been mapped, at least roughly, by the mid-1700s and the continental interiors by the twentieth century.

Maps have been one of the most important human inventions, allowing humans to explain and navigate their way. When and how the earliest maps were made is unclear, but maps of local terrain are believed to have been independently invented by many cultures. The earliest putative maps include cave paintings and etchings on tusk and stone. Maps were produced extensively by ancient Babylon, Greece, Rome, China, and India.

The earliest maps ignored the curvature of Earth's surface, both because the shape of the Earth was unknown and because the curvature is not important across the small areas being mapped. However, since the age of Classical Greece, maps of large regions, and especially of the world, have used projection from a model globe to control how the inevitable distortion gets apportioned on the map.

90°N 0°E / 90°N 0°E / 90; 0

The North Pole, also known as the Geographic North Pole or Terrestrial North Pole, is the point in the Northern Hemisphere where the Earth's axis of rotation meets its surface. It is called the True North Pole to distinguish from the Magnetic North Pole.

In modern mapping, a topographic map or topographic sheet is a type of map characterized by large-scale detail and quantitative representation of relief features, usually using contour lines (connecting points of equal elevation), but historically using a variety of methods. Traditional definitions require a topographic map to show both natural and artificial features. A topographic survey is typically based upon a systematic observation and published as a map series, made up of two or more map sheets that combine to form the whole map. A topographic map series uses a common specification that includes the range of cartographic symbols employed, as well as a standard geodetic framework that defines the map projection, coordinate system, ellipsoid and geodetic datum. Official topographic maps also adopt a national grid referencing system.

Natural Resources Canada provides this description of topographic maps:

An orthophoto, orthophotograph, orthoimage or orthoimagery is an aerial photograph or satellite imagery geometrically corrected ("orthorectified") such that the scale is uniform: the photo or image follows a given map projection. Unlike an uncorrected aerial photograph, an orthophoto can be used to measure true distances, because it is an accurate representation of the Earth's surface, having been adjusted for topographic relief, lens distortion, and camera tilt.

Orthophotographs are commonly used in geographic information systems (GIS) as a "map accurate" background image. An orthorectified image differs from rubber sheeted rectifications as the latter may accurately locate a number of points on each image but stretch the area between so scale may not be uniform across the image. A digital elevation model (DEM) or topographic map is required to create an orthophoto, as distortions in the image due to the varying distance between the camera/sensor and different points on the ground need to be corrected. An orthoimage and a "rubber sheeted" image can both be said to have been georeferenced; however, the overall accuracy of the rectification varies. Software can display the orthophoto and allow an operator to digitize or place linework, text annotations or geographic symbols (such as hospitals, schools, and fire stations). Some software can process the orthophoto and produce the linework automatically.

The Mollweide projection is an equal-area, pseudocylindrical map projection generally used for maps of the world or celestial sphere. It is also known as the Babinet projection, homalographic projection, homolographic projection, and elliptical projection. The projection trades accuracy of angle and shape for accuracy of proportions in area, and as such is used where that property is needed, such as maps depicting global distributions.

The projection was first published by mathematician and astronomer Karl (or Carl) Brandan Mollweide (1774–1825) of Leipzig in 1805. It was reinvented and popularized in 1857 by Jacques Babinet, who called it the homalographic projection. The variation homolographic arose from frequent nineteenth-century usage in star atlases.

A graticule or grid (from Latin crāticula 'grill/grating'), on a map, is a graphical depiction of a coordinate system as a grid of coordinate curves or "lines", each curve/line representing a constant coordinate value. It is thus a form of isoline, and is commonly found on maps of many kinds, at scales from local to global.

The term graticule is almost always used to specifically refer to the parallels and meridians of latitude and longitude, respectively. In modern usage, graticules are contrasted with grids, which display the eastings and northings of a projected coordinate reference system, such as Universal Transverse Mercator – usually the coordinate system in which the map is drawn.