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A diagram of a typical nautical sextant, a tool used in celestial navigation to measure the angle between two objects viewed by means of its optical sight. Celestial navigation, also known as astronavigation, is the practice of position fixing using stars and other celestial bodies that enables a navigator to accurately determine their actual current physical position in space or on the ...
Sextant. A sextant is a doubly reflecting navigation instrument that measures the angular distance between two visible objects. The primary use of a sextant is to measure the angle between an astronomical object and the horizon for the purposes of celestial navigation . The estimation of this angle, the altitude, is known as sighting or ...
v. t. e. A geographic coordinate system ( GCS) is a spherical or geodetic coordinate system for measuring and communicating positions directly on Earth as latitude and longitude. [ 1] It is the simplest, oldest and most widely used of the various spatial reference systems that are in use, and forms the basis for most others.
v. t. e. The Universal Transverse Mercator ( UTM) is a map projection system for assigning coordinates to locations on the surface of the Earth. Like the traditional method of latitude and longitude, it is a horizontal position representation, which means it ignores altitude and treats the earth surface as a perfect ellipsoid.
Geodetic latitude and geocentric latitude have different definitions. Geodetic latitude is defined as the angle between the equatorial plane and the surface normal at a point on the ellipsoid, whereas geocentric latitude is defined as the angle between the equatorial plane and a radial line connecting the centre of the ellipsoid to a point on the surface (see figure).
In other words, it is a line of longitude. The position of a point along the meridian is given by that longitude and its latitude , measured in angular degrees north or south of the Equator . On a Mercator projection or on a Gall-Peters projection , each meridian is perpendicular to all circles of latitude .
World map. 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.
Graticule (cartography) A graticule (from Latin crāticula 'grill/grating'), on a map, is a graphical depiction of a coordinate system as a grid of lines, each line representing a constant coordinate value. [ 1 ] It is thus a form of isoline, and is commonly found on maps of many kinds, at scales from local to global.