accuracy, map
The degree to which a value, or set of values, either measured or calculated, approximates a specified standard for that value. In cartography, it is a measure of how close the coordinates of points on a map compare with known survey coordinates (ground truth data). (Accuracy is not to be confused with the term "precision", which refers to the quality of the method used to take the measurement). (See precision).
The process of taking photographs from a camera mounted in an airplane or balloon. The resulting photographs may be classified as vertical or oblique depending on the angle of the camera with respect to the Earth's surface at the time of exposure. Aerial photographs are used extensively in cartography to provide detailed geographical information in the production of base maps.
aeronautical chart
A chart or map used for air navigation, which provides the aircraft pilot with important information about flight paths, airport approaches and facilities, as well as landmark features. In Canada, the federal government agency responsible for the supply of aeronautical information is the Aeronautical Charts Service URL, of Geomatics Canada, Natural Resources Canada.
alidade
That part of a surveying instrument which consists of a sighting device and index, with accessories for reading and recording data. A telescopic alidade is part of a theodolite or surveyor's transit, and when mounted on a straightedge, in conjunction with a plane-table, is used in topographic surveying. (See theodolite and transit).
alphanumeric grid
Any systematic pattern of lines superimposed on a map, in which one group of lines is labeled numerically while the other group of lines is labeled alphabetically. The resultant 2-dimensional grid allows the map user to define the approximate location of geographical features. (Also called an atlas grid).
altitude tints (see
hypsometric tints)
analogue (see data)
analysis (see spatial
analysis)
Antarctic Circle
A line of latitude at 66° 33' South, when shown as a fixed position on a map, delineates a region, which at the time of the winter solstice (in the Northern Hemisphere), the Sun is above the horizon at local midnight time at all points in this region. (Also the complement of the Tropic of Capricorn, which lies at latitude 23° 27' South).
Arctic Circle
A line of latitude at 66° 33' North, when shown as a fixed position on a map, delineates a region, which at the time of the summer solstice (in the Northern Hemisphere), the Sun is above the horizon at local midnight time at all points in this region. Also the complement of the Tropic of Cancer, which lies at latitude 23° 27' North.
area
A clearly defined 2-dimensional geometric region, having length and width, but not height or depth. For example, a census division, lake, or province (any geographically defined surface). A measurement in square units of a closed surface. (See polygon).
aspect
The orientation or position of a map projection graticule in respect to the lines of latitude and longitude on the globe they are representing. For example, the planar family of projections may be grouped into three aspects: polar, equatorial and oblique. (The term case", is also used in cartographic literature).
astrolabe
A navigational instrument used to measure the vertical angle between the horizon or the horizontal plane at the observer, and a celestial feature. An astrolabe is used to determine the geographic coordinates of points on the Earth's surface.
atlas
A collection of maps in book or loose-leaf form, with a standard design, organized around a coherent theme. For example, a world atlas, a national atlas, or an historical atlas.
attribute
In GIS technology, a characteristic of a geographical feature described in numbers or words. Attributes are usually stored in a table, with each column or field representing a characteristic, and each row or record being a different feature. (See field and record).
automated cartography
The process of producing maps using a computer-based system, (digital technology) to improve efficiency and to facilitate the speedier revision of the geographical information they portray. These computer systems often replace many manual tasks associated with cartographic production. Automated cartography is not to be confused with GIS. (See GIS, Geographic Information System).
axis
(1) A line about which the Earth or a globe rotates. (2) In respect to a spherical coordinate system, the line to which directions are related and from which angles are measured. (3) Also, a line along which measurements are made in order to determine the coordinates of a location.
azimuth
From the Arabic, "al-samt" meaning the way, the direction or the arc. A horizontal angle of direction calculated clockwise from the meridian plane. Azimuthal compass direction is expressed in terms of all 360° of a circle. The term can also be called magnetic azimuth, when calculated using the North or South magnetic poles.
azimuth degree
A unit of direction, representing 1/360 of a full circle.
azimuthal map projections (see planar map projections)