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Glossary Search Results
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- DCW -Digital Chart of the World
- A digital cartographic data base of the World, developed by the United States Defense Mapping Agency (DMA), with the cooperation of Australia, Canada and the United Kingdom, to support the display and analysis of geographic data. It is generally based on the DMA's 1:1 000 000 scale Operational Navigation Chart (ONC), base map series. The data is in vector form and is suitable for GIS applications.
- Dairy
- Milk processing plant.
- Dairy farm
- A farm reporting any number of dairy cows.
- Dairy year
- The dairy year, which runs from August 1 to July 31 of the following year, is timed so that the annual supply management quota period starts after the peak summer production period.
- Data
- A collection (set) of isolated facts or information. Data can be analogue (expressed in terms of physical quantities such as voltage, weight, distance to represent numbers) or digital (the magnitude of a mathematical measurement represented by digits or numbers). Data may be referred to as measured, observed, calculated or raw. The plural of datum.
- Data base
- A set or collection of interrelated data stored and managed for a particular project. A data base can be stored in machine readable form (on magnetic tape, disk or optical disk) or it can be on paper (as in a book). The same as a data bank except that the data is for a specific project. Data base can also mean a collection of information or material (in digital or analogue form) such as an archive or library.
- Date Line
- (See International Date Line)
- Datum
- (1) In general terms, a single isolated piece of information.
(2) A fixed reference point or basis to which other information is related.
(3) A set of accurately surveyed horizontal control points that define the shape of the Earth as a spheroid and form the basis for a 2-dimensional coordinate system.
(4) A vertical datum is a level surface of reference (usually mean sea level or the geoid) from which elevations are measured. (See -North American Datum 1983 (NAD 83) and Spheroid).
- Dead reckoning
- The calculation of a ship or aircraft's location by using the last recorded location and the measurement of its speed and drift. Dead reckoning is used when no other observations are possible.
- Declination
- (1) In geometry, for a spherical coordinate system, the angle at the centre of a sphere between the equatorial plane and a line to a point on the sphere.
(2) The arc between the Equator and a point on a great circle perpendicular to the Equator.
(3) In astronomy, the angular distance of a star or planet above or below the celestial Equator.
(4) Magnetic declination is the angle between true (geographic) north and magnetic North (the direction of the magnetic compass needle), from the point of observation. This angle varies for different locations and continually changes with time due to the wandering of the magnetic north pole.
(5) Grid declination is the angle between grid north on a grid reference system (e.g. U.T.M. Grid or Military Grid) and true (geographic) north. (In navigation, the term variation is also used).
- Deforestation
- Those practices or processes that result in the conversion of forested lands to non-forest uses. (Source: Government of Canada Climate Change Site, Glossary of Climate Change Terms)
- Degree
- (1) A unit of angular or circular-arc measurement equal to 1/90 of a right angle or 1/360 of a circle.
(2) A unit of measurement used to express latitude and longitude in a spherical grid reference system.
(3) An arbitrary unit of measurement also used in scales of temperature, hardness, and other phenomena.
- Demographic map
- A thematic map depicting the phenomena of human population, such as size, distribution, density, and condition.
- Density
- (1) The number of objects per areal unit.
(2) In photography, the opaqueness of an image.
- Depression contour
- An isoline drawn on a map, inside of which the land is at a lower elevation than the land area outside this line. Depression contours are usually drawn with tick marks spaced out along their length on the inside of the lower area.
- Desertification
- The process of degrading of the biological potential of land from a combination of adverse climate and excessive human exploitation, leading ultimately to desert-like conditions. (Source: United Nations Development Programme, Global Environment Facility, Country Dialogue Workshops Programme, Glossary of Terms)
- Developable shape
- A geometric shape that can be flattened without stretching or compressing its surface. Examples of these shapes are the cone, cylinder and plane. Many map projections are produced, described and classified in terms of these shapes. (See Undevelopable surface).
- Diazo process
- A rapid and inexpensive method of copying maps or documents in which a positive opaque original image (on a transparent or translucent base) is contacted with a paper, presensitized with a diazo compound (complex aromatic chemical compounds which have the property of combining with other substances in an alkaline environment to produce azo dyes). Exposure to a strong ultraviolet light decomposes the diazo compound on the non-image area of the paper. Finally, ammonia fumes develop the latent image of the unexposed diazo compound.
- Digital cartography
- (See Automated cartography)
- Digital data
- (See Data)
- Digital terrain model
- A topographic surface or computer representation of terrain stored in a digital data file as a set of 3-dimensional ("x,y,z") coordinates. The image may be displayed on a computer monitor or portrayed on a map. Also called a digital elevation model (DEM).
- Digitize
- The process of converting a continuous signal of data in analogue form into a stream of "x,y" or "x,y,z" coordinates, by using a digitizer. A digitizer is a computer based system including a table and cursor used to record the coordinates of map features.
- Direction
- (See Bearing)
- Discharge
- In the simplest form, discharge means outflow of water. The use of this term is not restricted as to course or location, and it can be used to describe the flow of water from a pipe or from a drainage basin. Related terms are runoff, streamflow, and yield.
- Dispersed Stores
- Those stores within a census metropolitan area or census agglomeration that are not allocated to one of the five types of commercial polygons.
- Distance
- The fundamental spatial concept of the amount of space between non-connected points. Not to be confused with length, as length always implies a physical connection.
- Distortion
- The result of changing the shape of a figure from its original form. In the process of map projection the shape, distance, area and angles of features on the curved surface of the Earth are stretched or compressed in order to retain their positional accuracy on a flat map.
- Distribution map
- A thematic map showing the geographic occurrence of a particular item, feature, or event. Both qualitative and quantitative data may be depicted in this manner, the information being symbolized in many ways. (See Dot map).
- Divorced
- Persons who have obtained a legal divorce and who have not remarried. (Source: 1996 Census Dictionary, Statistics Canada)
- Domestic use
- The quantity of water used for household purposes such as washing, food preparation, and bathing.
- Dot map
- A distribution map showing a spatial pattern by placing dots in a specific area, each dot representing a specific value or quantity of the subject being shown. The "dots" can be symbols of various shapes and they can be in differing sizes (in which case they are known as proportional symbols).
- Dot screen
- A photographic film covered with uniformly sized and evenly spaced dots; used to break-up a solid colour to produce an apparent lighter colour. The apparent lightness or darkness of the colour may be changed by selecting screens with different sized dots. This difference is expressed as a percentage. (e.g., a 40% screen would have 60% of its surface covered by opaque dots allowing only 40% of a colour to be transmitted).
- Downtown
- The concentration of commercial activities that serve the whole urban region, including specialized retail, financial, and business services, as well as public sector facilities. These activities may be organized into subareas according to function and market. Typically, downtown is the oldest part of the city, and the most accessible location overall.
- Drafting
- The process of preparing cartographic reproduction material by means of drawing with pencil, pen and ink, or scribing according to specifications. (See Specifications ("specs")).
- Drainage
- In cartography, all features on a map associated with water, for example, rivers, lakes, shoreline or marshes.
- Drainage basin
- A drainage basin is the area that drains all precipitation received as runoff and base flow (groundwater sources) into a river or stream system into a common outlet such as a lake or sea.
- Drought
- An extended period of dry weather sufficiently prolonged for the lack of moisture to cause a serious hydrological imbalance (i.e. crop damage, water-supply shortage, etc.) in the affected area. (Source: Government of Canada Climate Change Site, Glossary of Climate Change Terms)
- Drum scanner
- A type of scanner in which a map, diagram or photograph is placed on a cylinder which rotates slowly while a scanning beam quickly moves back and forth parallel to the revolving image. At the same time, the "x,y" coordinates and spectral signature of each element of the image are recorded. (See Scanner).
- Dryland
- A type of farming that depends only on natural precipitation and soil moisture to water crops (i.e. non-irrigated). (Source: Agriculture and Agrifood Canada).
- Dwelling, Occupied Private
- Refers to a private dwelling in which a person or a group of persons are permanently residing. Also included are private dwellings whose usual residents are temporarily absent on Census Day. Unless otherwise specified, all data in housing reports are for occupied private dwellings rather than unoccupied private dwellings or dwellings occupied solely by foreign and/or temporary residents. (Source: 1996 Census Dictionary, Statistics Canada)
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