Cartographic Terms

Accuracy

Accuracy

Degree of conformity with a standard. Accuracy relates to the quality of a result and is distinguished from precision which relates to the quality of the operation by which the result is obtained.

Adjustment

Process designed to remove inconsistencies in measured or computed quantities by applying derived corrections to compensate for random or accidental errors.

Adjustment, land

line - Positioning land lines on a map to indicate their true, theoretical, or approximate location relative to the adjacent terrain and culture, by reconciling the information shown on Bureau of Land Management plats and field records with the ground evidence of the location of the lines.

Adjustment, standard accuracy

Adjustment of a survey resulting in values for positions and (or) elevations that comply with the National Map Accuracy Standards.

Aerotriangulation

The process of developing a network of horizontal and or vertical positions from a group of known positions using direct or indirect measurements from aerial photographs and mathematical computations.

Alidade

Instrument, or part of an instrument , for determining direction , either horizontal or vertical . In its simplest form, a peepsight or telescope mounted on a straightedge and used for plotting directions graphically. In such instruments as transits and theodolites, the alidade is the part containing the telescope and its attachments.

Altimeter

Instrument for measuring altitudes or elevations with respect to a reference level, usually mean sea level. The most common type is an aneroid barometer. A radar altimeter determines the height of an aircraft above the terrain by measuring the time required for an electromagnetic pulse to travel from aircraft to the ground and back.

Azimuth

Horizontal direction reckoned clockwise from the meridian plane.

Backshore

Part of a beach that is usually dry and is reached only by the highest tides; by extension, a narrow strip of relatively flat coast bordering the sea.

Base map

See: map, base.

Bathymetric map

See: map, bathymetric

Bathymetry

Science of measuring water depths (usually in the ocean) to determine bottom topography.

Beach (seabeach)

Zone of unconsolidated material that extends landward from the low water line to the place where there is marked change in material or physiographic form, or to the line of permanent vegetation (usually the effective lint of storm waves).

Bench mark

Relatively permanent material object, natural or artificial, bearing a marked point whose elevation above or below an adopted datum is known.

Boundary monument

Material object placed on or near a boundary line to preserve and identify the location of the boundary line on the ground

Boundary survey

Survey made to establish or to reestablish a boundary line on the ground, or to obtain data for constructing a map or plat showing a boundary line.

Cadastral map

See: map, cadastral.

Cadastral survey

Survey relating to land boundaries, made to create units suitable for title transfer or to define the limitations of title. Derived from "cadastre" meaning a register of land quantities, values, and ownership used levying taxes, the term may properly be applied to surveys of a similar nature outside the public lands, and such surveys are more commonly called "land surveys or property surveys."

Cartography

Science and art of making maps a charts. The term may be taken broadly as comprising all the steps needed to produce a map: planning, aerial photography, field surveys, photogrammetry, editing, color separation, and multicolor printing. Mapmakers, however, tend to limit use of the term to the map- finishing operations, in which the master manuscript is edited and color separation plates are prepared for lithographic printing.

Chain

Unit of length equal to 66 feet, used especially in the U.S. public land surveys. The original measuring instrument (Gunter's chain) was literally a chain consisting of 100 iron links, each 7.92 inches long.Steel-ribbon tapes began to supersede chains around 1900, but surveying tapes are often still called "chains" and measuring with a tape is often called "chaining."

Chain

is a convenient unit in cadastral surveys because 10 square chains equal 1 acre.

Chart

Special-purpose map designed for navigation or to present specific data or information. The term is applied chiefly to maps made primarily for nautical and aeronautical navigation, and to maps of the heavens, although the term is sometimes used to describe other special-purpose maps.

chart, aeronautical

Charts designed to meet requirements of aerial navigating, produced in several series, each on a specified map projection and differing in scale, format, and content, for use as dictated by type of aircraft and whether flight is to be conducted under visual or instrument flight rules.

chart, bathymetric

See: map, bathymetric

chart, nautical

Representation of a portion of the navigable waters of the Earth and adjacent coastal areas on a specified map projection and designed specifically to meet requirements for marine navigation.

Nautical Charts

Included are depths of water, characteristics of the bottom, elevations of selected topographic features, general configurations and characteristics of the coast, the shoreline (usually the mean high water line), dangers, obstructions and aids to navigation limited tidal data, and information about magnetic variation in the charted area.

Choropleth map

See: map, choropleth

Clinometric map

See: map, slope

Color separation

Process of preparing a separate drawing, engraving, or negative for each color required in the printing production of a map or chart.

Compilation

Preparation of a new or revised map or chart, or portion thereof, from existing maps, aerial photographs, field surveys, and other sources.

Continuous tone

Image not broken into dots by photographic screen; contains unbroken gradient tones from black to white, and may be either in negative or positive form.

Aerial photographs

are examples of continuous- tone prints. Contrasted with halftone (screened) and line copy.

Contour

Imaginary line on ground, all points of which are at the same elevation above or below a specific datum.

Contour interval

Difference in elevation between two adjacent contours.

Control mapping

Points of established position or elevation, or both, which are used to fix references in positioning and correlating map features.

Fundamental control

is provided by stations in the national networks of triangulation and traverse (horizontal control) and leveling (vertical control). Usually it is necessary to extend geodetic surveys, based on fundamental stations, over the area to be mapped, to provide a suitable density and distribution of control points.

Supplemental control points

are those needed to relate the aerial photographs used for mapping with the system of ground control. These points must be positively photoidentified; that is, the points must be positively correlated with their images on the photographs.

Control station

Point on the ground whose position (horizontal or vertical) is known and can be used as a base for additional survey work.

Coordinates

Linear and (or) angular quantities that designate the position of a point in relation to a given reference frame.

Coordinates, origin of

Points in a system of coordinates which serves as a zero point in computing the system's elements or in prescribing its use.

Culture

Features constructed by man that are under, on, or above the ground which are delineated on a map. These include roads, trails, buildings, canals, sewer systems, and boundary lines. In a broad sense, the term also applies to all names, other identification, and legends on a map.

Datum (pl. datums)

In surveying, a reference system for computing or correlating the results of surveys.

Vertical and Horizontal datum

two principal types of datums.

Vertical datum

is a level surface to which heights are referred. In the United States, the generally adopted datum for leveling operations is the National Geodetic Vertical Datum of 1929.

Horizontal datum

is used as a reference for position.

The North American Datum of 1927

is defined by the latitude and longitude of an initial point (Meade's Ranch in Kansas), the direction of a line between this point and a specified second point, and two dimensions that define the spheroid.

The new North American Datum of 1983

is based on a newly defined spheroid (GRS80); it is an Earth-centered datum having no initial point or initial direction.

Datum, national geodetic vertical

See: national geodetic vertical datum of 1929

Declination

In astronomy, the angular distance of a celestial body above (north, plus) or below (south, minus) the celestial Equator.

Magnetic declination

is the angular difference between magnetic north and true (geographic) north at the point of observation; it is not constant but varies with time because of the "wandering" of the magnetic north pole.

Depth curve

Line on a map or chart connecting points of equal depth below the datum.

Diazo process

Rapid method for copying documents in which the image is developed by exposure to ammonia.

Dike

Bank of earth or stone used to form a barrier, frequently and confusingly interchanged with levee. This restrains water within an area that normally is flooded. See levee.Electronic distance measuring (EDM) device - Instruments that measure the phase difference between transmitted and reflected or retransmitted electromagnetic waves of known frequency, or that measure the round-trip transit time of a pulsed signal, from which distance is computed.

Elevation

Vertical distance of a point above or below a reference surface or datum.

Ellipsoid

See: spheroid

Engineering map

See: map, engineering

ER

55 plotter - Double-projection plotting instrument utilizing ellipsoidal reflectors for light projection.

Erosion

Group of natural processes including weathering, dissolution, abrasion, corrosion, and transportation that remove material from any part of the Earth's surface.

Estuary

That portion of a stream influenced by the tide of the body of water into which it flows; an arm of the sea at a river mouth.

Feature separation

Process of preparing a separate drawing, engraving, or negative for selected types of data in the preparation of a map or chart.

flood control map

See: map, flood control

flood plain

Belt of low flat ground bordering a stream channel that is flooded when runoff exceeds the capacity of the stream channel.

forestry map

See: map, forestry

formlines

Lines, resembling contour lines, drawn to present a conception of the shape of the terrain without regard to a true datum or regular spacing.

Geodesy

Science concerned with the measurement and mathematical description of the size and shape of the earth and its gravitational fields.

Geodesy

also includes the large-scale, extended surveys for determining positions and elevations of points, in which the size and shape of the earth must be taken into account.

Geoid

Figure of the Earth visualized as a mean sea level surface extended continuously through the continents. It is a theoretically continuous surface that is perpendicular at every point to the direction of gravity (the plumbline).

geologic map

See: map, geologic

Graticule

Network of parallels and meridians on a map or chart.

graticule, geographic

System of coordinates of latitude and longitude used to define the position of a point on the surface of the Earth with respect to the reference spheroid.

Grid

Network of uniformly spaced parallel lines intersecting at right angles. When superimposed on a map, it usually carries the name of the projection used for the map- that is, Lambert grid, transverse Mercator grid, universal transverse Mercator grid.

Hachure

Any series of lines used on a map to indicate the general direction and steepness of slopes. The lines are short, heavy, and close together for steep slopes; longer, lighter, and more widely spaced for gentle slopes.

Halftone

A picture in which the gradations of light are obtained by the relative darkness and density of tiny dots produced by photographing the subject through a fine screen.

high water

Maximum height reached by a rising tide. The height may be due solely to the periodic tidal forces or it may have superimposed upon it the effects of prevailing meteorological conditions. Use of the "high tide" is discouraged.

high water line

Intersection of the land with the water surface at an elevation of high water.

high water mark

Line or mark left upon tidal flats, beach, or along shore objects indicating the elevation or the intrusion of high water.

hydrographic survey

Survey of water area, with particular reference to submarine relief, and any adjacent land. See: oceanographic survey

hydrography

Science that deals with the measurement and description of the physical features of the oceans, seas, lakes, rivers, and their adjoining coastal areas, with particular reference to their use for navigation.

Hydrology

Scientific study of the waters of the Earth, especially with relation to the effects of precipitation and evaporation upon the occurrence and character of ground water.

hypsographic map

See: map, hypsographic

hypsography

Topography referred to the national geodetic vertical datum of 1929. The science or art of describing heights of land surfaces with reference to this datum.

hypsometric map

See: map, hypsometric

hypsometry

Science or art of determining terrain relief, by any method.

Imagery

Visible representation of objects and (or) phenomena as sensed or detected by cameras, infrared and multispectral scanners, radar, and photometers. Recording may be on photographic emulsion (directly as in a camera or indirectly after being first recorded on magnetic tape as an electrical signal) or on magnetic tape for subsequent conversion and display on a cathode ray tube.

infrared scanner (thermal mapper)

Instrument that detects infrared radiation and converts the detected energy to an electrical signal for recording on photographic film or magnetic tape.

isogonic chart

Chart showing isogonic lines properly labeled with their magnetic declination.

isogonic line

Line joining points on the Earth's surface having equal magnetic declination as of a given date.

isopleth map

See: map, isopleth

Kelsh plotter

Double-projection plotting instrument utilizing swinging lamps to transmit light through contact- size diapositives (positive transparencies).

land use classification system

Coding system of categories and subcategories designed for use on a map to designate land or water use.

land use map

See: map, land use

landmark

Monument of material mark or fixed object used to designate a land boundary on the ground: any prominent object on land that may be used to determine a location or a direction in navigation or surveying.

Latitude

Angular distance, in degrees, minutes, and seconds of a point north or south of the Equator.

lead line

Line weighted with lead for making depth soundings in water.

Levee

Artificial bank confining a stream channel or limiting adjacent areas subject to flooding; an embankment bordering a submarine canyon or channel, usually occurring along the outer edge of a curve.

level surface

Surface which at every point is perpendicular to the plumbline or the direction in which gravity acts.

Leveling

Surveying operation in which heights of objects and points are determined relative to a specified datum. line copy (line drawing) Map copy suitable for reproduction without the use of a screen; a drawing composed of lines as distinguished from continuous- tone copy.

line map

See: map, line

longitude

Angular distance, in degrees, minutes, and seconds, of a point east or west of the Greenwich meridian.

low water

Minimum height reached by a falling tide. The height may be due solely to the periodic tidal forces or it may have superimposed upon it the effects of meteorological conditions.