Glossary of Cartography and Map Terminology Glossary of Cartography and Map Terminology Glossary of Cartography and Map Terminology GLOSSARY OF CARTOGRAPHY AND MAP TERMINOLOGY Definitions Provided By: Maps for America - Third Edition 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 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, such surveys are more commonly called "land surveys" or "property surveys." cartography Science and art of making maps and 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." The 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 "chart" 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. Included on most nautical charts 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, 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. There are tow principal types of datums: vertical and horizontal. A vertical datum is a level surface to which heights are referred. In the United States, the generally adopted vertical datum for leveling operations is the National Geodetic Vertical Datum of 1929. The 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. A dike 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 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 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 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 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. low water line Intersection of the land with the water surface at an elevation of low water. Not to be confused with mean low water line. magnetic declination See: declination map Graphic representation of the physical features (natural, artificial, or both) of a part or the whole of the Earth's surface, by means of signs and symbols or photographic imagery, at an established scale, on a specified projection, and with the means of orientation indicated. map, base Map on which information may be placed for purposes of comparison or geographical correlation. The term "base map" was at one time applied to a class of maps now known as outline maps. It may be applied to topographic maps, also termed "mother maps" that are used in the construction of other types of maps by the addition of particular data.

map, bathymetric Maps delineating the form of the bottom of a body of water, or a portion thereof, by the use of depth contours (isobaths). map, cadastral Map showing the boundaries of subdivisions of land, often with the bearings and lengths thereof and the areas of individual tracts, for purposes of describing and recording ownership. It may also show culture, drainage, and other features relating to land use and value. See: plat map, choropleth Thematic map in which areas are colored, shaded, dotted, or hatched to create darker or lighter areas in proportion to the density of distribution of the theme subject. map digitization Conversion of map data from graphic to digital form. map, engineering Map showing information that is essential for planning an engineering project or development and for estimating its cost. It usually is a large-scale map of a small area or of a route. It may be entirely the product of an engineering survey, or reliable information may be collected from various sources for the purpose, and assembled on a base map. map, flood control Map designed for studying and planning control projects in areas subject to flooding. map, forestry Map prepared principally to show the size, density, kind, and value of trees in a designated area.

map, geologic Map showing the structure and composition of geologic features. map hypsographic Map showing relief with elevations referred to the national geodetic vertical datum of 1929. map, hypsometric Map showing relief by any convention, such as contours, hachures, shading, or tinting. map, isopleth Map consisting of lines connecting places of equal value of distribution for a given theme such as rainfall or temperature. map, land use Map showing by means of a coding system the various purposes for which parcels of land are being used by man. map, line Map composed of lines as distinguished from photographic imagery. map, orthophotographic See: photomap map, planimetric Map that presents only the horizontal positions for features represented. distinguished from a topographic map by the omission of relief in measurable form. The features usually shown on a planimetric map include rivers, lakes, and seas; mountains, valleys, and plains; forests, and prairies; cities, farms transportation routes, and public utility facilities; and political and private boundary lines. A planimetric map intended for special use may present only those features essential to the purpose to be served.

map projection Orderly system of lines on a plane representing a corresponding system of imaginary lines on an adopted terrestrial or celestial datum surface. Also, the mathematical concept for such a system. For maps of the Earth, a projection consists of 1) a graticule of lines representing parallels of latitude and meridians of longitude or 2) a grid. map series Family of maps conforming generally to the same specifications and designed to cover an area or a country in systematic pattern. map, slope (clinometric map) Map showing the degree of steepness of the Earth's surface by the use of various colors or shading for critical ranges of slope. map, soil Map that shows the constitution, structure, and texture of the soil and identifies ongoing erosion. map, storm evacuation Map designed to identify coastal areas subject to flooding, to indicate recommended areas of refuge, and to emphasize available evacuation routes. map, thematic Map designed to provide information on a single topic, such as geology, rainfall, population. map, topographic Map that present the horizontal and vertical positions of the features represented; distinguished from a planimetric map by the addition of relief in measurable form.

marsh, coastal Area of salt-tolerant vegetation in brackish and (or) saline-water habitants subject to tidal inundation. marsh, freshwater Tract of low wet ground, usually miry and covered with rank vegetation. mean high water Tidal datum that is the arithmetic mean of the high water heights observed over a specific 19-year Metonic cycle (National Tidal Datum Epoch). For stations with shorter series, simultaneous observations are made with a primary control tide station to derive the equivalent of a 19-year value. Use of "mean high tide" is discouraged. mean high water line Intersection of the land with the water surface at the elevation of high water. See: shoreline mean low water Tidal datum that is the arithmetic mean of the low water heights observed over a specific 19-year Metonic cycle (National Tidal Datum Epoch). For stations with shorter series, simultaneous observations are made with a primary control tide station to derive the equivalent of a 19-year value. Use of "mean low tide" is discouraged. mean low water line Intersection of the land with the water surface at the elevation of low water.

mean sea level Tidal datum that is the arithmetic mean of the hourly water elevations observed over a specific 19-yearMetonic cycle (National Tidal Datum Epoch). Shorter series are specified in the name; that is, monthly mean sea level and yearly mean sea level. See: datum meander line Metes-and-bounds traverse approximately along the mean high water line of a permanent body of water. By following the sinuosities of the bank or shoreline, the meander line provides data for computing the area of land remaining after the water area has been segregated. A meander line differs from other metes and bounds surveys in that it does not ordinarily determine or fix boundaries. meanderable Capable of being depicted by reference to a meander line. meridian Great circle on the surface of the Earth passing through the geographical poles and any given point on the Earth's surface. All points on a given meridian have the same longitude. metes and bounds Method of describing land by measure of length (metes) of the boundary lines (bounds). Metonic cycle Period of 235 lunations or about 19 years.

devised by Meton, an Athenian astronomer (5th century B.C.) for the purpose of obtaining a period at the end of which the phases of the moon recur in the same order and on the same days as in the preceding cycle. metric system Decimal system of weights and measures based on the meter as a unit length and the kilogram as a unit mass. monoscopic Pertaining to the observation of a single photograph or other view. monument (surveying) Permanent physical structure marking the location of a survey point. Common types of monuments are inscribed metal tablets set in concrete posts; and metal rods driven in the ground. mosaic, aerial Assembly of aerial photographs whose edges usually have been torn or cut selectively and matched to the imagery on adjoining photographs to form a continuous representation of a portion of the Earth's surface. multiplex Stereoplotter of the double-projection type characterized by its use of reduced- scale diapositives and stationary lamphouses with condensing lenses. multispectral scanner (MSS) Device for sensing radian energy in several channels of the electromagnetic spectrum. national geodetic vertical datum of 1929 Reference surface established by the U.S.

Coast and Geodetic Survey in 1929 as the datum to which relief features and elevation data are referenced in the conterminous United States; formerly called "mean sea level 1929." National Map Accuracy Standards Specifications promulgated by the U.S. Office of Management and Budget to govern accuracy of topographic and other maps produced by Federal Agencies. navigable waters Water usable, with or without improvements, as routes for commerce in the customary means of travel on water. neatline Line separating the body of a map from the map margin. On a standard quadrangle map, the neatlines are the meridians and parallels delimiting the quadrangle. oceanic survey Survey or examination of condition in the ocean or any part of it, with reference to animal or plant life, chemical elements present, temperature gradients, etc. See: hydrographic survey offshore Comparatively flat zone of variable width that extends from the outer margin of the rather steeply sloping shoreface to the edge of the continental shelf. orientation Establishing correct relationship in direction with reference to points of the compass; the state of being in correct relationship in direction with reference to the points of the compass.

origin of coordinates Point in a system of coordinates that serves as a zero point in computing the system's elements or in prescribing its use. orthophotograph Photograph having the properties of an orthographic projection. It is derived from a conventional perspective photograph by simple or differential rectification so that image displacements caused by camera tilt and terrain relief are removed. orthophotographic map Map produced by assembling orthophotographs at a specified uniform scale in a map format. orthophotomap Orthophotographic map with contours and cartographic treatment, presented in a standard format, and related to standard reference systems. orthophotoquad Monocolor orthophotgraphic map presented in a standard quadrangle format and related to standard reference systems. It has no contours and little or cartographic treatment. orthophotoscope Photomechanical device used in conjunction with a double-projection stereoplotter for producing orthophotograph. overedge Any portion of a map lying outside the nominal map border (neatline). overlay Printing or drawing on a transparent or translucent medium intended to be placed in register on a map or other graphic and which shows details not appearing or requiring special emphasis on the base material.

overprint New material printed on a map or chart to show data of importance or special use, in addition to those data originally printed. parallel of latitude A circle, or approximation of a circle, on the surface of the Earth, parallel tot he Equator, and connecting points of equal latitude; a circle of the celestial sphere parallel to the ecliptic, and connecting points of equal celestial latitude. photogrammetry Science or art of obtaining reliable measurements or information from photographs or other sensing systems. photomap (photographic map) Map made by adding marginal information, descriptive data, and a reference system to a photograph or assembly of photographs. plain Region of uniform general slope, comparatively level, of considerable extent, and not broken by marked elevations and depressions (it may be an extensive valley floor or a plateau summit); an extent of level or nearly level land; a flat, gently sloping, or nearly level region of the sea floor. planetable Instrument consisting essentially of a drawing board on a tripod and some type of sighting device (alidade) with attached straightedge, used for plotting the lines of survey directly from observation in the field. planimetric map Plan details of a map - those having no indication of relief or contour.

plat Diagram drawn to scale showing all essential data pertaining to the boundaries and subdivisions of a tract of land, as determined by survey or protraction. As used by the Bureau of Land Management, the drawing which represents the particular area included in a survey, such as township, private land claim, or mineral claim, and the lines surveyed, established, or retraced, showing the direction and length of each such line; The relation to the adjoining official surveys; the boundaries, descriptions, and area of each parcel of land subdivided; and, as nearly as may be practicable, a representation of the relief and improvements within the limits of the survey. prime meridian Meridian of longitude 0 degrees, used as the origin for measurements of longitude. The meridian of Greenwich, England, is the internationally accepted prime meridian on most charts. However, local or national prime meridians are occasionally used. projection, map See: map, projection public land system Public lands are subdivided by a rectangular system of surveys established and regulated by the Bureau of Land Management. The standard format for subdivision is by townshipsmeasuring 6 miles (480 chains) on a side.

Townships are further subdivided into 36 numbered sections of 1 square mile (640 acres) each. quad-centered photograph Middle exposure of a phototriplet (three consecutive aerial photographs) take so that the middle photograph is exposed directly above the center of the quadrangle and the preceding and following photographs are exposed directly above the boundaries of the quadrangle. The flying height is set such that the quad-centered photograph covers the entire quadrangle. quadrangle Four-sided area, bounded by parallels of latitude and meridians of longitude used as an area unit in mapping (dimensions are not necessarily the same in both directions). Also, a geometric figure of significance in geodetic surveying. radial-line plotting Determination of the location of points by the successive intersection and resection of direction lines radiating from the radial centers of overlapping aerial photographs. rectification, differential The process of scanning and reprojecting a photograph onto a horizontal plane in differential elements to remove displacements caused by tilt and relief. The process may be accomplished by any one of a number of instruments developed specifically for the purpose.

rectification, simple Projection of an aerial photograph (mathematically, graphically, or photographically) from its plane onto a horizontal plane by translation, rotation, and (or) scale change to remove displacement due to tilt of the camera. relief Elevations and depressions of the land or sea bottom. relief shading Technique for making hypsography on a map appear three dimensional by the use of graded shadow effects. Generally, the features are shaded as though illuminated from the northwest. remote sensing Process of detecting and (or) monitoring chemical or physical properties of an area by measuring its reflected and emitted radiation. representational fraction Scale of a map or chart expressed as a fraction or ratio that relates unit distance on the map to distance measured in the same unit on the ground. reproduction Summation of all processes involved in printing copies from an original drawing. A printed copy of an original drawing made by the processes of reproduction scale Relationship existing between a distance on a map, chart, or photograph and the corresponding distance on the Earth. sea level (water level) Height of the surface of the sea at any given time.

section Unit of subdivision of a township; normally a quadrangle 1 mile square with boundaries conforming tomeridians and parallels within established limits, and containing 640 acres as nearly as practicable. sensor Technical means, usually electronic, to extend man's natural senses by detecting emitted or reflected energy. The energy may be nuclear, electromagnetic (including the visible and invisible portions of the spectrum), chemical, biological, thermal, or mechanical shoreline Intersection of the land with the water surface. slope map See: map, soil spheroid Mathematical figure closely approaching the geoid in form and size and used as a surface of reference for geodetic surveys. A reference spheroid or ellipsoid is a spheroid determined by revolving an ellipse about its shorter (polar) axis and used as a base for geodetic surveys of a large section of the Earth (such as the Clarke spheroid of 1866 which is used for geodetic surveys in the United States). spot elevation Point on a map or chart whose height above a specified datum is noted, usually by a dot or a small sawbuck and elevation value.

Elevations are shown, on a selective basis, for road forks and intersections, grade crossings summit of hills, mountain stadia Technique of distance measurement wherein the observer reads the intercept subtended on a graduated rod between two marks on the reticle of the telescope. standard-accuracy adjustment See: adjustment, standard-accuracy state plane coordinate system Coordinate systems established by the U.S. Coast and Geodetic Survey (now the National Ocean Survey), usually one for each state, for use in defining positions of points in terms of plane rectangular (x,y) coordinates. stereocompilation Production of a map or chart manuscript from aerial photographs and geodetic control data by means of photogrammetric instruments. stereoplotter Instrument for plotting a map by observation of stereomodels formed by pairs of photographs. stereoscopic Pertaining to the use of binocular vision for observation of a pair of overlapping photographs or other perspective views, giving impression of depth. storm evacuation map See: map, storm evacuation subsidence Decrease in the elevation of land surface due to tectonic, seismic, or artificial forces, without removal of surface material. survey Orderly process of determining data relating to any physical or chemical characteristics of the Earth.

The associated data obtained in a survey. An organization engaged in making a survey. tacheometer (tachymeter) Surveying instrument designed for use in the rapid determination of distance, direction, and difference of elevation from a single observation, using a short base which may be an intergraph part of the instrument. thematic map Precision surveying instrument for measuring horizontal and vertical angles. tide Periodic rise and fall of the water resulting from gravitational interactions between the Sun, Moon, and Earth. The vertical component of the particulate motion of a tidal wave. Although the accompanying horizontal movement of the water is part of the same phenomenon, it is preferable to designate this motion as tidal current. topographic map See: map, topographic topography Configuration (relief) of the land surface; the graphic delineation or portrayal of that configuration in map form, as by contour lines; in oceanography the term is applied to a surface such as the sea bottom or surface of given characteristics within the water mass. township Unit of survey of the public lands of the United States, normally a quadrangle approximately 6 miles on a side with boundaries conforming to meridians and parallels within established limits, containing 36 sections. Also, in minor governmental subdivision.

transit Precision surveying instrument; a theodolite in which the telescope can be reversed in direction by rotation about its horizontal axis. traverse Sequence of lengths and directions of lines connecting a series of stations, obtained from field measurements, and used in determining positions of the stations. triangulation Method of extending horizontal position on the surface of the Earth by measuring the angles of triangles and the included sides of selected triangles. trilateration Method of surveying wherein the lengths of the triangle sides are measured, usually by electronic methods, and the angles are computed from the measured lengths. Compare with triangulation. Universal Transverse Mercator (UTM) grid Military grid system based on the transverse Mercator projection, applied to maps of the Earth's surface extending from the Equator to 84 Degrees north and 80 degrees south latitudes upland Highland; ground elevation above the lowlands along rivers or between hills. zenith telescope Instrument for observing starts near the zenith (a point on the celestial sphere directly above the observer's position). ground below the water table where all the pores in rock, sediment, and soil are filled with water Isolines Here's a list of isolines you might discover as you explore geography ...

Contour line: Joins points of the same height above ground. Isobath: Joins points of the same depth below water. Isobar: Joins points with the same atmospheric pressure. Isotherm: Joins points with the same temperature. Isobathytherm: Joins points with the same temperature under water. Isocheim: Joins points with the same mean temperature in winter. Isothere: Joins points with the same mean summer temperature. Isogeotherm: Joins points with the same mean (average) temperature Isochrone: Joins points that it takes the same time to reach from a given place. Isodapane: Joins points where it costs the same to transport products from where they are made to where they are sold. Isotim: Joins points where it costs the same to transport a raw material from its source. Isohaline: Joins points where the salinity (amount of salt) of sea water is the same. Isohel: Joins points where the amount of sunshine is the same. Isohume: Joins points where the humidity (amount of water in the air) is the same.

Isyhyet: Joins points where the amount of precipitation (rainfall, snow etc) is the same. Isoneph: Joins points where the amount of cloud cover is the same. Isopectic: Joins places where ice begins to form at the same time each winter. Isotac: Joins points where ice begins to melt at the same time each spring. Isoplat: Joins places of equal acidity (used, for example, for mapping acid rain). Isopleth: Joins points of the same value (as a number), such as population or car ownership. Isopor: Joins points that have the same annual change in magnetic declination. Isostere: Joins points with the same atmospheric density. Isotach: Joins points with the same wind speed. Isogon: Joins points with the same wind direction. Isoshear: Joins points that experience the same wind shear. Isodrosotherm: Joins points of the same dewpoint temperature. Isoquant: Joints points of equal economic production. Isophene: Joints points where biological events happen at the same time, such as plants flowering or bulbs emerging.

Isodose: Joins points with the same radiation intensity. Isogloss: Joins points that share the same linguistic features. Isochalaz: Joins points with the same frequency of hail storms. Isobront: Joins points along the front of a storm. Isophote: Joins points with the same illuminance. Isochasm: Joins points with the same chance of an aurora occurring. High School Earth Science/Topographic Maps - Wikibooks, open books for an open world High School Earth Science/Topographic Maps From Wikibooks, open books for an open world This is the latest reviewed version , checked on 5 December 2015. There are 3 pending changes awaiting review. (+) Quality: minimal Explain what information a topographic map contains. Explain how to read and interpret a topographic map. Explain how various earth scientists use topographic maps to study the Earth. What is a Topographic Map?[ edit ] Mapping is a crucial part of earth science. Topographic maps represent the locations of major geological features. Topographic maps use a special type of line, called a contour line, to show different elevations on a map.

Contour lines are drawn on a topographic map to show the location of hills, mountains and valleys. When you use a regular road map, you can see where the roads go, but a road map doesn't tell you why a road stops or bends. A topographic map will show you that the road bends to go around a hill or stops because that is the top of a mountain. Let's look at topographic maps. Look at this view of Bryce Canyon National Park, Utah (Figure 2.26). You can see the rugged canyon walls and valley below. The terrain clearly has many steep cliffs. There are high and low points between the cliffs. Figure 2.26: View of Bryce Canyon National Park. Figure 2.27: Portion of Bryce Canyon National Park road map. Now look at the corresponding section of the Visitor's map (Figure 2.27). You can see a green line which is the main road. The black dotted lines are trails. You see some markers for campsites, a picnic area, and a shuttle bus stop. But nothing on the map shows the height of the terrain. Where are the hills and valleys located? How high are the canyon walls?

Which way will streams or rivers flow? You need a special type of map to represent the elevations in an area. This type of map is called a topographic map (Figure 2.28). What makes a topographic map different from other maps? Contour lines help show various elevations. Figure 2.28: Topographic map of Swamp Canyon Trail portion of Bryce Canyon National Park. Contour Lines and Intervals[ edit ] Contour lines connect all the points on the map that have the same elevation. Let's take a closer look at this (Figure 2.28). Each contour line represents a specific elevation and connects all the places that are at the same elevation. Every fifth contour line is in bold. The bold contour lines are labeled with numerical elevations. The contour lines run next to each other and NEVER cross one another. That would mean one place had two different elevations, which cannot happen. Two contour lines next to one another are separated by a constant difference in elevation (e.g. 20 ft or 100 ft.). This difference between contour lines is called the contour interval. You can calculate the contour interval. The legend on the map will also tell you the contour interval.

Take the difference in elevation between 2 bold lines. Divide that difference by the number of contour lines between them, PLUS 1. To put it another way: If the difference between two bold lines is 100 feet and there are four lines between them, what is the contour interval? If you answered 20 feet, then you are correct, 4+1=5, right? So, the calculation would be: (100 ft/5 = 20 ft). Interpreting Contour Maps[ edit ] How does a topographic map tell you about the terrain? Well, in reading a topographic map, consider the following principles: Contour lines can indicate the slope of the land. Closely-spaced contour lines indicate a steep slope, because elevation changes quickly in a small area. In contrast, broadly spaced contour lines indicate a shallow slope. Contour lines that seem to touch indicate a very steep or vertical rise, like a cliff or canyon wall. So, contour lines show the three-dimensional shape of the land. For example, on this topographic map of Stowe, Vermont (Figure 2.29), you will see a steep hill rising just to the right of the city of Stowe.

You can tell this because the contour lines there are closely spaced. Using the contour lines, you can see that the hill has a sharp rise of about 200 ft and then the slope becomes less steep as you proceed right. Figure 2.29: Portion of a USGS topographic map of Stowe, VT. In this map, you can see how the spacings of the contour lines indicate a steep hill just to the right of the city of Stowe in the right half. The hill becomes less steep as you proceed right. Concentric circles indicate a hill. Figure 2.30 shows another side of the topographic map of Stowe, Vermont. When contour lines form closed loops all together in the same area, this is a hill. The smallest loops are the higher elevations and the larger loops are downhill. If you look at the map, you can see Cady Hill in the lower left, and another smaller hill in the upper right. Figure 2.30: Portion of a USGS topographic map of Stowe, VT.

In this map, you can see Cady Hill (elevation 1122 ft) indicated by concentric circles in the lower left portion of the map and another hill (elevation ˜ 960 ft) in the upper right portion of the map. Hatched concentric circles indicate a depression. The hatch marks are short, perpendicular lines inside the circle. The innermost hatched circle would represent the deepest part of the depression, while the outer hatched circles represent higher elevations. V-shaped portions of contour lines indicate stream valleys. Here the V- shape of the contour lines “point” uphill. The channel of the stream passes through the point of the V and the open end of the V represents the downstream portion. Thus, the V points upstream. A blue line will indicate the stream if water is actually running through the valley; otherwise, the V patterns will indicate which way water will flow. Like other maps, topographic maps have a scale on them to tell you the horizontal distance. The horizontal scale helps to calculate the slope of the land (vertical height/horizontal distance).

Common scales used in United States Geological Service (USGS) maps include the following: 1:24,000 scale – 1 inch = 2000 ft 1:100,000 scale – 1 inch = 1.6 miles 1:250,000 scale – 1 inch = 4 miles So, the contour lines, their spacing intervals, circles, and V-shapes allow a topographic map to convert 3-dimensional information into a 2-dimensional representation on a piece of paper. The topographic map gives us an idea of the shape of the land. How Do Earth Scientists Use Topographic Maps?[ edit ] Figure 2.31: Bathymetric map of Bear lake, UT. Earth scientists use topographic maps for many things: Describing and locating surface features, especially geologic features. Determining the slope of the Earth's surface. Determining the direction of flow for surface water, ground water, and mudslides. Hikers, campers, and even soldiers use topographic maps to locate their positions in the field. Civil engineers use topographic maps to determine where roads, tunnels, and bridges should go.

Land use planners and architects also use topographic maps when planning development projects like housing projects, shopping malls, and roads. Oceanographers use a type of topographic map called a bathymetric map (Figure 2.31). In a bathymetric map, the contour lines represent depth from the surface. Therefore, high numbers are deeper depths and low numbers are shallow depths. Bathymetric maps are made from depth soundings or sonar data. Bathymetric maps help oceanographers visualize the bottoms of lakes, bays, and the ocean. This information also helps boaters to navigate safely. Geologic Maps[ edit ] A geologic map shows the geological features of a region. Rock units are shown in a color identified in a key. On the map of Yosemite, for example, volcanic rocks are brown, the Tuolumne Intrusive Suite is peach and the metamorphosed sedimentary rocks are green. Structural features, for example folds and faults, are also shown on a geologic map. The area around Mt. Dana on the east central side of the map has fault lines. Figure 2.32: Geologic map of the Yosemite area.

Figure 2.33: On a large scale geologic map, colors represent geological provinces. Lesson Summary[ edit ] Topographic maps are two-dimensional representations of the three-dimensional surface features of a given area. Topographic maps have contour lines which connect points of identical elevation above sea level. Contour lines run next to each other and adjacent contour lines are separated by a constant difference in elevation, usually noted on the map. Topographic maps have a horizontal scale to indicate horizontal distances. Topographic maps help users see how the land changes in elevation. Many people use topographic maps to locate surface features in a given area, to find their way through a particular area, and to determine the direction of water flow in a given area. Oceanographers use a special type of topographic map called a bathymetric map, which shows the bottom of any given body of water. Geologic maps display rock units and geologic features of a region of any size. A small scale map displays individual rock units while a large scale map shows geologic provinces. Review Questions[ edit ] On a topographic map, you see contour lines forming closed loops that all lie in the same area. Which of the following features would this indicate?

a stream channel depression a cliff Describe the pattern on a topographic map that would indicate a stream valley. How you would determine the direction of water flow? On a topographic map, five contour lines are very close together in one area. The contour interval is 100 ft. What feature does that indicate? How high is this feature? On a topographic map, how can you tell a steep slope from a shallow slope? On a topographic map, a river is shown crossing from Point A in the northwest to Point B in the southeast. Point A is on a contour line of 800 ft and Point B is on a contour line of 900 ft. In which direction does the river flow? What information would help you figure this out? On a topographic map, six contour lines span a horizontal distance of 0.5 inches. The horizontal scale is 1 inch equals 2000 ft. How far apart are the first and sixth lines? On a geologic map of the Grand Canyon, a rock unit called the Kaibab Limestone takes up the entire surface of the region.

Down some steep topographic lines is a very thin rock unit called the Toroweap Formation and just in from that is another thin unit, the Coconino sandstone. Describe how these three rock units sit relative to each other. A special type of map that show elevations of different geologic features of a region. Points to Consider[ edit ] Imagine that you are a civil engineer. Describe how you might use a topographic map to build a road, bridge, or tunnel through the area such as that shown in Figure 2.30. Would you want your road to go up and down or remain as flat as possible? What areas would need a bridge in order to cross them easily? Can you find a place where a tunnel would be helpful? If you wanted to participate in orienteering, would it be better to have a topographic map or a regular road map? How would a topographic map help you? If you were the captain of a very large boat, what type of map would you want to have to keep your boat traveling safely? Contour line - GIS Wiki | The GIS Encyclopedia Contour line Jump to: navigation , search This article is about lines of equal value in maps and diagrams.

For more meanings of the word "contour", see Contour . "Isopleth" and "Contour map" and "Contour interval" redirect here. A topographic map with relief shown by an elevation contour map A mathematical contour plot of the function f(x)=sin(x2+y2)cos(x)sin(y). Along the x-axis at -π/2 and π/2 it is constant zero, as it is on the y-axis at all integer multiples of π—hence the lines; the origin -centered circles are x2+y2 = π, x2+y2 = 2π ... A contour line (also level set, isopleth, isoline, isogram or isarithm) of a function of two variables is a curve along which the function has a constant value. [1] In cartography , a contour line (often just called a "contour") joins points of equal elevation (height) above a given level, such as mean sea level . [2] Contour lines are the means of relating the vertical dimension (the third dimension) of the topography of an area to the two-dimensional surface of a topographic map.

Contour lines should be visualized as the intersection of the land surface with a series of equally spaced, horizontal planes that pass through this surface. Contour or isarithmic maps connect regions of equal value using contours or isolines to illustrate a smooth, continuous phenomenon. A common contour map is a topographic map , which uses contour lines to show elevation, including steepness and slope. The contour interval of a topographic map is the difference in elevation between successive contour lines. [3] Contour or isarithmic maps can be used to show a variety of phenomena such as precipitation, temperature, atmospheric pressure, or solar radiation. Data used in isarithmic maps are not confined to predefined political or geographic boundaries. Rather, the data's parameters are as varied as its environment. The gradient of the function is always perpendicular to the contour lines. When the lines are close together the length of the gradient is large: the variation is steep. If adjacent contour lines are of the same line width, the direction of the gradient cannot be determined from the contour lines alone. However if contour lines rotate through three or more widths, or if the lines are numerically labelled, then the direction of the gradient can also be determined from the contour lines.

Contour lines are curved or straight lines on a map describing the intersection of a real or hypothetical surface with one or more horizontal planes. The configuration of these contours allows map readers to infer relative gradient of a parameter and estimate that parameter at specific places. Contour lines may be either traced on a visible three-dimensional model of the surface , as when a photogrammetrist viewing a stereo-model plots elevation contours, or interpolated from estimated surface elevations, as when a computer program threads contours through a network of observation points of area centroids. In the latter case, the method of interpolation affects the reliability of individual isolines and their portrayal of slope , pits and peaks. [4] Contents 8 References History The idea of lines that join points of equal value was rediscovered several times. In 1701, Edmond Halley used such lines (isogons) on a chart of magnetic variation.

[5] The Dutch engineer Nicholas Cruquius drew the bed of the river Merwede with lines of equal depth (isobaths) at intervals of 1 fathom in 1727, and Philippe Buache used them at 10-fathom intervals on a chart of the English Channel that was prepared in 1737 and published in 1752. The use of such lines to describe a land surface (contour lines) was studied theoretically by Ducarla in 1771, and Charles Hutton used them when calculating the volume of a hill in 1777. In 1791, a map of France by J. L. Dupain-Triel used contour lines at 20-metre intervals, hachures, spot-heights and a vertical section. In 1801, the chief of the Corps of Engineers, Haxo, used contour lines at the larger scale of 1:500 on a plan of his projects for Rocca d'Aufo.

[6] [7] [8] By around 1843, when the Ordnance Survey started to regularly record contour lines in Great Britain and Ireland, they were already in general use in European countries. Isobaths were not routinely used on nautical charts until those of Russia from 1834, and those of Britain from 1838. [9] [10] [6] When maps with contour lines became common, the idea spread to other applications. Perhaps the latest to develop are air quality and noise pollution contour maps, which first appeared in the USA, in approximately 1970, largely as a result of national legislation requiring spatial delineation of these parameters. In 2007, Pictometry was the first to allow users to dynamically generate elevation contour lines to be laid over oblique images. Types of contour lines Contour lines are often given specific names beginning "iso-" (from Greek ισος (isos), meaning 'equal') according to the nature of the variable being mapped, although in many usages the word "contour line" is most commonly used. Specific names are most common in meteorology, where multiple maps with different variables may be viewed simultaneously.

In general, an isoline is a line along which a variable is held constant. Meteorology Isohyetal map Meteorological contour lines are based on generalization from point data received from weather stations. Weather stations are seldom exactly positioned at a contour line (when they are, this indicates a measurement precisely equal to the value of the contour). Instead, lines are drawn to best approximate the locations of exact values based on the scattered information points available. Meteorological contour maps may present collected data such as actual air pressure at a given time, or generalized data such as average pressure over a period of time, or forecast data such as predicted air pressure at some point in the future Thermodynamic diagrams use multiple overlapping contour sets (including isobars and isotherms) to present a picture the major thermodynamic factors in a weather system. Barometric pressure Isobar map of Western Europe. Troughs are areas of greater variablility, signified by many isolines close together. Ridges are areas where there is little change in pressure over great distances. An isobar (from βαϝος or baros, meaning 'weight') is a line of equal or constant pressure on a graph, plot, or map; an isopleth or contour line of pressure.

More accurately, isobars are lines drawn on a map joining places of equal average atmospheric pressure reduced to sea level for a specified period of time. In meteorology, the barometric pressures shown are reduced to sea level , not the surface pressures at the map locations. The distribution of isobars is closely related to the magnitude and direction of the wind field, and can be used to predict future weather patterns. Isobars are commonly used in television news weather reporting, though more commonly in Europe than in the United States. An isostere is a line of constant atmospheric density. An isoheight or isohypse is a line of constant geopotential height on a constant pressure surface chart. Temperature and related subjects The 10°C mean isotherm in July, marked by the red line, is commonly used to define the Arctic region border An isotherm (from θεϝμη or thermē, meaning 'heat') is a line that connects points on a map that have the same temperature. Therefore, all points through which an isotherm passes have the same temperatures at the time indicated. Generally, isotherms representing 5°C or 10°F temperature differences are used, but any interval may be chosen.

An isogeotherm is a line of equal mean annual temperature. An isocheim is a line of equal mean winter temperature. An isothere is a line of equal mean summer temperature. An isohel (from έλιος or helios, meaning 'sun') is a line of equal or constant solar radiation. Precipitation and air moisture An isohyet or isohyetal line (from ϝετος or huetos, meaning 'rain') is a line joining points of equal precipitation on a map . A map with isohyets is called an isohyetal map. An isohume is a line of constant relative humidity. An isodrosotherm (from δϝοσος or drosos, meaning 'dew', and θεϝμη or therme, meaning 'heat') is a line of equal or constant dew point. An isoneph is a line indicating equal cloud cover. An isochalaz is a line of constant frequency of hail storms. An isobront is a line drawn through geographical points at which a given phase of thunderstorm activity occurred simultaneously. Snow cover is frequently shown as a contour-line map.

Wind An isotach (from ταχ or tach, meaning 'speed') is a line of constant wind speed. In general, an isogon is a line along which an angle is held constant. In meteorology, the term refers to a line of constant wind direction. Freeze and thaw An isopectic line denotes equal dates of ice formation each winter. An isotac denotes equal dates of thawing. Physical geography and Oceanography Elevation and depth Topographic map with isohypses of height Contours are one of several common methods used to denote elevation , altitude and depth on maps. From these contours, a sense of the general terrain can be determined. They are used on a variety of scales, from large-scale engineering drawings and architectural plans, through topographic maps up to continental-scale maps. A map showing the isobath lines of Bear Lake, Idaho, USA "Contour line" is the most common usage in cartography , but isobath for underwater depths on bathymetric maps and isohypse for elevations are also used. The process of drawing isohypse contour lines on a map is called isopletion.

In cartography, a contour interval is any space between contour lines, representing a difference in elevation between the lines. When calculated as a ratio against the map scale, a sense of the hilliness of the terrain can be derived. Magnetism In general, an isogon is a line along which an angle is held constant. In geomagnetism, the term refers to a line of constant magnetic declination (variance of magnetic north from geographic north). Isogonic lines are lines connecting those parts where the declination of the Earth's magnetic field is the same in amount. They are similar to isoclinic lines, which are lines connecting points of equal magnetic inclination. The line drawn through the points of zero magnetic declination is called the agonic line. Oceanography Besides ocean depth, oceanographers use contour to describe diffuse variable phenomena much as meteorologists do with atmospheric phenomena. isobathytherms are lines showing depths of water with equal temperature. isohalines show lines of equal ocean salinity. Isopycnals are surfaces of equal water density. Geology Various geological data are rendered as contour maps in structural geology, sedimentology, stratigraphy and economic geology.

Contour maps are used to show the below ground surface of geologic strata, fault surfaces (especially low angle thrust faults) and unconformities. Isopach maps use isopachs (lines of equal thickness) to illustrate variations in thickness of geologic units. Environmental science In discussing pollution, density maps can be very useful in indicating sources and areas of greatest contamination. Contour maps are especially useful for diffuse forms or scales of pollution. Acid precipitation is indicated on maps with isoplats. Some of the most widespread applications of environmental science contour maps involve mapping of environmental noise, air pollution, soil contamination, thermal pollution and groundwater contamination. Contour lines are being used by wildfire analysts to show temperature change in fire as it burns through different fuel types. This allows researchers to assess temperatures for optimum plant rejuvenation, which in turn allows land managers to assess the scale at which they can do ecological rehabilitation of certain areas. The cost of such projects is extensive and by knowing those areas which will rejuvenate themselves, managers can save money and focus on those areas where the fire had burned the hottest. Social sciences In economics, contour lines can be used to describe features which vary quantitatively over space.

An isochrone shows lines of equivalent drive time or travel time to a given location. An isotim shows equivalent transport costs from the source of a raw material, and an isodopane shows equivalent cost of travel time. Indifference curves are used to show bundles of goods to which a person would assign equal utility. In political science an analogous method is used in understanding coalitions (for example the diagram in Laver and Shepsle's work [12] ) In population dynamics, isocline refers to the set of population sizes at which the rate of change, or partial derivative, for one population in a pair of interacting populations is zero. Isolines can also be used to delineate qualitative differences. An isogloss, for example, is used in mapping the geographic spread of linguistic features. Contour lines are also used in non-geographic charts in economics. An isoquant is a line of equal production quantity, and an isocost shows equal production costs.

Thermodynamics, Engineering, and other sciences Various types of graphs in thermodynamics, engineering, and other sciences use isobars (for showing constant pressure), isotherms (for constant temperature), isochors (for constant specific volume), or other types of iso-lines (or curves), even though these graphs are usually not related to maps. Such iso-lines are useful for representing more than two dimensions (or quantities) on two-dimensional graphs. Common examples in thermodynamics are some types of phase diagrams. An Isocline is generically a line of equal slope. Isoclines are used to solve ordinary differential equations. In interpreting radar images: An isodop is a line of equal Doppler velocity. An isoecho is a line of equal radar reflectivity. Other phenomena isophene: biological events occurring with coincidence such as plants flowering isophote: illuminance Word List: Definitions of Contour Lines Tweets by @schrisomalis Contour Lines (Isolines) All right, you must think I'm off my rocker at last. Contour lines?

This list of 60 nouns beginning with "iso" defines words for contour lines on maps and diagrams that connect points having some feature (climatic, geographic, etc.) in common - also known as isolines or isograms. I wouldn't have thought there were so many of them before undertaking this site, but now that I've found them, I've become rather attached to them. So, now for my anecdote about isograms. When I was in high school (in south-central Ontario, Canada), my friends and I developed a particular isogram known as 'the stupid line'. This line demarcated the point north of which congenital idiots were found in great frequency (i.e. redneck country). The phrase 'north of the stupid line' came to signify an individual of subnormal intelligence and general social ignorance. So, what do you think of "isomoron"? Let me know.

Word line connecting points of equal deviation from mean temperature isacoustic line connecting points of equal acoustic quality isallobar line connecting points of equal change in barometric pressure iseidomal line connecting points of equal visibility of a spectacle isentropic line connecting points of equal entropy isobar line connecting points of same atmospheric pressure isobase line connecting points of equal land upheaval isobath line connecting points of equal underwater depth isobathytherm line connecting points of equal temperature and depth underground isobront line connecting points of simultaneous storm development isochar line connecting points of similar distinguishing characteristics of plant life isochasm line connecting points of equal frequency of aurorae isocheim line connecting points of same average winter temperature isochlor line connecting points of equal chlorine concentration isochor line connecting points of varying conditions under constant volume isochrone line connecting points of equal time difference or simultaneous occurrence isoclinal line connecting points of same magnetic dip isocryme line connecting points of equal winter temperature isodose line connecting points that receive equal doses of radiation isodrosotherm line connecting points of equal dew point isodynamic line connecting points of equal magnetic intensity isoflor line connecting points of equal number of plant species isogam line connecting points of equal acceleration

 due to gravity isogen line connecting points of equal birthrates isogeotherm line connecting points of equal subterranean temperature isogloss line connecting points of similar regional dialect isogon line connecting points of same specified angle or same wind direction isogonal line connecting points of equal magnetic declination isograd line connecting points of similar conditions during geological metamorphism isogram line connecting points on a map having some similar feature isograph line connecting points of same linguistic usage in some respect isohaline line connecting points of equal salinity isohalsine line connecting points of equal ocean salinity isohel line connecting points of equal sunlight isohyet line connecting points of equal rainfall isokeraunic line connecting points of equal occurrence of thunderstorms isolex line connecting points of same vocabulary usage isoline line connecting points on a map having some similar feature isomagnetic line connecting points of equal magnetic induction isometric line connecting points of equal variations of pressure isomorph line connecting points of same linguistic morphological forms isonephelic line connecting points of equal cloud cover isopach line connecting points of equal thickness of geological strata isophene line connecting points of the same phenotype or seasonal variation isophote line connecting points of equal light intensity from a given source isopi

estic line connecting points of equal pressure but varying temperature and volume isopiptesis line connecting points of same arrival date of migratory species isopleth line connecting points of equal aspect of climate isopor line connecting points of equal annual change in magnetic field isopycnic line connecting points of equal density isorithm line connecting points of equal population density isoseismal line connecting points of same earthquake intensity isostere line connecting points of equal specific volume of a substance isotac line joining points where the ice melts at the same time of year isotach line connecting points of the same wind speed isothere line connecting points of equal summer temperature isotherm line connecting points of equal temperature isothermobath line connecting points of equal temperature at a given ocean depth isotherombrose What Are Isolines What Are Isolines By Matt Rosenberg Updated August 02, 2016.

Topographic maps use a wide variety of symbols to represent human and physical features, including isolines, which are often used on maps to represent points of equal value. Isolines, also referred to as contour lines, can be used to represent elevation on a map by connecting points of equal elevation, for instance. These imaginary lines provide a good visual representation of the terrain. As with all isolines, when contour lines lie close together, they represent a steep slope; lines far apart represent a gradual slope. But isolines can also be used to show other variables on a map besides terrain, and in other themes of study. For example, the first map of Paris used isolines to depict population distribution in that city, rather than physical geography. Maps using isolines and their variations have been used by astronomer Edmond Halley (of Halley's comet) and by doctor John Snow to better understand an 1854 cholera epidemic in England. This is a list of some common (as well as obscure) types of isolines used on maps to represent different features of terrain, such as elevation and atmosphere, distances, magnetism and other visual representations not easily shown on a two-dimensional depiction.

The prefix "iso-" means "equal." Isobar A line representing points of equal atmospheric pressure. Isobath A line representing points of equal depth under water. Isobathytherm A line representing depths of water with equal temperature. Isochasm A line representing points of equal recurrence of auroras. Isocheim A line representing points of equal mean winter temperature. Isochrone A line representing points of equal time-distance from a point, such as the transportation time from a particular point. Isodapane A line representing points of equal transport costs for products from production to markets. Isodose A line representing points of equal intensity of radiation. Isodrosotherm A line representing points of equal dew point. Isogeotherm A line representing points of equal mean temperature. Isogloss A line separating linguistic features. Isogonal A line representing points of equal magnetic declination. Isohaline A line representing points of equal salinity in the ocean. Isohel A line representing points receiving equal amounts of sunshine. Isohume A line representing points of equal humidity. Isohyet A line representing points of equal precipitation. Isoneph A line representing points of equal amounts of cloud cover.

Isopectic A line representing points where ice begins to form at the same time each fall or winter. Isophene A line representing points where biological events occur at the same time, such as crops flowering. Isoplat A line representing points of equal acidity, as in acid precipitation. Isopleth A line representing points of equal numerical value, such as population. Isopor A line representing points of equal annual change in magnetic declination. Isostere A line representing points of equal atmospheric density. Isotac A line representing points where ice begins to melt at the same time each spring. Isotach A line representing points of equal wind speed. Isothere A line representing points of equal mean summer temperature. Isotherm A line representing points of equal temperature. Isotim An "iso-" word for a contour line that connects points of equal elevation - English Language & Usage Stack Exchange Can you give a cite? – bib Mar 5 '14 at 21:39 And yes, @WS2, "isohypse" itself is esoteric, hence its absence from maps published by the Ordnance Survey, the U.S. Geological Survey, and nearly every other publisher of contour maps.

I was several years into postgraduate work in geography before I encountered it, pursuing the same line of thought expressed in the original question. – Joan Pederson Mar 5 '14 at 21:40 (1) I do not have handy access to the AHDEL, 4e, but if you search for "isohypse" on ahdictionary.com, it says "No word definition found". (2) Same when I searched on the GIS Dictionary - "Sorry, isohypse was not found." (support.esri.com/en/knowledgebase/Gisdictionary/browse) (3) Nowhere does the word "isohypse" appear in the lattermost article you cite (Patterson and Jenny, 2011). – Kenny LJ Mar 5 '14 at 22:22 Wikipedia (OP's reference) has: "Contour line" is the most common usage in cartography, but isobath for underwater depths on bathymetric maps and isohypse for elevations are also used.

– Edwin Ashworth Mar 5 '14 at 22:58 There are a few English texts in Google Books clearly using isohypse to mean a line connecting points of equal elevation. But the vast majority of indexed entries seem to be in German or French. Also note this text , saying isohypse ... line drawn on a map to join places where the thickness of a given atmospheric layer is the same. It's not really worth OP taking this one on board. He'd do better to alter his mistaken opinion on what "contour line" means. – FumbleFingers Mar 5 '14 at 23:50

Question: On a map, what name is given to a line linking places in the sea that are of equal depth?
Answer: ISOBATH