Science

Types of Map Legend Symbol

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Updated:3/7/2026
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Symbol
Category
Usage
Origin / Era
Known For
Compass Rose
OrientationShows cardinal and intercardinal directions13th-century portolan charts32-point wind rose on nautical charts, decorative centerpiece of Renaissance maps, essential for navigation
Scale Bar
MeasurementVisual representation of map-to-ground distance16th-century cartographySurvives resizing unlike ratio scales (1:50,000), essential for distance estimation, dual metric/imperial bars
Contour Lines
TopographyConnect points of equal elevationCharles Hutton, 1774Closer lines = steeper terrain, index contours every 5th line, backbone of topographic maps worldwide
North Arrow
OrientationIndicates true north or grid northMedieval mappamundiSimplest orientation symbol, distinguishes true north from magnetic north, mandatory on engineering drawings
Grid Reference System
LocationAlphanumeric coordinates for locating featuresMilitary grid reference (WWI era)NATO MGRS system, OS grid references in UK, 6-figure references pinpoint to 100m, essential for search & rescue
Hachures
TopographyShort lines showing slope direction and steepnessJohann Georg Lehmann, 1799Pre-contour method of showing relief, thicker/closer = steeper, still used on some military maps
Legend/Key Box
ReferenceExplains all symbols used on the mapAncient cartographyThe decoder ring for every map, groups symbols by category, must be complete and unambiguous
Spot Height
TopographyExact elevation at a specific pointTriangulation surveys, 18th centuryDot with number showing precise altitude, marks summits and passes, supplements contour lines with exact data
Isobath (Depth Contour)
HydrographyLines of equal water depth on nautical chartsEarly hydrographic surveysBlue-tinted depth zones on nautical charts, critical for ship navigation, measured from chart datum (lowest tide)
Choropleth Shading
ThematicColor-coded areas showing statistical data densityCharles Dupin, 1826 (first known)Election maps, population density maps, can be misleading (large empty areas dominate visually)
Proportional Symbol
ThematicCircles/squares sized by data value at point locations19th-century statistical cartographyBubble maps showing city population, earthquake magnitude, avoids choropleth's area bias problem
Flow Line / Arrow
ThematicShows direction and volume of movementCharles Minard's maps, 1860sMinard's Napoleon march map called 'best statistical graphic ever drawn', trade routes, migration paths
Benchmark (BM)
SurveyPermanent surveyed elevation pointOrdnance Survey, 1840sCut mark on buildings/pillars showing exact surveyed height, 'benchmark' entered everyday language from this
Cartouche
DecorativeOrnamental frame containing map title and info16th-century European mapsElaborate baroque frames with mythological figures, publisher info, dedication to patron, highly collectible art
Relief Shading (Hillshade)
Topography3D shadow effect showing terrain shapeEduard Imhof, mid-20th centuryNW illumination convention, makes mountains 'pop' off the page, Swiss cartographic tradition, now auto-generated from DEM

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