Science

Types of Map Legend Symbol

Name: Types of Map Legend Symbol
Creator: Community curated
License: https://creativecommons.org/licenses/by/4.0/

Scale bars, compass roses, contour lines — which cartographic symbol is the most essential for reading a map?

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Source:Community curated

Updated:3/7/2026

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Symbol↕	Category↕	Usage↕	Origin / Era↕	Known For↕
Compass Rose	Orientation	Shows cardinal and intercardinal directions	13th-century portolan charts	32-point wind rose on nautical charts, decorative centerpiece of Renaissance maps, essential for navigation
Scale Bar	Measurement	Visual representation of map-to-ground distance	16th-century cartography	Survives resizing unlike ratio scales (1:50,000), essential for distance estimation, dual metric/imperial bars
Contour Lines	Topography	Connect points of equal elevation	Charles Hutton, 1774	Closer lines = steeper terrain, index contours every 5th line, backbone of topographic maps worldwide
North Arrow	Orientation	Indicates true north or grid north	Medieval mappamundi	Simplest orientation symbol, distinguishes true north from magnetic north, mandatory on engineering drawings
Grid Reference System	Location	Alphanumeric coordinates for locating features	Military grid reference (WWI era)	NATO MGRS system, OS grid references in UK, 6-figure references pinpoint to 100m, essential for search & rescue
Hachures	Topography	Short lines showing slope direction and steepness	Johann Georg Lehmann, 1799	Pre-contour method of showing relief, thicker/closer = steeper, still used on some military maps
Legend/Key Box	Reference	Explains all symbols used on the map	Ancient cartography	The decoder ring for every map, groups symbols by category, must be complete and unambiguous
Spot Height	Topography	Exact elevation at a specific point	Triangulation surveys, 18th century	Dot with number showing precise altitude, marks summits and passes, supplements contour lines with exact data
Isobath (Depth Contour)	Hydrography	Lines of equal water depth on nautical charts	Early hydrographic surveys	Blue-tinted depth zones on nautical charts, critical for ship navigation, measured from chart datum (lowest tide)
Choropleth Shading	Thematic	Color-coded areas showing statistical data density	Charles Dupin, 1826 (first known)	Election maps, population density maps, can be misleading (large empty areas dominate visually)
Proportional Symbol	Thematic	Circles/squares sized by data value at point locations	19th-century statistical cartography	Bubble maps showing city population, earthquake magnitude, avoids choropleth's area bias problem
Flow Line / Arrow	Thematic	Shows direction and volume of movement	Charles Minard's maps, 1860s	Minard's Napoleon march map called 'best statistical graphic ever drawn', trade routes, migration paths
Benchmark (BM)	Survey	Permanent surveyed elevation point	Ordnance Survey, 1840s	Cut mark on buildings/pillars showing exact surveyed height, 'benchmark' entered everyday language from this
Cartouche	Decorative	Ornamental frame containing map title and info	16th-century European maps	Elaborate baroque frames with mythological figures, publisher info, dedication to patron, highly collectible art
Relief Shading (Hillshade)	Topography	3D shadow effect showing terrain shape	Eduard Imhof, mid-20th century	NW illumination convention, makes mountains 'pop' off the page, Swiss cartographic tradition, now auto-generated from DEM

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