Types of Map Legend Symbol
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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