Cartography tricks that make maps readable

Latitude = horizontal lines (N/S). Longitude = vertical lines (E/W). latLITude lies flat.

Coordinates — Latitude: horizontal lines, measure N/S of equator (0–90°). Longitude: vertical lines, measure E/W of prime meridian (0–180°). GPS coordinates: latitude listed first.

Mercator distorts area: Greenland looks Africa-sized. Peters preserves area.

Map Projections — Mercator (cylindrical): preserves shape and direction but inflates area at poles. Peters (equal-area): correct area but distorted shape. No projection is perfect. All are compromises.

Map scale 1:24,000 = 1 unit on map = 24,000 units in reality

Map Scale — 1 inch on a 1:24,000 map = 24,000 inches = 2,000 feet in reality. Larger scale number = smaller area, more detail (1:10,000). Smaller scale number = larger area, less detail (1:1,000,000).

Contour lines: close together = steep. V pointing uphill = valley.

Topographic Maps — Each contour line connects points of equal elevation. Close lines: steep slope. Wide lines: gentle slope. V-shapes pointing uphill = valley/stream. V-shapes pointing downhill = ridge.

GIS (Geographic Information System) — layers of spatial data for analysis

GIS — GIS combines multiple data layers (terrain, population, land use, roads) for analysis. Used in urban planning, disaster response, epidemiology, environmental science. Google Maps is a simplified consumer version.

Remote sensing: satellites and aircraft collect data about Earth's surface without direct contact

Remote Sensing — Passive sensors: detect natural energy reflected or emitted from Earth (visible light, infrared, thermal). Active sensors: emit energy and measure what bounces back (radar, LiDAR). Applications: land use mapping, crop monitoring, disaster assessment, military surveillance, climate monitoring. Google Earth uses remote sensing imagery.

Prime meridian: 0° longitude through Greenwich, England. International Date Line: ~180° longitude.

Prime Meridian and Date Line — Prime meridian (0°): established 1884 at Royal Observatory, Greenwich. All longitude measured east or west of it. International Date Line (~180°): where the calendar changes. Cross going west: gain a day. Cross going east: lose a day. Zigzags to avoid splitting countries (Kiribati, Fiji).

Choropleth map: shades regions by value. Dot map: each dot = a quantity. Proportional symbol: size = value.

ChoroplethShaded regions by value

Dot mapEach dot = a quantity

Proportional symbolSymbol size = value

IsolineLines of equal value

GPS (Global Positioning System): 24 plus satellites triangulate position to within meters.

GPS Technology — GPS: US Department of Defense system, 24+ satellites in medium Earth orbit. Receiver needs signals from at least 4 satellites to calculate 3D position (latitude, longitude, altitude). Accuracy: civilian 3-5 meters, military better. GLONASS (Russia), Galileo (EU), BeiDou (China): other GNSS systems.

Mental maps: internal geographic representations. Vary by individual, culture, and experience.

Mental Maps — Mental maps (cognitive maps): internalized, subjective representations of geographic space. Shaped by personal experience, media, education. Distance decay: knowledge decreases with distance from home. Upward distortion: home region often drawn larger than actual size. Stereotyping: regions reduced to simplified images.

Gerrymandering: manipulating district boundaries for political advantage — geography used as a weapon

Gerrymandering and Electoral Geography — Named after Elbridge Gerry (Massachusetts governor, 1812). Packing: concentrate opposition voters in a few districts — they win big there, wasted votes elsewhere. Cracking: split opposition voters across many districts — they lose everywhere. Modern gerrymandering uses sophisticated algorithms. Supreme Court: political gerrymandering is a political question, not justiciable.

Spatial analysis: asking geographic questions — where is it, why is it there, what patterns exist?

Spatial Analysis — Geography asks spatial questions: location, distribution, pattern, association, interaction, change. Spatial autocorrelation: nearby things tend to be more similar than distant things (Tobler's First Law). Cluster analysis: identifying geographic concentrations. Buffer analysis: areas within a given distance. Overlay: combining multiple data layers.