Class 3a: The Round Earth, or Map Projections and Climate BasicsHow hot is it?InsolationWhat causes the seasons?Latitude and longitudeSlide 6Map projectionsSlide 8Cylindrical projectionsCylindrical projections: Gall- PetersConic projectionsPlanar projectionsOther projectionsClass 3a: The Round Earth, orMap Projections and Climate BasicsHow hot is it?•What determines temperature?•Insolation (incoming s olar radiation)•Cloud cover•Altitude•Water vapor in the air•Land or water•Air movement (wind)Insolation•Only at one latitude at a time are the sun’s rays overhead–Between Tropic of Cancer and Tropic of Capricorn•Everywhere else, rays are diffusedWhat causes the seasons?•Volunteers?•The tilt of the earth•The angle of sunlight•The change in heat received from the sunLatitude and longitude•Latitude: how far north or south•From 0° at equator to 90° at poles•Each parallel of latitude is a different size•Key latitudes: Equator, 23.5°N and SLatitude and longitude•Longitude: how far east or west•East or west of what?•1884 agreement on prime meridian at Greenwich•Each meridian of longitude is the same distance around•Not parallel lines•Key longitudes: Prime Meridian, International Date Line, 100th meridianMap projections•Project a round globe onto a flat surface•Options?•Stretch out some areas•Cut out some areas•Shrink some areasMap projections•Three properties to consider–Area (equal-area or equivalent)–Shape (conformal)–Distance (equidistant)–Choose two out of three•How large an area?•Purpose of the map•Ulterior motives?Cylindrical projections•Shapes are preserved•But not area!•Mercator projection•Deliberate distortion?–Cold War–ColonialismCylindrical projections: Gall- Peters•Adjusting Mercator for a more “just” map •Also preserves area•Distorts shape differentlyConic projections•Best for hemispheres or small regions•Area and shape only slightly distortedPlanar projections•Equidistant; good for navigation•Only good for one hemisphere•Distorts area, not shapeOther projections•Based on more complicated math•Interrupted, oval,
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