1Map projections and coordinate systems.pptx - MAP PROJECTIONS AND COORDINATE SYSTEMS MAP PROJECTIONS AND COORDINATE SYSTEMS \u2022 DEFINING COORDINATES

1Map projections and coordinate systems.pptx - MAP...

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MAP PROJECTIONS AND COORDINATE SYSTEMS
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MAP PROJECTIONS AND COORDINATE SYSTEMS DEFINING COORDINATES FOR THE EARTH’S SURFACE IS COMPLICATED: MOST PEOPLE BEST UNDERSTAND GEOGRAPHY IN A COORDINATE SYSTEM ON A FLAT SURFACE. HUMANS PERCEIVE THAT THE WORLD IS FLAT. WE CAN’T SEE THE CURVE. A FLAT MAP DISTORTS THE GEOMETRY BECAUSE THE EARTH IS CURVED. WE NEED TO USE A MAP PROJECTION IF WE WANT TO REPRESENT THE EARTH’S CURVED SURFACE ON A FLAT SURFACE THE EARTH DOES NOT HAVE A REGULAR SHAPE. WE LEARN THAT IT IS A SPHERE, BUT THIS IS JUST AN APPROXIMATION. OUR MEASUREMENTS ARE NOT PERFECT, BOTH OF THE SHAPE OF THE EARTH AND OUR MEASUREMENTS OF POSITIONS ON THE EARTH
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VOCABULARY DISTORTION: TO CHANGE THE PHYSICAL SHAPE OF SOMETHING PARALLELS: LINES OF LATITUDE. MEASURED IN A NORTH/SOUTH DIRECTION. MERIDIANS: LINES OF LONGITUDE. MEASURED IN A EAST/WEST DIRECTION. SPHEROID/ELLIPSOID : AN IMPERFECT SPHERE (OVAL). MAP SCALE : THE RATIO OF THE MAP DISTANCE TO THE CORRESPONDING DISTANCE ON THE GROUND. EXAMPLE: A 1:24,000 SCALE MAP CAN MEAN: 1 CM ON A MAP = 240 METERS ON THE GROUND OR 1 INCH ON A MAP = 24,0000 IN. (2,000 FT) ON THE GROUND LARGE (FINE) VS SMALL (COARSE) SCALE : LARGE SCALE MAPS SHOW MORE DETAIL IN A SMALLER AREA THAN SMALL SCALE MAPS. MAP SCALES OF 1:24,000 OR LARGER (E.G.1:10,000; 1:5:000) ARE CONSIDERED LARGE SCALE.
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VOCABULARY GEOGRAPHIC COORDINATES: LONGITUDE AND LATITUDE PROJECTION: CONVERTS DATA SETS FROM GEOGRAPHIC COORDINATES TO PROJECTED COORDINATES. DEGREES-MINUTES-SECONDS (DMS): ANGULAR MEASURING SYSTEM THAT IS USED TO MEASURE LATITUDE AND LONGITUDE. DECIMAL DEGREES : OFTEN USED IN GIS. TO CONVERT FROM DMS, DIVIDE MINUTES BY 60 AND SECONDS BY 3600.
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ACCURACY AND PRECISION Low Accuracy High Precision High Accuracy Low Precision High Accuracy High Precision Accuracy : The ability of a measurement to describe a landscape feature's true location, size, or condition. Nearness of a calculation to its true value. Precision : The relative consistency among a set of measurements. In other words, how close the measured values are to each other.
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BASIC PRINCIPLES THE EARTH IS A SPHEROID (MANY DIFFERENT SPHEROIDS USED TO DEFINE THE EARTH’S SHAPE) NOT A PERFECT SPHEROID OR SPHERE, BUT SLIGHTLY FLATTENED AT THE POLES AND BULGES AT THE EQUATOR (CAUSED BY DIFFERENCES IN DENSITY OF THE EARTH). A SPHEROID IS CHOSEN TO FIT ONE COUNTRY OR A PARTICULAR AREA. WHAT FITS ONE PLACE MAY NOT FIT ANOTHER. A GEOGRAPHIC COORDINATE SYSTEM IS THE REFERENCE SYSTEM FOR LOCATING SPATIAL FEATURES ON THE EARTH’S SURFACE COORDINATES ARE LAID OUT ON A GRID LATITUDE (PARALLELS/Y) AND LONGITUDE (MERIDIANS/X)
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GEOGRAPHIC COORDINATES LATITUDE (Y) THE ANGLE FROM THE EQUATOR TO A SET LOCATION IN A NORTH/SOUTH DIRECTION REPRESENTED BY HORIZONTAL LINES 0-90 DEGREES NORTH AND SOUTH OF THE EQUATOR LONGITUDE (X) THE ANGLE FROM THE PRIME MERIDIAN TO A SET LOCATION IN AN EAST/WEST DIRECTION REPRESENTED BY VERTICAL LINES
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  • Fall '19
  • Geography, Map projection, map projections

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