Understanding Map Projections

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MERCATOR Greenland is only one-eighth the size of South America, Greenland appears to be larger. Direction Any straight line drawn on this projection represents an actual compass bearing. These true direction lines are rhumb lines and generally do not describe the shortest distance between points. Distance Scale is true along the equator or along the secant latitudes. The central meridian is 0°. DESCRIPTION Originally created to display accurate compass bearings for sea travel. An additional feature of this projection is that all local shapes are accurate and clearly defined. PROJECTION METHOD Cylindrical projection. Meridians are parallel to each other and equally spaced. The lines of latitude are also parallel but become farther apart toward the poles. The poles cannot be shown. LINES OF CONTACT The equator or two latitudes symmetrical around the equator. LIMITATIONS The poles cannot be represented on the Mercator projection. All meridians can be projected, but the upper and lower limits of latitude are approximately 80° N and S. Large area distortion makes the Mercator projection unsuitable for general geographic world maps. USES AND APPLICATIONS Standard sea navigation charts (direction). Other directional uses: air travel, wind direction, ocean currents. Conformal world maps. The best use of this projection’s conformal properties applies to regions near the equator such as Indonesia and parts of the Pacific Ocean. LINEAR GRATICULES All meridians and all parallels. PROPERTIES Shape Conformal. Small shapes are well represented because this projection maintains the local angular relationships. Area Increasingly distorted toward the polar regions. For example, in the Mercator projection, although 70 • Understanding Map Projections
MILLER CYLINDRICAL Direction Local angles are correct only along the equator. Distance Correct distance is measured along the equator. LIMITATIONS Useful only as a world map. USES AND APPLICATIONS General-purpose world maps. The central meridian is 118° W. DESCRIPTION This projection is similar to the Mercator projection except that the polar regions are not as areally distorted. Spacing between lines of latitude as they approach the poles is less than in the Mercator projection. It decreases the distortion in area, but the compromise introduces distortion in local shape and direction. PROJECTION METHOD Cylindrical projection. Meridians are parallel and equally spaced, lines of latitude are parallel, and the distance between them increases toward the poles. Both poles are represented as straight lines. LINE OF CONTACT The equator. LINEAR GRATICULES All meridians and all parallels. PROPERTIES Shape Minimally distorted between 45th parallels, increasingly toward the poles. Land masses are stretched more east–west than they are north–south. Area Distortion increases from the equator toward the poles. Supported map projections• 71
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Understanding Map Projections GIS b
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Contents CHAPTER 1: GEOGRAPHIC COOR
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State Plane Coordinate System .....
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GEOGRAPHIC COORDINATE SYSTEMS A geo
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SPHEROIDS AND SPHERES The shape and
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DATUMS While a spheroid approximate
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2 Projected coordinate systems Proj
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WHAT IS A MAP PROJECTION? Whether y
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PROJECTION TYPES Because maps are f
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maintained for both small-scale and
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Planar projections Planar projectio
Page 25 and 26: OTHER PROJECTIONS The projections d
Page 27: The four parameters above are used
Page 30 and 31: GEOGRAPHIC TRANSFORMATION METHODS M
Page 32 and 33: Unless explicitly stated, it’s im
Page 34 and 35: National Transformation version 2 L
Page 36 and 37: LIST OF SUPPORTED MAP PROJECTIONS A
Page 38 and 39: Loximuthal McBryde-Thomas Flat-Pola
Page 40 and 41: AITOFF USES AND APPLICATIONS Develo
Page 42 and 43: ALASKA SERIES E LIMITATIONS This pr
Page 44 and 45: AZIMUTHAL EQUIDISTANT Area Distorti
Page 46 and 47: BIPOLAR OBLIQUE CONFORMAL CONIC DES
Page 48 and 49: CASSINI-SOLDNER Area No distortion
Page 50 and 51: CRASTER PARABOLIC Distance Scale is
Page 52 and 53: DOUBLE STEREOGRAPHIC Oblique aspect
Page 54 and 55: ECKERT II The central meridian is 1
Page 56 and 57: ECKERT IV parallels. Nearer the pol
Page 58 and 59: ECKERT VI central meridian. Scale i
Page 60 and 61: EQUIDISTANT CYLINDRICAL LINES OF CO
Page 62 and 63: GALL’S STEREOGRAPHIC Area Area is
Page 64 and 65: GEOCENTRIC COORDINATE SYSTEM Geogra
Page 66 and 67: GNOMONIC PROPERTIES Shape Increasin
Page 68 and 69: HAMMER-AITOFF LIMITATIONS Useful on
Page 70 and 71: KROVAK Direction Local angles are a
Page 72 and 73: LAMBERT CONFORMAL CONIC Area Minima
Page 74 and 75: LOXIMUTHAL Distance Scale is true a
Page 78 and 79: MOLLWEIDE Distance Scale is true al
Page 80 and 81: ORTHOGRAPHIC PROPERTIES Shape Minim
Page 82 and 83: PLATE CARRÉE Direction North, sout
Page 84 and 85: POLYCONIC Direction Local angles ar
Page 86 and 87: RECTIFIED SKEWED ORTHOMORPHIC DESCR
Page 88 and 89: SIMPLE CONIC Equirectangular projec
Page 90 and 91: SPACE OBLIQUE MERCATOR DESCRIPTION
Page 92 and 93: Montana—The three zones for Monta
Page 94 and 95: TIMES LIMITATIONS Useful only for w
Page 96 and 97: 10,000,000 meters to ensure that al
Page 98 and 99: UNIVERSAL POLAR STEREOGRAPHIC Area
Page 100 and 101: VAN DER GRINTEN I Distance Scale al
Page 102 and 103: WINKEL I Distance Generally, scale
Page 104 and 105: WINKEL T RIPEL Distance Generally,
Page 107 and 108: Glossary angular units The unit of
Page 109 and 110: High Accuracy Reference Network A r
Page 111: UTM See Universal Transverse Mercat
Page 114 and 115: Eckert VI 52 ED 1950 6 Ellipse 101
Page 116: Projections (continued) planar 17,
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Understanding Map Projections

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