Understanding Map Projections

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AITOFF USES AND APPLICATIONS Developed for use in general world maps. Used for the Winkel Tripel projection. The central meridian is 0°. DESCRIPTION A compromise projection developed in 1889 and for use with world maps. PROJECTION METHOD Modified azimuthal. Meridians are equally spaced and concave toward the central meridian. The central meridian is a straight line and half the length of the equator. Parallels are equally spaced curves, concave toward the poles. LINEAR GRATICULES The equator and the central meridian. PROPERTIES Shape Distortion is moderate. Area Moderate distortion. Direction Generally distorted. Distance The equator and central meridian are at true scale. LIMITATIONS Neither conformal nor equal area. Useful only for world maps. 34 • Understanding Map Projections
ALASKA GRID Distance The minimum scale factor is 0.997 at approximately 62°30' N, 156° W. Scale increases outward from this point. Most of Alaska and the Aleutian Islands, excluding the panhandle, are bounded by a line of true scale. The scale factor ranges from 0.997 to 1.003 for Alaska, which is one-fourth the range for a corresponding conic projection (Snyder, 1987). LIMITATIONS Distortion becomes severe away from Alaska. Parameters are set by the software. DESCRIPTION This projection was developed to provide a conformal map of Alaska with less scale distortion than other conformal projections. A set of mathematical formulas defines a conformal transformation between two surfaces (Snyder, 1993). USES AND APPLICATIONS Conformal mapping of Alaska as a complete state on the Clarke 1866 spheroid or NAD27. This projection is not optimized for use with other datums and spheroids. PROJECTION METHOD Modified planar. This is a sixth-order equation modification of an oblique Stereographic conformal projection on the Clarke 1866 spheroid. The origin is at 64° N, 152° W. POINT OF TANGENCY Conceptual point of tangency at 64° N, 152° W. LINEAR GRATICULES None. PROPERTIES Shape Perfectly conformal. Area Varies about 1.2 percent over Alaska. Direction Local angles are correct everywhere. Supported map projections• 35
Page 1 and 2: Understanding Map Projections GIS b
Page 3 and 4: Contents CHAPTER 1: GEOGRAPHIC COOR
Page 5: State Plane Coordinate System .....
Page 8 and 9: GEOGRAPHIC COORDINATE SYSTEMS A geo
Page 10 and 11: SPHEROIDS AND SPHERES The shape and
Page 12 and 13: DATUMS While a spheroid approximate
Page 15 and 16: 2 Projected coordinate systems Proj
Page 17 and 18: WHAT IS A MAP PROJECTION? Whether y
Page 19 and 20: PROJECTION TYPES Because maps are f
Page 21 and 22: maintained for both small-scale and
Page 23 and 24: 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 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 76 and 77: MERCATOR Greenland is only one-eigh
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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