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Map Projections

Map Projections. The Earth is a spheroid. A mathematical conversion must be used to create a flat map sheet from the three-dimensional surface. The Earth needs to be transformed. Projection is a mathematical procedure of representing the globe on a flat surface.

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Map Projections

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  1. Map Projections

  2. The Earth is a spheroid A mathematical conversion must be used to create a flat map sheet from the three-dimensional surface. The Earth needs to be transformed.

  3. Projection is a mathematical procedure of representing the globe on a flat surface.

  4. How do you put a round surface on a flat paper ? • Mathematically, a projection is a process of transforming global location to a planar position. • Planar coordinate systems: • Have two dimensions, • X measures distance in a horizontal direction • Y measures distance in a vertical direction • Measures of length, angle, and area are constant across the dimension

  5. UTM = Universe Transverse Mercator WGS = World Geodetic System NAD = North American Datum GRS = Geodetic Reference System Oblate Ellipsoid or Spheroid Different Acronyms

  6. 1924 measurements were: e = 6,378,206.4 P = 6,356,538.8 m Or: f = 1/297 1980 (GRC80) Geodetic Reference System 1983 (NAD83) WGS84 World Geodetic System F = 1/300 The Earth is not a ball e p F = 1-p/e NAD1927 (North American Datum)

  7. Any representation of the earth’s surface in two dimensions: • Causes some distortion: • 4 types of distortion: • Shape • area • distance • direction • Different projections produce different distortions

  8. Some commonly used map projections in the U.S. and North America

  9. UTM a Planar Coordinate System

  10. Latitude and Longitude Is a geographic referencing system NOT a projection

  11. UTM Zone 13

  12. Lambert Conformal Conic

  13. Albers Equal-Area Conic

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