UNIT 27 - MAP PROJECTIONS

UNIT 27 - MAP PROJECTIONS

Compiled with assistance from Vicki Chmill, University of California, Santa Barbara


For Information that Supplements the Contents of this Unit:

Coordinates: Cylindrical, Spherical and Polar -- Illustrated and described; plus conversion formulae.
Errors in Maps (Chrisman/U of Washington) -- US data quality standards.
Error, Accuracy and Precision (Geographer's Craft) -- (A few graphics); types of errors; sources of inaccuracy and imprecision; problems of propagation and cascading; beware of false precision and false accuracy; dangers of undocumented data; principles of managing error.
Map Projection Overview (Dana/Geographer's Craft) -- Illustrated and described selected map projections: Cylindrical (Behrmann Equal Area, Mercator); Pseudocylindrical (Mollweide, Sinusoidal); Conic (Albers Equal Area, Stereographic); Azimuthal (Orthographic, Stereographic); etc.
Modified UTM Grid Projections -- Article on applications for field and computer generated coordinate systems (McDowell).


  • A. INTRODUCTION
  • B. DISTORTION PROPERTIES
  • C. FIGURE OF THE EARTH
  • D. GEOMETRIC ANALOGY
  • E. UNIVERSAL TRANSVERSE MERCATOR (UTM)
  • F. STATE PLANE COORDINATES (SPC)
  • REFERENCES
  • DISCUSSION AND EXAM QUESTIONS
  • NOTES

    This unit needs many overhead illustrations. Of course, the best figures are in commercially published books. To avoid copyright infringements, we have not included the masters for overheads needed here. Instead, you are directed to the References which lists several basic texts with good illustrations. We have included suggested overheads giving references and specific page numbers to help you locate suitable figures.

    UNIT 27 - MAP PROJECTIONS

    Compiled with assistance from Vicki Chmill, University of California, Santa Barbara

    A. INTRODUCTION

    Relevance to GIS

    B. DISTORTION PROPERTIES

    Tissot's Indicatrix

    Conformal (Orthomorphic)

    Equal area (Equivalent)

    Equidistant

    C. FIGURE OF THE EARTH

    1. Plane

    2. Sphere

    3. Spheroid or ellipsoid of rotation

    Accuracy of figures used

    D. GEOMETRIC ANALOGY

    Developable surfaces

    1. Planar or azimuthal

    2. Conic

    3. Cylindrical

    4. Non-Geometric (Mathematical) projections

    E. UNIVERSAL TRANSVERSE MERCATOR (UTM)

    Transverse Mercator Projection

    Zone System

    Distortion

    Coordinates

    Advantages

    Disadvantages

    F. STATE PLANE COORDINATES (SPC)

    Advantages

    Disadvantages

    Use in GIS

    REFERENCES

    Maling, D.H., 1973. Coordinate Systems and Map Projections, George Phillip and Son Limited, London.

    Robinson, A.H., R.D. Sale, J.L. Morrison and P.C. Muehrcke, 1984, Elements of Cartography, 5th edition, John Wiley and Sons, New York. See pages 56-105.

    Snyder, J.P., 1987. Map Projections - A Working Manual, US Geological Survey Professional Paper 1395, US Government Printing Office, Washington.

    Strahler, A.N. and A.H. Strahler, 1987. Modern Physical Geography, 3rd edition, Wiley, New York. See pages 3-8 for a description of latitude and longitude and various appendices for information on coordinate systems.

    DISCUSSION AND EXAM QUESTIONS

    1. Define the three standard properties of map projections: equal-area, equidistant and conformal. Discuss the relative importance of each for different applications. What types of applications require which properties?

    2. What type of projection would you expect to be used in the following circumstances, and why?

    a. an airline pilot flying the North Atlantic between New York and London.

    b. a submarine navigating under the ice of the North Pole.

    c. an agricultural scientist assembling crop yield data for Africa.

    d. an engineer planning the locations of radio transmitters across the continental US.

    3. What map projections would you choose in designing a workstation to be used by scientists studying various aspects of global environmental change?

    4. By examining the list of SPC systems adopted by the states, what can you deduce about the criteria used to determine the projection adopted and the number of zones used? You will need a map of the US showing the boundaries of states. Are there any surprising choices?


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