GIS 201 Chapter 11

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GIS 201 Chapter 11
2011-09-14 19:12:48
Coordinate systems

Terms and concepts from chapter 11 of the Price text.
Show Answers:

  1. How many degrees are there around the equator?
  2. In a geographic coordinate system, longitudes fall in the range from _____________.
    -180 to 180 degrees
  3. Latitudes fall in the range from __________________.
    -90 at the south pole to 90 at the north pole.
  4. What is a spheroid?
    An oblong sphere with a major and minor axis; AKA ellipsoid.
  5. What is the geoid?
    The measurement of the earth's radius with respect to a datum.
  6. On what spheroid is the North American Datum of 1983 based?
  7. What do cylindrical projections preserve?
    Shape or direction at the expense of area and distance.
  8. What do conic projections preserve?
    Area or distance at the expense of direction and shape.
  9. How are azimuthal projections produced?
    By placing a plane tangent or secant to the sphere.
  10. What do azimuthal projections preserve?
    Area or distance at the expense of direction or shape.
  11. What is the latitude of origin?
    The y=0 line.
  12. What is a world file?
    A 6-line text file holding the parameters needed to georeference the raster.
  13. What is RMSE?
    Root Mean Square Error; after rectification of a raster, there may still be offsets between the two sets of ground control points, and this RMSE serves as a measure of the accuracy of the transformation.
  14. How should rasters be resampled?
    Rasters containing categorical data should be resampled w/the nearest neighbor method; continuous rasters should be resampled with the bilinear method.
  15. How many zones are there in the UTM system?
  16. What projections does the State Plane Coordinate System use?
    • Lambert Conformal Conic (for east-west zones)
    • Transverse Mercator (for north-south zones)
    • Oblique Mercator
  17. What is the X/Y domain?
    The range of allowable x-y values that can be stored in a feature class.
  18. What is the extent of a data layer?
    The range of the x-y coordinates of the features actually in the feature class.
  19. What does the Project tool do?
    Acts on the x-y coordinates of a layer and converts them to a different coordinate system, producing a new feature class and leaving the original feature class unchanged. Should be used only on layers with correct coordinate system definitions.
  20. What does the Define Projection tool do?
    Changes only the coordinate system label of the feature class, without affecting the coordinates inside. Should only be used on on a data set that has an unknown coordinate system or on a data set that was previously mislabeled and needs to be fixed.