The Nature of Geographic Information

1. Overview


Chapters 6 and 7 consider the origins and characteristics of the framework data themes that make up the United States' proposed National Spatial Data Infrastructure (NSDI). Chapter 6 discussed the geodetic control and orthoimagery themes. This chapter describes the origins, characteristics, and current status of the elevation, transportation, hydrography, governmental units, and cadastral themes.


Students who successfully complete Chapter 7 should be able to:

  1. given a regular or irregular array of spot elevations, construct a triangulated irregular network, interpolate contour intervals and draw contour lines;
  2. compare vector and raster representations of terrain elevation;
  3. acquire and view digital elevation data from the National Elevation Dataset;
  4. calculate an interpolated spot elevation based on neighboring elevations;
  5. contrast the characteristics of three global elevation data products;
  6. describe the characteristics and current status of the NSDI hydrography, transportation, and governmental units themes as implemented in USGS' National Map; and
  7. interpret the size and relative location of a land parcel designated in terms of the U.S. Public Land Survey System.

"Try This!" Activities

Take a minute to complete any of the Try This activities that you encounter throughout the chapter. These are fun, thought provoking exercises to help you better understand the ideas presented in the chapter.

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