UNIT 30 - STORAGE OF COMPLEX OBJECTS

UNIT 30 - STORAGE OF COMPLEX OBJECTS

Compiled with assistance from David H. Douglas, University of Ottawa

  • A. INTRODUCTION
  • B. REPRESENTATION OF SIMPLE SPATIAL OBJECTS
  • C. STORAGE OF OBJECT ATTRIBUTES
  • D. REPRESENTATION OF TOPOLOGY
  • E. DISADVANTAGES OF ARC-BASED REPRESENTATIONS
  • F. OTHER ISSUES ABOUT DATA STRUCTURES
  • REFERENCES
  • DISCUSSION AND EXAM QUESTIONS
  • NOTES

    UNIT 30 - STORAGE OF COMPLEX OBJECTS

    Compiled with assistance from David H. Douglas, University of Ottawa

    A. INTRODUCTION

    B. REPRESENTATION OF SIMPLE SPATIAL OBJECTS

    C. STORAGE OF OBJECT ATTRIBUTES

    D. REPRESENTATION OF TOPOLOGY

    Relationships in networks

    Relationships between areas

    The CanSIS data structure

    E. DISADVANTAGES OF ARC-BASED REPRESENTATIONS

    F. OTHER ISSUES ABOUT DATA STRUCTURES

    REFERENCES

    Burrough, P.A., 1986. Principles of Geographical Information Systems for Land Resources Assessment, Clarendon Press, Oxford. See Chapter 2.

    Haralick, R.M., 1980. "A Spatial Data Structure for Geographic Information Systems," in H. Freeman and G.G. Pieroni, eds., Map Data Processing, Academic Press, New York.

    Peuker, T.K., and N. Chrisman, 1975. "Geographic Data Structures," American Cartographer 2(1):55-69.

    van Roessel, J.W., and E.A. Fosnight, 1984. "A relational approach to vector data structure conversion," Proceedings, International Symposium on Spatial Data Handling, Zurich, pp. 78-95.

    DISCUSSION AND EXAM QUESTIONS

    1. Make a list of the kinds of relationships which can exist between pairs of spatial objects, for each pair of points, lines and areas, e.g. point to point, point to line, area to point etc. Are there any examples of relationships between triples of objects, e.g. point-point-point?

    2. Write out the CanSIS data structure for a simple map of three or four polygons, forming an equal or smaller number of objects (include the x,y coordinate pairs) (need to include a drawn example).

    3. The GIS industry has traditionally provided data models which assume that within any one layer of the database, polygon objects do not overlap, and exhaust the space available. Comment on the degree to which this assumption has limited the application of GIS databases in specific areas. Are these sufficiently significant to warrant a change of data models in the future?

    4. Discuss areas of application in which the concept of a complex feature type would be useful. What operations would you want to perform on complex and simple features respectively?


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