UNIT 12 - RELATIONSHIPS AMONG SPATIAL OBJECTS

UNIT 12 - RELATIONSHIPS AMONG SPATIAL OBJECTS

Compiled with assistance from Gerald White, California State University, Sacramento

  • A. INTRODUCTION
  • B. EXAMPLES OF SPATIAL RELATIONSHIPS
  • C. CODING RELATIONSHIPS AS ATTRIBUTES
  • D. OBJECT PAIRS
  • E. CARTOGRAPHIC AND TOPOLOGICAL DATABASES
  • F. PLANAR ENFORCEMENT
  • G. RELATIONSHIPS IN RASTER SYSTEMS
  • REFERENCES
  • EXAM AND DISCUSSION QUESTIONS
  • NOTES

    This final unit in the spatial databases module looks at the complex issue of relationships and how they can be coded. The important concept of planar enforcement, introduced here, is referred to several times in later units.

    UNIT 12 - RELATIONSHIPS AMONG SPATIAL OBJECTS

    Compiled with assistance from Gerald White, California State University, Sacramento

    A. INTRODUCTION

    Three types of relationship

    B. EXAMPLES OF SPATIAL RELATIONSHIPS

    Point-point

    Point-line

    Point-area

    Line-line

    Line-area

    Area-area

    C. CODING RELATIONSHIPS AS ATTRIBUTES

    Example - "flows into" relationship

    Example - "is contained in" relationship

    D. OBJECT PAIRS

    E. CARTOGRAPHIC AND TOPOLOGICAL DATABASES

    Strict definition of "topological"

    Usage of "topological" in GIS

    F. PLANAR ENFORCEMENT

    Process

    Objective

    G. RELATIONSHIPS IN RASTER SYSTEMS

    REFERENCES

    Burrough, P.A., 1986. Principles of Geographical Information Systems for Land Resources Assessment. Clarendon, Oxford. Chapter 2 describes objects, attribute tables and relationships.

    Goodchild, M.F., 1988. "Towards an enumeration and classification of GIS functions," Proceedings, IGIS '87. NASA, Washington DC 2:67-77. Defines and discusses object pairs.

    Keating, T., W. Phillips and K. Ingram, 1987. "An integrated topologic database design for geographic information systems," Photogrammetric Engineering and Remote Sensing Vol. 53. Good discussion of topological and cartographic database models.

    EXAM AND DISCUSSION QUESTIONS

    1. Discuss the use of planar enforcement for street networks, and the problems presented by overpasses and underpasses. Can you modify the basic rules to maintain consistency but allow for such instances?

    2. What additional examples of relationships can you devise in each of the six categories used in section B?

    3. Why have designers of raster GIS not commonly devised ways of coding spatial relationships between objects in their systems? Is this likely to change in the future, and if so, why?

    4. "Topology is what distinguishes GIS from automated cartography". Discuss.


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