u12-RELATIONSHIPS AMONG SPATIAL OBJECTS

u12-RELATIONSHIPS AMONG SPATIAL OBJECTS - UNIT 12 -...

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Sheet1 Page 1 UNIT 12 - RELATIONSHIPS AMONG SPATIAL OBJECTS <toc.html#UNIT12> UNIT 12 - RELATIONSHIPS AMONG SPATIAL OBJECTS Compiled with assistance from Gerald White, California State University, Sacramento # A. INTRODUCTION <#SEC12.1> * Three types of relationship <#SEC12.1.1> # B. EXAMPLES OF SPATIAL RELATIONSHIPS <#SEC12.2> * Point-point <#SEC12.2.1> * Point-line <#SEC12.2.2> * Point-area <#SEC12.2.3> * Line-line <#SEC12.2.4> * Line-area <#SEC12.2.5> * Area-area <#SEC12.2.6> # C. CODING RELATIONSHIPS AS ATTRIBUTES <#SEC12.3> * Example - "flows into" relationship <#SEC12.3.1> * Example - "is contained in" relationship <#SEC12.3.2> # D. OBJECT PAIRS <#SEC12.4> # E. CARTOGRAPHIC AND TOPOLOGICAL DATABASES <#SEC12.5> * Strict definition of "topological" <#SEC12.5.1> * Usage of "topological" in GIS <#SEC12.5.2> # F. PLANAR ENFORCEMENT <#SEC12.6> * Process <#SEC12.6.1> * Objective <#SEC12.6.2> # G. RELATIONSHIPS IN RASTER SYSTEMS <#SEC12.7> # REFERENCES <#SEC12.8> # EXAM AND DISCUSSION QUESTIONS <#SEC12.9> # NOTES <#SEC12.10> 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
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Sheet1 Page 2 Compiled with assistance from Gerald White, California State University, Sacramento A. INTRODUCTION <#OUT12.1> * there are a vast number of possible relationships in spatial data * many are important in analysis o e.g. "is contained in" relationship between a point and an area is important in relating objects to their surrounding environment o e.g. "intersects" between two lines is important in analyzing routes through networks * relationships can exist between entities of the same type or of different types o e.g. for each shopping center, can find the nearest shopping center (same type) o e.g. for each customer, can find the nearest shopping center (different types) Three types of relationship <#OUT12.1.1> 1. relationships which are used to construct complex objects from simple primitives o e.g. relationship between a line (chain) and the ordered set of points which defines it o e.g. relationship between an area (polygon) and the ordered set of lines which defines it 2. relationships which can be computed from the coordinates of the objects o e.g. two lines can be examined to see if they cross - the "crosses" relationship can be computed o e.g. areas can be examined to see which one encloses a given point - the "is contained in" relationship can be computed o e.g. areas can be examined to see if they overlap - the "overlaps" relationship 3. relationships which cannot be computed from coordinates - these must be coded in the database during input o e.g. we can compute if two lines cross, but not if the highways they represent intersect (may be an overpass) o some databases allow an entity called a "complex object", composed of "simple objects", e.g. objects representing
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This note was uploaded on 10/05/2010 for the course GEO 591 taught by Professor Davidm.mark during the Fall '10 term at SUNY Buffalo.

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u12-RELATIONSHIPS AMONG SPATIAL OBJECTS - UNIT 12 -...

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