Conceptual models of real world
      geographical phenomena


    From real world to abstraction
●


    Conceptual model...
Is the geographic world a
jig-saw puzzle of polygons,
 or a club-sandwich of data
   layers? (Couclelis, 1992)
Maps and GIS are models of reality
  They emphasize some aspects of reality in a
  cartographic (and database) representat...
Entities or Fields
    Entities
●


        space is peopled with 'objects'
    –

        discontinuous objects, that are...
Entities or Fields
    Fields
●


        space in terms of continuous Cartesian coordinates
    –
        in two or three...
Layers
        a logical separation of
    ●

        mapped information
        according to theme
        each layer is ...
Data Models & Representation
    Spatial/Geometric
●


        location or spatial disribution of a phenomenon
    –

    ...
Basic Data Models
   Vector Data
   Model (entities)

   Raster Data
   Model (fields)
Vector Data Model
   The directional linear connection between two
   points
   The root of vector data model lies in
   c...
Vector Data Model
   A series of points that are connected or joined form a
   line. A type of line feature that does not ...
Object representation
               Point (oil wells, fire hydrant)



               Lines (railway, roads, rivers)




...
Topology
  Connections & relationships between geographic
  features based on location.
  Spatial relationships are implic...
Raster Data Models
   Establishes a pattern of similar grids or cells over a
   geographic area
   The location of each ce...
Raster Data Model
3


     5
10
                +                 2


                           4
                                         ...
Raster or Vector?
Comparison between raster and vector
                         Raster    Vector
  Data collection         Rapid     Slow
  ...
Attribute Data
Is the geographic world a
jig-saw puzzle of polygons,
 or a club-sandwich of data
   layers? (Couclelis, 1992)
References
Burrough, P. A. & McDonnel R.A. 1998. Principles of
 Geographical Information System. New York, USA:
 Oxford Un...
License of this Document
This work is licensed under a Creative Commons License.
 http://creativecommons.org/licenses/by-s...
Conceptual models of real world geographical phenomena (epm107_2007)
Conceptual models of real world geographical phenomena (epm107_2007)
Conceptual models of real world geographical phenomena (epm107_2007)
Conceptual models of real world geographical phenomena (epm107_2007)
Conceptual models of real world geographical phenomena (epm107_2007)
Conceptual models of real world geographical phenomena (epm107_2007)
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Conceptual models of real world geographical phenomena (epm107_2007)

  1. 1. Conceptual models of real world geographical phenomena From real world to abstraction ● Conceptual models ● Data models and representation ●
  2. 2. Is the geographic world a jig-saw puzzle of polygons, or a club-sandwich of data layers? (Couclelis, 1992)
  3. 3. Maps and GIS are models of reality They emphasize some aspects of reality in a cartographic (and database) representation while ignoring or greatly simplifying other aspects of reality. Abstraction the process of interpreting what can be sensed from the real world into symbols Data Modeling the process of abstraction from the real world for the purpose of representation in a GIS (or other information system)
  4. 4. Entities or Fields Entities ● space is peopled with 'objects' – discontinuous objects, that are spatially delimited by – precise edges and, in case, characterized by specific attributes recognize the entity then define boundaries and – location “discrete data” – administrative boundaries, phonelines, – transportation networks
  5. 5. Entities or Fields Fields ● space in terms of continuous Cartesian coordinates – in two or three dimensions phenomena that are continuous almost everywhere – in their definition domain attribute vary smoothly and continuously over space – understand spatial variation then recognize 'thingsquot; – “continuous data” – elevation, temperature, satellite data –
  6. 6. Layers a logical separation of ● mapped information according to theme each layer is thematic ● and reflects either a particular use or a characteristics series of overlays ●
  7. 7. Data Models & Representation Spatial/Geometric ● location or spatial disribution of a phenomenon – Attributes ● descriptive information associated with geometry –
  8. 8. Basic Data Models Vector Data Model (entities) Raster Data Model (fields)
  9. 9. Vector Data Model The directional linear connection between two points The root of vector data model lies in cartography Basic elements are points with an x,y coordinates Series of points that when joined with straight lines, form the graphic representation of that feature unlimited precision
  10. 10. Vector Data Model A series of points that are connected or joined form a line. A type of line feature that does not intersect with any other line is referred to as arcs. A series of arcs defined a polygon. A series of polygon is a surface within the vector system.
  11. 11. Object representation Point (oil wells, fire hydrant) Lines (railway, roads, rivers) Area/Polygon (land parcel, forest stand, lakes)
  12. 12. Topology Connections & relationships between geographic features based on location. Spatial relationships are implicit on map sheets. Standing on a street corner looking at a map is a pretty easy way to identify intersecting streets and properties that are adjacent. The computer ‘sees’ these relationships by means of explicitly encoded topology.
  13. 13. Raster Data Models Establishes a pattern of similar grids or cells over a geographic area The location of each cell is defined by its row and column indices The value assigned to a cell either reflects the dominant feature (attribute) at that grid space or indicates the presence of a preferred feature in case where two or more features are present within a single grid space Basic unit in a raster is a cell (or grid or pixel) Analytically more powerful than the vector based GIS
  14. 14. Raster Data Model
  15. 15. 3 5 10 + 2 4 5 = 10 9 20 Direct calculations using raster layers
  16. 16. Raster or Vector?
  17. 17. Comparison between raster and vector Raster Vector Data collection Rapid Slow Data volume Large Small Graphic treatment Average Good Data structure Simple Complex Geometrical accuracy Low High Analysis in network Poor Good Area analysis Good Average Generalization Simple Complex
  18. 18. Attribute Data
  19. 19. Is the geographic world a jig-saw puzzle of polygons, or a club-sandwich of data layers? (Couclelis, 1992)
  20. 20. References Burrough, P. A. & McDonnel R.A. 1998. Principles of Geographical Information System. New York, USA: Oxford University Press Neteler, M. & Mitasova, H. 2004. Open source GIS: a GRASS GIS approach, 2nd edition. The Netherlands: Kluwer Academic Publishers Heywood, I. et. al. 1998. An Introduction to Geographical Information System. New York, USA: Addison Wesley Longman
  21. 21. License of this Document This work is licensed under a Creative Commons License. http://creativecommons.org/licenses/by-sa/2.5/deed.en License details: Attribution-ShareAlike 2.5 You are free: - to copy, distribute, display, and perform the work, - to make derivative works, - to make commercial use of the work, under the following conditions: Attribution. You must give the original author credit. Share Alike. If you alter, transform, or build upon this work, you may distribute the resulting work only under a license identical to this one. For any reuse or distribution, you must make clear to others the license terms of this work. Any of these conditions can be waived if you get permission from the copyright holder. Your fair use and other rights are in no way affected by the above. Emmanuel P. Sambale. November, 2006 http://esambale.wikispaces.com

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