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Vector & Raster Data Models

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Vector & Raster Data Models Powered By Docstoc
					Data Models
   Vector Data




   Raster Data
Data Models
   Simple: How the world is modeled
       In simple terms: Raster or Vector data
   Expanded version:
    A conceptual representation scheme…
    … using an Object Framework (or frameworks)
     Topology, Linear Referencing, Network
             PolylineM
             Connected
 Topology
   A branch of geometry that deals with the
    properties of a figure that remain unchanged
    even when the figure is bent, stretched, or
    otherwise distorted
   Spatial relationships (inside/outside, beside)

Topology   -- knowledge about relative spatial positioning
           -- managing data cognizant of shared geometry
Topography -- the form of the land surface,
                   in particular, its elevation
    Topology and Coverages (ArcInfo)

   Multiple files stored in multiple file folders…




                             ArcCatalog
    Coverages (ArcInfo workstation)
   Topology is explicitly represented & stored
   “Point in polygon”
       Points used to make
        lines (can be reused)
       Lines used to make
        polygons (can be
        reused)
   No overlaps / slivers
       Also no islands or
        donuts…
                                                                              Points File
       “Point in polygons”…                                                   1    3,4
                                                                                          Polygons File
                                                                              2    4,4
                                                                              3    4,2    A 1, 2, 3, 4, 1
      5
                      11                                          12          4    3,2    B 2, 5, 6, 3, 2
      4                                                                       5    5,4    C 4, 3, 8, 9, 4
                                            1
                                                       2          5           6    5,2    D 3, 6, 7, 8, 3
      3                            13                 14          15          7    5,0    E 11, 12, 5, 1, 9,
                               E                      A           B           8    4,0       10, 11
      2
                                            4                      6          9    3,0
                                                       3
                                                      16          17          10   1,0
      1
                                                      C                       11   1,5
                                                                                          Label Points
                      10                    9
                                                                  D                         A 13
                                                          8           7       12    5,5
      0
                                                                                            B 14
                                                                              13 2,3        C 15
                     1             2            3             4           5
                                                                              14 3.5,3      D 16
                                                                              15 4.5,3      E 17
                                                                              16 3.5,1
http://www.utdallas.edu/~briggs/poec5319/struct.ppt                           17 4.5,1
      Geodatabases (ArcGIS)
      Feature Classes
      Feature Datasets
      Relationships…
      Domains…




http://www.geog.ucsb.edu/~ta176/g176b/lab3/lab3_graphics/gdb_newobjects_9_ed.gif
    Geodatabases (ArcGIS)
   Topological rules are stored outside of the data
    layer itself
       Spatial relationships (coincident/adjacent geometry)
            Lines can/cannot cross or must be coincident
            Points must be within polygons
            Polygons must be adjacent
            Etc.
       Can exist between different layers
   Coverages are a topological data structure.
    Geodatabases can make use of topological
    relationships and rules…
      Geodatabases Topology Rules




http://webhelp.esri.com/arcgisdesktop/9.2/index.cfm?TopicName=Topology_rules
      Geodatabases Topology Rules (examples)
                                                                  No overlaps or
                                                                 gaps for polygons



                     Lines must                                                  Points must be
                    be coincident                                                 w/in a polygon



  Lines must connect
     (no dangles)
                                                                               Points must be on a line




http://webhelp.esri.com/arcgisdesktop/9.2/index.cfm?TopicName=Topology_rules
Vector Data Models and Topology
   Network of linear features (connected so that
    flows can be modeled)
       Roads, streams
   Complete coverage of areas
       Watershed sub-basins
       Land cover
       Census tracts
      Network Topology
         Utility networks (water, electric, gas)
               Locations and connections of features is important
               Pipes, valves, pipe size/capacity, flow direction…




http://www.bigskywatersewer.com/projects-sb/Silverbow%20DEQ%20progress.jpg
    Network Data Model: Object Framework
   Vector
       PolylineM (vertex topology)
   Connected objects
       Networks (line topology)
Network Data Model: Connected Objects
   Road network
   Connected Coverage
    Frameworks (Network)
   The meaning of each
    object is dependent on
    connection to other
    elements in the network
   Used when topological
    relationships are
    important

				
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posted:6/9/2012
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Lingjuan Ma Lingjuan Ma
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