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Spatial Databases - Representation Spring, 2015 Ki-Joune Li.
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Transcript of Spatial Databases - Representation Spring, 2015 Ki-Joune Li.
Spatial Databases- Representation
Spring, 2015
Ki-Joune Li
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Spatial Databases
Entity-Based Databases vs. Field-Based Databases Entity-Based Databases
Set of Spatial Objects Non-Spatial Attributes for each object
Field-Based Databases No clear boundary of an object No non-spatial attributes
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Entity-Based Spatial Databases
Feature: Meaningful Spatial Entity Example
Building: a meaningful entity Edge: a spatial piece
Each feature has Geometry OID Non-spatial Attributes
Spatial Database Set of Features Set of Relationships between Features
Representation of Geometry Raster Model Vector Model Constrained Representation
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Representation of Geometry: Raster Model
Raster Model A geometric object: set of pixels or tessels (mosaics) A value is assigned to each pixel
Example
Pros and Cons
Pollution Area
Non-Pollution Area
Pros Cons
1. Simple
2. Easy to Collect
Example: Satellite Image
1. Huge
2. Difficult to manipulate Example: Rotation, Zooming
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Irregular Tessellation
Regular Raster Model Huge Size of Data To reduce the size, Irregular Tessellation
Irregular Tessellation Irregular Size Irregular Shape
Irregular Size K-D tree Quadtree
Region Quadtree Point Quadtree
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K-D tree
Partitioning of a space bipartition X-axis and Y-axis alternatively x1
y1
x11 x12
x1
y1
x11
x12
y12
y12
< >
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Quadtree
Extension of KD-tree: KD-tree: binary split Quadtree 4-way equi-split instead Quadrant
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Point Quadtree
A variation of quadtree Center of division is given by (x,y) More flexible than region quadtree
Analysis by quadtree Area computation Difference
p1
p2 p3
p1p2
p3
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Linear Quadtree
Linearization of Quadtree Transformation of 2-D space to 1-D space By Space Filling Curve
Peano key is assigned to each quadrant
N-order Hilbert Column-wise
6
13
11
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Linear Quadtree
N-order Peano Key Bit Interleaving Method
1. Binary representation of coordinates (10,01)
2. Bit-Interleaving x = 1 0 y = 0 1
Peano key = 1 0 0 1 = 9
00 01 10 11
00
01
10
11
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Linear Quadtree
Each Quadrant Represented by (kpeano, size)
Size:
Object is represented by a set of pairs (k,s)
2n split
Size 2
Size 0
Size 1
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Vector Model
Geometric object is represented by its Coordinates (x,y), or (x,y,z)
Geometric type Point (x,y) Line (x1,y1,x2,y2) or (p1, p2) Polyline (x,y)* or p* Polygon: Closed polyline
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Example: OGC Simple Feature Geometry
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Database Schema for Vector Model
By Relational Data Model Point and Line: No problem Polyline, Polygon
1st Normal Form of relational model Atomic type only Set type is not allowed Polyline: ordered set of points
Geo-relational model: Based on Winged-Edge Topology
By Object-Oriented Data Model or OR Model Provide Set type Provide Polygon, Polyline Type
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Winged Edge Representation
Example
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Winged Edge Representation: Topology
Point Topology Face Topology
Line Topology
Point # Start Line # Start Line #Face #
Line # Starting Point #
Ending Point #
LeftLine #
RightLine #
LeftFace #
RightFace #
Left Line
Right LineStart Point
End Point
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Winged Edge Representation: Geometry
Line Geometry Table
Line # Starting Point Intermediate Points Ending Point
Why Line-Oriented Representation ?