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

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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 ?