1. Lecture 3 spatial data modeling and management

2. Spatial data structure Comparison of vector and raster
spatial data modeling and management
Spatial data structure
Comparison of vector and raster
Introduction to spatial database
Data models in traditional database
Data base for GIS
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3. What is a data model ？ The heart of any GIS is data model
A data model is a set of constructions for describing and representing selected aspects of the real world in a computer
There is no single type of GIS data model that is best for all circumstances
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4. The role of a data model in GIS
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5. GIS data models CAD 、geographical and image GIS data model
Raster Data Model
Vector Data Model
Object Data Model
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6. 2017年4月24日

7. The CAD data model
A CAD model focuses on feature drawing only ,so that it does not represent any kind of relationships between objects
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8. Image data model
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9. Difference between image data model and raster data model
Image data do not have attribute table attached,so that they have only one attribute field.
Raster data have attribute table that can be joint to other tables ,so that they can have multiple attribute field.
application：
image data---image processing
raster data---spatial analysis and modeling
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10. Vector data model
Vector data model uses a set of coordinate and relationship to represent real world objects。
Geometry objects:
Point:single point
Line：string
Area：closed loop
other vector model:
Triangulated Irregular Network:surface
Region
Dynamic segmentation:network
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11. Vector data model：acquisition
Surveying instruments(total station、GPS、level,etc.)
Digitize map
Indirect methods:
Rater to vector
Data from spatial analysis
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12. Vector data model：how to describe
Storage and management of vector data
Associate geometry data and attribute data
Relationship of spatial objects
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13. Vector data model（cont.）
Vector data model—the spaghetti structure
Only to record position and attribute information of the spatial object,but not topological relationship
Storage：
Independence ：spatial objects with its geometry information
Point dictionary：coordinate storage is separated from its spatial objects
Characters:
no topological relationship ,so that only can be used to presentation and simple query of spatial object
Exists data redundancy
Can not keep consistency of the data,for the common part repeats storage
Spatial analysis is more complicated
Can not deal with the operation of polygon
Appropriate applications：
For the disadvantages that stated above,this data structure can be used to map and general query,but not for spatial analysis
Vector data model（cont.）
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14. Vector data model（cont.）
point: ( x ,y )
line: ( x1 , y1 ) , (x2 , y2 ) , … , ( xn , yn )
area: ( x1 , y1 ) , (x2 , y2 ) , … , ( x1 , y1 )
Encoding
database ID
Attribute
Geometry No X Y 1 11 22 2 33 44 … n 55 66
point
Point
dictionary
line
area
Encoding of spatial objects
Sole
Associate the attribute and position
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15. Vector data model:example of spaghetti structure
polygon
code
coordinate A
t123
1，2
3，4 … B
t124
5 , 6
No. of point
coordinate 1 2 3 4 5
1，2
3，4
5，6
7，8 … 1 2 3 4 5 6 7 A B
polygon
code
No. of point A B
T123
t124
1,2,3,4,7,6,1
1,6,7,4,5,1
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16. Vector data model（cont.）
Vector data model:the topological structure
Not only expressed the position and attribute of objects,but also relationship between objects
Generally the topological relationship is conjunction
The conjunction can be expressed in full expression and part expression
Storage
Directly storage
Serial pointer
Topological relationship and data share
Conditions of using topological relationship
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17. Vector data model（cont.）
Vector data model : full expression A8 B1 B2 B3 B4 A1 A2 A3 A4 A5 A6 A7 N1 N2 N3 N4 N5 M
Area
Arc
Node N1 B2 N2 N4 N3 B3 B4 B1 A1 A2 A6 A5 A4 A3 A7 A8 N5
Polygon-arc
Polygon
Arc
Arc-node
from
Arc-polygon
Left
Node-arc
Nod e to
Right
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18. Vector data model（cont.）
Vector data model:part expression
Using part table to describe topological relation
System9：polygon-arc 、arc-node
DIME：arc-node、arc-polygon
The topological relationship is all in the above
states in current GIS
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19. Topological structure：how to describe in computer
Vector data model（cont.）
pointer
polygon-arc、node-arc：it is not convenient directly storage for unequal length of record
Example:POLYVRT
TIGER
Directly storage
Arc/Info、GeoStar
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20. Vector data model£¨cont.£©
Topological structure:topological relationship and data share To keep data consistent
Move node with topological relation
Move node with no topological relation
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21. Topological relations：when to use topological structure
Vector data model（cont.）
Application
Map and general query can not use topological structure
Topological relation can be used to spatial analysis
Objects can be described with topological relation
Polygon object：polygon-arc、arc-polygon
Network object：node-arc、arc-node
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22. Vector data model：attribute
Type
type ：what is the object?
explanation information：different attribute with the same object
description
Encode
Attribute table
The item of attribute table depends on users
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23. Map graphic data to attribute data linkage
Spatial objects
point ID
Encoding
Coordinate
related line
Precision
Control-point
grade
Geodesic
organization
years ……
line ID
Encoding
Coordinate
from、to、left、right
Material
Grade
Build
time
Breadth
Management
organization ……
area ID
Encoding
No. of
boundary
Build
time
owner
Building
organization
structure ……
Type of object and attribute
Encoding
Name of
object
Map color
Type of
geometry
Map sign
encoding
Attribute
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24. Triangulated irregular network1 2 3 6 5 8 7 9 11 10 4 A B C D E F G H I J K L M N
EDGES
adjacent A B C D E F G H I J K L M N
B, K
A, C, L
B, D
C, E, L
D, F
E, G
F, H, M
G, I
H, J, N
I, K
A, J, N
B, D, M
G, L, N
I, K, M
NODES
node# A B C D E F G H I J K L M N
1, 6, 7
1, 7, 8
1, 2, 8
2, 8, 9
2, 3, 9
3, 4, 9
4, 9, 10
4, 5, 10
5, 10, 11
5, 6, 11
6, 7, 11
7, 8, 9
7, 9, 10
7, 10, 11
X-Y Coordinates
node#
coordinates 1 2 3 11
. . .
x1, y1
x2, y2
x3, y3
x11, y11
Z Coordinates
node#
z_value 1 2 3 11
. . . z1 z2 z3
z11
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25. Triangulated irregular network (cont.)
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26. Dynamic segmentation
Dynamic segmentation associates multiple sets of attributes to any portion of a linear feature
Elements of dynamic segmentation :
Route--- A route is a linear feature on which attributes are defined
Measure---Each route is associated with a measurement system
Events---Attributes associated with a route
Advantage of dynamic segmentation
Define linear feature within a line coverage
Work with data in route-measure format
Apply attributes in route-measure to any part of a route without modifying underlying coordinate data
Used to network analysis
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27. Vector data structure：advantages and disadvantages
Distinct location and implicit attribute
Represent spatial relation with topological relationships
Object-based operation with high accuracy and less data redundancy
Difficult to combine with RS data
High quality graphics
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28. Raster data structure:contents
Definition
Divides the entire study area into a regular grid of cells,each cell contains a single value
In rater data structure
Point：pixel or cell
Line：represented in cluster of adjacent pixel。
Area：pixel with same attribute that are congregated
Data sources：
Remote sense image
Scanner
Vector to raster
Manual
Raster coordinates
Compress raster data
Raster layers
Rater data file structures
Advantage and disadvantage of raster data structure
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29. Area
Line
Point
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30. Raster data structure：coordinate system and parameters
Grid direction
Resolution
X：Row
North-west coordinate
（XWS，YWS）
Y：Col
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31. Raster data structure：assign value to cellB
Midpoint
Percentage
importance
Area A C A AB
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32. Raster data structure:compression1 2 3 4 5 6 7 A R G 1 4 3 2 5 8 7 6
Chain codes
Number of start row and
column,unit vector
R: (1,5),3,2,2,3,3,2,3
Run-length codes
Recording on row or column
No. of row ,attribute, number of repeats
1, A, 4, R, 1, A, 4
Block codes
Rectangle
Initial position, radius, value
(1,1,3,A),(1,5,1,R),(1,6,2,A),¡­
Quarter-tree
codes SE SW NW NE G G A G A G A
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33. Hierarchy of the raster data structureZ
Building
Forest
Soil
relief Y X
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34. File structure of the raster data structure
Each cell is referenced
directly , Map file
Each overlay is referenced
directly, Map file
Each mapping unit is referenced
directly
Point
X coordinate
Overly
Point
(X,Y) coordinate
Overlay
tile
Y coordinate
Z value
Scale
Overlay values
Next
point …
Mapping
unit 1
Lable
Next overlay
values … …
Display
symbol …
Attribute
Next
overlay
Next point
X,Y
Coordinates
pairs … …
Next mapping
unit …
Next
overlay
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35. Raster data structure:advantages and disadvantages
Spatial object represented in discrete cell value
Location is implicit and attribute is distinct
Simple data structure and easy to combine with RS data
Existing errors in geometry and attribute
Difficult to build the relationship between spatial objects
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36. Geometry bias Attribute bias a b c 3 4 5 Ac distance: 7/4 (5)
area: (6)
Geometry bias
Attribute bias
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37. Comparison of vector and raster data model
Vector model
advantages：
It provides a more compact data structure than the raster model
It provides efficient encoding of topology ,and as a result ,more efficient;implementation of operations that require topological information ,such as network analysis
The vector model is better studies to supporting graphics that closely approximate hand-drawn maps
disadvantages：
It is a more complex data structure than a simple raster
Overlay operations are more difficult to implement
The representation of high spatial variability is inefficient
Manipulation and enhancement of digital images can not be efficiently done in the vector domain
Raster model
Comparison of vector and raster data model
advantages：
It is a simple data structure
Overlay operation are easily and efficiently implemented
High spatial variability is efficiently represented in a rater format
The raster format is more or less required for efficient manipulation and enhancement of digital images
disadvantages：
The raster data structure is less compact
Topological relationships are more difficult to represent
The output of graphic is less aesthetically pleasing because boundaries tend to have a blocky appearance rather than the smooth lines of hard-drawn maps.this can be overcome by using a very large numbers of cells ,but may result in unacceptable large files
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38. Principles of selecting data models
Object or fields
Acceptable data
Necessary accuracy of spatial objects location
Topological relationships
Type of spatial analysis
Type of map
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39. Spatial data management：spatial database
A data base is defined as structured collection of information on a defined subject
characters：
Data is independent on application programs
Relationship of data represent the connection of information in the real world
Conventional data base management structures
Hierarchy database structure
Network database structure
Relational database structure
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40. Spatial data management：spatial database（cont.）
A spatial data base is a collection of geographical data and information on a defined area
characters：
Huge data quantity
Location and attribute data combined
Broad application areas
Features of spatial data base
spatiality
Non-structured
Spatial relationships
Classification encoding
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41. Comparison of conventional database and spatial database
continuous/correlation
Discontinuous
Non-correlation
Continuous
Spatial correlation
Type of entity/spatial relationship
Few
Steady
Many
Unsteady
Record length
Structured
Equal
Non-structured
Unequal
Query and manipulation
words、numbers
Spatial operations besides words and numbers
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42. Spatial database management
Hybrid model based on data file and relational database
Extended model based on relational database
Integrated model based on object-relation database
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43. Spatial data management based on file-relational database
GIS interface
Graphic process
DBMS
Graphic file
database
Attribute
Development
language
Database development
location
attribute ID
data file
database
Database
development
Graphic interface
Attribute interface
early
Graphic process
DBMS
GIS interface
Graphic file
database
Attribute
Database
development
Development
language
ODBC agreement
Graphic process
DBMS
Graphic file
database
Attribute
database
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44. Spatial data management based on relational database
Attribute data
（equal records）
GIS interface
Spatial data
（unequal records）
Relational
tables
Binary
blocks
DBMS
Spatial
database
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45. Spatial data management based on object-relation database
GIS
interface
Spatial data process
Extend entities type
DBMS
Spatial
database
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46. GIS spatial data organization
Study domain
GIS project
Concomitant
control
Spatial
index
Workspace 1
Workspace2
Workspace n
Work layer
objects
Logic layer
Arc/Info
MGE
GeoStar
Attribute
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47. Spatial data index What is spatial data index
Why is spatial data index needed in GIS
How to build spatial data index
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48. Spatial data index:object range index
Collection of spatial objects 1 2 3 4 5 6 4
Ymax
Ymin
Xmin
Xmax ID
Xmax
Xmin
Ymax
Ymin 1 … 2 3
Xmax>=XN OR Xmin<=XS OR
Ymax>=YE OR Ymin<=YW No
XE<=Xmax,Xmin<=XN AND
YW<=Ymax,Ymin<=YE
YES
Retrieved windows XN YW YE XS XN YW YE XS 2 3 6
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49. Spatial data index :index based on grid3 4 1 2
P(2,3)=1
P(2,1)=7
P(2,2)=8
Header
pointer ID P 5 6 7 10 8 9
Link pointer
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50. 作业： 简述常用空间数据结构的特点； 简述空间数据库的特征，目前空间数据是如何进行管理组织的？ 简述栅格数据的压缩编码方案
试给出格网索引实现的原理（建立和检索）
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