Semi-structured Data and XML in Geographic Data Modeling and...
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Geographic Representation Models Emmanuel Stefanakis http://www2.unb.ca/~estef/ Stefanakis, E., 2014. Geographic Databases and Information Systems. CreateSpace Independent Publ. [In English], pp.386. Get a copy from Amazon Chapter 9
Transcript of Semi-structured Data and XML in Geographic Data Modeling and...
Geographic Representation Models
Emmanuel Stefanakis
http://www2.unb.ca/~estef/
Stefanakis, E., 2014. Geographic Databases and Information Systems.
CreateSpace Independent Publ. [In English], pp.386.
Get a copy from Amazon
Chapter 9
2
Models…
• Representation of Reality…
Reality Image of Reality
(human perception)
Representation
on a Computer
(implementation)
Representation
model
Data
model
3
Representation Models
• Objectives…
– should answer two questions…
• what is present?
• where is it located?
What?
Where?
4
Representation Models
• Models…
– two approaches…
• space as a set of discrete entities
• space as a continuous field
?
?
?
What?
Where?
5
Representation Models
• Model 1…
– space as a set of discrete entities
• entities should be…
– identifiable
– relevant to the application
– with sharp boundaries
– describable (with attributes)
6
Representation Models
• Model 1…
– space as a set of discrete entities
• in 2D static space …
– entities are represented by…
» points
» lines
» polygons
– based on an orthogonal or map projection in a 2D
plane surface
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Representation Models
• Model 2…
– space as a continuous field
• each location of the field …
– is assigned one value for
an attribute of interest
» elevation
» vegetation
» temperature
» humidity
?
?
?
8
Representation Models
• Model 2…
– space as a continuous field
• fields are characterized by
– what is changing
» e.g., elevation
– how smoothly it changes
» e.g., steep slope
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Representation Models
• Thematic layers …
– space is split into sub-spaces
• each sub-space corresponds
to a theme (thematic
dimension)
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Representation Models
• Tomlin’s Model…
– geographic data forms a hierarchy
map
thematic
layer 1
thematic
layer 2
thematic
layer 3
zone 1 zone 2 zone 3
location 1 location 2 location 3
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Representation Models
• Tomlin’s Model…
– can represent both discrete entities and continuous fields...
map
thematic
layer 1
thematic
layer 2
thematic
layer 3
zone 1 zone 2 zone 3
location 1 location 2 location 3
Continuous fields
Discrete entities
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Representation Models
• Tomlin’s Model…
– In a dynamic world …
map
thematic
layer 1
thematic
layer 2
thematic
layer 3
zone 1 zone 2 zone 3
location 1 location 2 location 3
Space-time cubes (2+1D modeling
space)
Space-time locations
Άνδρος
Μύκονος
Τήνος
Δήλος
Ρήνεια Σύρος
Γυάρος
Κέα
Κύθνος
0h 00
min
0h 10
min
0h 20
min
0h 30
min
0h 40
min
0h 50
min
1h 00
min
1h 10
min
Sailing in the
Aegean Sea
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Representation Models
• Tomlin’s Model…
– In a dynamic world …
X
Y
T
Dec. 22, 2001
23:59
individual location
Dec. 22, 2001 00:00
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Representation Models
• Tomlin’s Model…
– In a fuzzy dynamic world …
Map
Thematic
Layer 1
Thematic
Layer 2
Thematic
Layer k
Lexical
Layer 1
Lexical
Layer 2
Lexical
Layer j
Zone 1 Zone 2 Zone i
…
…
…
location 1 location 2 location n…
X
Y
T
1901
2000
GREECE
Crete individual location
vegetation
layer
dry-land: 0.2
vineyard: 0
orchard: 0
forest: 0.7
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Representation Models
• We should be able to represent …
– Spatial Entities + Spatial Relations
A D
E
C
B
G
F
Company ltdY
X
N
Entities?
Relations?
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Representation Models
• Spatial relations…
– they come from …
• the relative positions of geographic entities in space
– most common …
• topological relations
– neighbor, overlap, etc.
• order relations (direction relations)
– in_front_of, north_of, etc.
• metric relations (distance relations)
– near, far, etc.
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Representation Models
• Topological relations…
– topology …
• studies the geometric relations of objects that
are preserved under any …
– translation,
– rotation or (topological transformations)
– scale change
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Representation Models
• Topological relations…
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Representation Models
• Topological relations…
– a model for representing them …
• for two entities A, B
– BA, BB the border lines
– IA, IB the interior areas
• check the four intersections
BA BB IA IB IA BB BA IB
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Representation Models
• Topological relations… (Egenhofer’s relations)
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Representation Models
• Topological relations…
– A 3x3 (or 9) intersection matrix …
• specifies the topological relationship
• e.g., A TOUCH B
A B
B
b i e
b 1 0 1
A i 0 0 1
e 1 1 1
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Representation Models
• Temporal relations… (Allen’s relations)
Temporal relation Definition
Α before Βt
AA B
AB
t
A B
t
A B
t
B
A
t
A
B
t
AB
t
Α equal to Β
Α meets Β
Α during Β
Α overlaps Β
Α ends Β
Α starts Β
Geographic Representation Models
Emmanuel Stefanakis
http://www2.unb.ca/~estef/
Stefanakis, E., 2014. Geographic Databases and Information Systems.
CreateSpace Independent Publ. [In English], pp.386.
Get a copy from Amazon
Chapter 9
