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Geographic Data Analysis
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 11
2
Geographic Information Systems
• Information System
User
Interface
Data
Analyzer
Data Manager
Database Data resides
here
Management operations
(insert,delete,update,
retrieve)
Analysis
operations
(application
dependent)
3
Representation of Geographic Data
• 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
4
Representation of Geographic Data
• Tomlin’s Model…
– represents 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
(raster)
Discrete entities
(vector)
5
Geographic Operations
• An operation …
– based on Tomlin’s model
Operation
6
Geographic Operations
• Classification of operations …
– based on Tomlin’s model
Local operations Focal operations Zonal operations
7
Geographic Operations
• Local operations …
compute a new value for
each location on a layer
as a function of existing
data explicitly
associated with that
location
8
Geographic Operations
• Local operations …
Classification
23 25 33 28
25 32 34 29
34 31 32 29
29 37 28 27
0 0 1 0
0 1 1 0
1 1 1 0
0 1 0 0
value > 30
e.g., temperature
9
Geographic Operations
• Local operations …
Overlay
3 5 3 8
5 2 4 9
4 1 2 9
9 7 8 7
5 7 6 10
7 5 7 11
7 4 5 11
11 10 10 9
+
2 2 3 2
2 3 3 2
3 3 3 2
2 3 2 2
e.g.,
anglophones+francophones
10
Geographic Operations
• Focal operations …
compute new values
for every location as a
function of its
neighborhood
11
Geographic Operations
• Focal operations …
Sum of
direct neighbors
(dynamic
neighborhood)
2 1 1 2
2 3 3 3
1 4 4 2
3 1 4 2
5 7 7 6
8 13 14 10
10 13 17 11
5 12 11 8
e.g., slope or aspect
12
Geographic Operations
• Focal operations …
Direction to
direct neighbors
(static
neighborhood)
0 0 0 0
0 0 0 0
0 1 1 0
0 0 0 0
8 1 1 2
8 1 1 2
7 0 0 3
6 5 5 4
e.g., direction relation
1 2
3
4 5 6
7
8
13
Geographic Operations
• Zonal operations …
compute a new value
for each location as a
function of existing
values associated with a
zone containing that
location
14
Geographic Operations
• Zonal operations …
Search
e.g., forests (F) in NB
F L L L
F F F F
L L F F
L L F L
0 0 0 0
0 0 0 0
0 0 1 1
0 0 1 0
AND
Q Q Q Q
Q Q Q Q
Q Q NB NB
Q Q NB NB
15
Geographic Operations
16
Example…
• The problem…
– find …
• best location(s) for residential housing development…
– Constraints and opportunities
• Free land (no development)
• Dry land
• Level and Smooth land (slope < 10%)
• Close to existing roads
• South slope
• Adequate size (>1.5 km2)
17
Example…
• Input layers
– Hypsography
– Development
– Humidity
18
Example…
(1) Find vacant areas…
development
Local
classification
development
classes
Local
generalization
vacant &
developed
Zonal
search (dummy) vacant areas
19
Example…
(2) Find dry areas…
moisture
Local
classification
moisture
classes
Local
generalization
dry &
wet
Zonal
search (dummy) dry areas
20
Example…
(3) Find level areas…
hypsography
Focal
surfacial slope
Local
classification
slope
classes
Local
generalization
level &
steep
Zonal
search (dummy)level areas
21
Example…
(4) Find south-facing areas…
hypsography
Focal
surfacial aspect
Local
classification
aspect
classes
Local
generalization
south &
north
Zonal
search (dummy)south areas
22
Example…
(5) Find accessible areas (road net)…
development
Zonal
search (dummy) roads
Focal
neighborhood
road
proximity
Local
classification
road proximity
classes
Local
generalization
accessible &
inaccessible
Zonal
search (dummy) accessible areas
23
Example…
(6) Highlight the ‘good’ sites…
vacant areas
vac., dry, level,
access., south
Local
overlaydry areas
level areas
south areas
accessible areas
Zonal
search (dummy)
good sites
24
Example…
(7) The Solution …
good sites
Zonal
measurement
good sites
size
Local
classification
candidate
sites
Geographic Data Analysis
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 11
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