What is GIS?

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GIS and Arcview
Introductory notes
Raquib Ahmed
Institute of Environmental Science
[email protected]
What is GIS?
• A technology
– hardware & software tools
• An information handling strategy
• The objective: to improve overall decision
making
GIS: a formal definition
“A system for capturing, storing, checking,
integrating, manipulating, analysing and
displaying data which are spatially
referenced to the Earth. This is normally
considered to involve a spatially referenced
computer database and appropriate
applications software”
GIS definition
“… a special case of information system where the
database consists of observation son spatially distributed
features, activities or events, which are definable in
space as points, lines or area. A geographic information
systems manipulates data about these points, lines and
areas to retrieve data for ad hoc queries and analyses”
Why is GIS unique?
• GIS handles SPATIAL information
– Information referenced by its location in space
• GIS makes connections between activities
based on spatial proximity
GIS: historical background
This technology has developed from:
– Digital cartography and CAD
– Data Base Management Systems
ID
1
2
3
1
2
X,Y
ID ATTRIB
1
2
3
3
CAD System
Data Base Management System
Digital
Mapping
Computer
Aided
Design
Photogrammetry
GIS
Databases
Surveying
Remote
Sensing
Cross-disciplinary nature of GIS
GIS components
Spatial
data
GIS
Computer hardware /
software tools
Specific applications /
decision making objectives
What makes data spatial?
Grid co-ordinate
Placename
Latitude / Longitude
Postcode
Description
Distance & bearing
Characteristics of spatial data
• Location
•
•
•
•
•
•
Description:
Post Code:
Grid Reference:
Latitude/Longitude:
Elevation:
Elepsoid:
Rajshahi University, IES
6205
518106.72 168530.37
28.38°E, 88.55°N
17.500m (MSL)
WGS84
Characteristics of spatial data
Geometry
• The shape of a
building or county
• The course of a river,
the route of a road
• The shape of the
landscape, relief
Characteristics of spatial data
• Topology




Connected to
Within
Adjacent to
North of . . .




Within the Royal Borough of Kingston-upon-Thames
Opposite the Surrey County Council building
North of Surbiton station
Adjacent to Penrhyn Road
Spatial Data: examples
• Socio-economic data
– Regional health data
– Consumer / lifestyle profiles
– Geodemographics
• Environmental data
– Topographic data
– Thematic data, soils, geology
Spatial data storage
7,10
• Vector model
5,9
10
9,8
4,7
polygon
8,6
1,6
2,5
5
6,6
line
point
5,4
2,2
4,1
5
• Raster model
as geometric objects:
points, lines, polygons
10
as image files
composed of grid-cells
(pixels)
• Date type
– Integer
– Real
– Byte
• File type
– ASCII
– Binary
– Packed Binary
Spatial data storage model
• important in determining the potential applications of the system
• model may also affect the type of analysis work that can be
achieved
• hybrid approach to storing graphical and attribute information
• Attribute information often stored within standard relational
database
• Graphical information is stored in a proprietary file system
– optimised tools for data handling
– although non-standard proprietary system will be difficult to
integrate with other systems, it will tend to be very efficient at
handling large graphics files.
Vector data model
• advantage of the vector data format: allows precise representation of
points, boundaries, and linear features.
– useful for analysis tasks that require accurate positioning,
– for defining spatial relationship (ie the connectivity and adjacency)
between coverage features (topology), important for such purposes as
network analysis (for example to find an optimal path between two nodes
in a complex transport network)
• main disadvantage of vector data is that the boundaries of the resulting
map polygons are discrete (enclosed by well-defined boundary lines),
whereas in reality the map polygons may represent continuous
gradation or gradual change, as in soil maps.
Raster data model
• good for representing indistinct boundaries
– thematic information on soil types, soil moisture, vegetation, ground
temperatures
• as reconnaissance satellites and aerial surveys use raster-based
scanners, the information (ie scanned images) can be directly
incorporated into GIS
• the higher the grid resolution, the larger the data file is going to be
Modelling the real world
y
1 1 20 50
1 2 24 45
1 3 52 55
x
2 1 0 45 46
40
...
000000020
000001000
020010000
000020000
2 2 2 0 1 ...
Vector data
Land use parcels
Raster data
Manipulation and analysis
• What would happen if . . .
A chemical leaked into a river?
• Where does . . .
The Green Belt exist in relation to the City?
• Has . . .
Population changed over the last ten years?
• Is there a spatial pattern related to . . .
Car ownership in our area?
Databases & GIS
Spatial data
• At a simple level a
GIS may just form
the graphical
interface to a
database
• The majority of GIS
applications follow
this example
MapInfo
Linked database table
SQL Query Manager
Geo-relational Data Models
• Linked tables based on the relational model,
but storing geographical information such as:
– Geometry
– Topology
– Attributes
GIS & Analysis
In the context of GIS, analysis is...
“Deriving new information from existing data”
It is also the manipulation of data to solve a problem
e.g. identify all areas within 500m of a lake
Increasing use is made of the analytical capabilities of GIS, BUT
many GIS projects only use the software to store and manage
geographical data
Yet analysis often relies on many simple basic GIS techniques
Simple Query
• The identification of objects and their attributes
either by location or attribute query.
Buffering
• Creation of an area of interest around an object
– proximity analysis and environmental impact assessment.
Overlays
• Layer: A thematic plane of GIS features containing
geographically and logically related data
• Overlaying involves superimposing two or more map layers to produce
a new map layer.
•
Example: a new genetically engineered variety of wheat grows well in dry
environments, with long growing seasons and alkaline soils. Given the
availability of data on the length of the growing season, moisture regime and
soil alkalinity, where is the best place to plant the wheat?
– overlaying (superimposing) several maps showing (separately) water-budget,
growing season length, soil pH, sodium content, and so on. The GIS analysis can
establish the locations where all the favorable soil conditions coincide, as the places
where the wheat will grow best.
Country boundary
Plus district boundary
Plus major rivers
Plus major roads
Plus railway lines
Plus domestic air routes
Plus district towns
More functions?
•
•
•
•
•
•
•
Unioning
Distance measuring
3D modeling
Vertical and horizontal scaleability
Web based operation
Data center based operation
More ……
The benefits of GIS include:
• Better information management
• Higher quality analysis
• Ability to carry out “what if?” scenarios
• Improve project efficiency
GIS Applications
•
•
•
•
•
•
Facilities management
Marketing and retailing
Environmental
Transport/vehicle routing
Health
Insurance
and many more . . .
Coastal bathymetric measurement
Blue
NIR
Finding the best route to evacuate
people during cyclone – A GIS
application
Important features of cyclone in
Bangladesh
• In last 30 years, nearly 9,00,000 people died
due to disastrous cyclones in Bangladesh
• Six out of nine depressions formed in the
Bay of Bengal normally cross the coastal
belt of Bangladesh almost every year
• Thousands of people lose employment due
to cyclones
• Cyclone preparedness can reduce the loss of
life and property
Necessity of the study
• The coastal region of Bangladesh is densely
populated, so risk is higher
• The forecasting system in Bangladesh is not so
advanced
• Can be a part of well organized pre, in time and
post cyclone management program
• Proposing a new road network for the coastal
regions
• Overall saving the human lives
Statement of the problem
• Sudden evacuation of people creates a lot of
pressure on existing road network
• The travel path should be the shortest
• Information regarding the cyclone should be upto-date (mainly regarding the track)
• The people don’t have a lot of alternatives to
choose from
• Coastal region of Bangladesh is crisscrossed by
lots of rivers and small canals
General statistics of cyclone in Bangladesh
Month wise Distribution of the Frequency of cyclones
along Different parts of the coast of Bangladesh
Month
January
February
March
April
May
June
July
August
September
October
November
December
Total
Khuln
Sundarban
coast
0
0
0
0
1
1
0
0
4
5
1
1
13
BarisalPatuakhali
Noakhali
coast
0
0
0
0
3
2
0
0
0
5
2
2
14
Noakhali
Chittagong
coast
0
0
0
1
11
5
0
0
2
8
6
0
33
Chittagong
Cox's Bazaar
coast
0
0
0
3
6
1
0
0
0
5
4
3
22
Total
Frequency
0
0
0
4
21
9
0
0
6
23
13
6
82
Frequency
0
0
0
4.88
25.61
10.98
0
0
7.32
28.05
15.85
7.32
100.00
CLASSIFICATION OF CYCLONE
DISTURBANCES IN THE BAY OF BENGAL
 The cyclonic disturbances over the North Indian Ocean as
defined in the WMO Tropical Cyclone Operational Plan for
the region (TCP-21) are as follows:
Types of Disturbances
Low
Depression
Cyclonic storm
Severe Cyclonic Storm
Severe Cyclonic storm
of hurricane intensity
 In Bangladesh the terms well marked low and
deep depression are also used to indicate
cyclonic disturbances with wind speed between
17-21 kt (31-40 kph) and 27-33 (51-61 kph)
respectively. The Nomenclature of the Tropical
disturbances have been changed in the 26th
Session of WMO/ESCAP Panel on Tropical
cyclone meeting held in Maldives during
February, 1999 as follows:
Corresponding
Knots
< 17 kt
17-33 kt
34-47 kt
48-63 kt
64 kt
Wind speed ranges
Kts
Kph
>17
17-27
28-33
34-47
48-63
64-119
>120
>31
31-50
51-61
62-88
89-117
118-220
>221
Wind Speed Kph
< 31 km
31-61 km
62-88 km
89-117 km
>118 km
Nomenclature
Low Pressure Area
Depression
Deep Depression
Cyclonic Storm
Severe Cyclonic Storm
Very Severe Cyclonic Storm
Super Cyclonic Storm
Track of important
cyclones in Bangladesh
Existing road
network of kala
Para Thana
Roads
Extracted road network from 15m resolution
ETM+ panchromatic image
Roads
Land use of Kala para thana
General land use
Area under settlement
Settlement
Extracted road
network and
settlements
Settlement
Roads
Location of
cyclone shelters
10 km service
area of cyclone
shelters
Service area
Settlement
Roads
Settlement areas
out of 10 km
service area
Service area analysis results
• There are still some settlement areas which are out
of 10km service area
• As most of the roads are not metalled so it is
difficult to count the probable time to reach the
shelters from home
• Moreover there are lots of rivers which also work
as a barrier and lengthen the total time of traveling
• Here my suggestion is to build at least a new
cyclone shelter in the north western portion so that
most of the people could be brought under 10km
service area facilities
Best route for the people from the surrounding
settlement areas who will come to Nilganj cyclone
shelter
Best route for the people from the surrounding
settlement areas who will come to Lata Chapali
cyclone shelter
Best route for the people from the surrounding
settlement areas who will come to Mithaganj
cyclone shelter
Best route for the people from the surrounding
settlement areas who will come to Dhankhali
cyclone shelter
Arsenic Poisoning- Health Risk & Mitigation
Arsenic
Arsenic is a highly toxic, naturally occurring grayish- white
element used as a poison in pesticides and herbicides.
Chemical and Physical Properties
Atomic Number
33
Atomic Weight
74.9
Specific Gravity
5.73
Melting Point
817°C at 28atm
Boiling Point
613°C (sublimes)
Vapour Pressure
1mm Hg at 372°C
Sources of occupational exposures to
• Arsenic
Mining and processing
•
•
•
•
•
•
•
Wood Preservation
Herbicide
Pesticide
Glass making
Hide preservation
Food additive:
Laboratory procedures
Arsenicosis
or
Arsenic
Toxicity
• Diffuse Melanosis (First Stage)
• Keratosis (Middle Stage)
• Cirrhosis ( Third Stage)
Arsenic Symptoms
Usually it is found that the affects of arsenic
pollution become visible on the skin after
8-14 years of taking arsenic contaminated
water regularly.
· Darkening of skin (Diffuse Melanosis)
· Spotted pigmentation (spotted melanosis)
· Leucomelanosis (white and black spots side
by side
· Buccal mucus membrane melanosis (diffuse,
patchy, or spotted mela-nosis)
· Conjunctival congestion and nonpitting
swelling (solid edema) of the feet.
· Squamous cell carcinoma
Amount of Arsenic
in Tube-Well Water
Arsenic Concentration on Food
•
•
•
•
•
•
•
•
•
Arum- 150mg/Kg.
Bean- 5.1 mg/Kg
Tomato- 20.1 mg/Kg
Papaya- 0.83 mg/Kg-1.1 mg/Kg
Cauliflower- 1.8 to 2.7 mg/Kg
Cabbage 0.05 to 7.2 mg/Kg
Leafy Vegetables- 1.9 to 4.5 mg/Kg
Wheat- 1 mg/Kg
Rice 5.3 mg/Kg
Litho logy of the
sample Tube-Well
Locations
Geology of the Sample Tube-Well Locations
Study Area
Extraction
As the greatest values of
arsenic has been observed in
Chadpur and Luxmipur
districts so these two districts
have been selected as study
area
Study Area
Amount of Arsenic in the
Tube-Well water in Study
Area
Arsenic GRID Map of
the Study Area
Relationship Between Well
Depth and Arsenic
Concentration
Salinity in the soil of
the Study Area
Salinity in MMHOS/cm
Surface Generated Using
Arsenic values
Relation between
Soil Salinity and
Arsenic
Here the value of regression
is -0.1165. Which means
that there is no relationship
between these two variables
Study Area Extraction from the Satellite Images
Image of Study Area With
Sample Tube-Well
Locations
FCC Image of the
Study Area
The FCC image has been used to
Extract the water bodies of the
Study area.
Water Bodies of the
Study Area
Here the dots represents water bodies.
Which plays an important role in the
ground water recharge
Some Suggestions for
Arsenic Prevention
• Minimizing the use of ground water sources
for irrigation and water supply purposes
• Using surface water
• Controlling the use of pesticides and
fertilizer containing arsenic more than the
danger level
• Ground water management through
recharging ground water reservoirs
Environmental assessment
Outline:
– Introduction
– Multi-criteria evaluation (MCE)
– Examples
Introduction
• Principles of environmental protection
– land/air/water as common resource
– limited: scale and sustainability
– essential to make best possible use
• identify suitability/appropriateness of use
• prevent overuse and degradation
• “protect and survive” principle
– requires legislation (e.g. EPA, 1990; T&CPA,
1990)
Question…
• How does one develop an Environmental
Assessment using GIS?
GIS-based EA
• Key stages:
–
–
–
–
–
–
problem definition
method of impact assessment
data collection and processing
assessment
evaluation
reporting
Example: wind farms
Example: wind farms
• Problem?
– what impacts?
• Method?
– what GIS analysis?
• Data?
– what data and processing required?
• Assessment?
– application of method(s)?
• Evaluation?
• Report?
GIS approaches
• Sieve mapping using:
– polygon overlay (Boolean logic)
– cartographic modelling
– Example uses:
•
•
•
•
nuclear waste disposal site location
highway routing
land suitability mapping (e.g. wind farm location)
etc.
Multi-criteria evaluation
• Basic MCE theory:
– “Investigate a number of choice possibilities in
the light of multiple criteria and conflicting
objectives” (Voogd, 1983)
– generate rankings of choice alternatives
• simple linear programming algorithms
• multi-objective optimisation
• multi-dimensionality of planning problems
Principles of MCE
• Methodology
– construct evaluation matrix…
S11…..SI1
S =
.
.
S1J…..SIJ
– standardisation (normalisation) of criterion
scores
– evaluation of matrix using MCE algorithms
MCE techniques
• Many techniques
– most developed for evaluating small matrices
– suitability for large (GIS) matrices?
• layers = criterion scores
• cells or polygons = choice alternatives
– incorporation of levels of importance (weights)
– Incorporation of constraint maps
– e.g. ideal point analysis, weighted linear
summation, hierarchical optimisation, etc.
Example: weighted linear summation
Map 1
Map 2
Map 3
Standardise
User
weights
Evaluation
matrix
MCE routine
Output
Map 4
Conclusions
• Few GIS packages provide MCE
functionality (e.g. Idrisi32)
• Most GIS provide facilities for building
MCE analyses (e.g. Arc/Info GRID)
• Important method for:
– site and route selection
– land suitability modelling
Thanks
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