GIS as tool for Natural Resource Management

1. ARBA MINCH UNIVERSITY
School of Graduate Studies
College of Social Science
Department of Geography and Environmental Studies
Program: PhD in Environment and Natural Resource Management
Course: Geo-Spatial Analysis, software application and Environmental Modeling
(GeES-813)
Presentation title: Geographical Information System (GIS)
By: Zewde Alemayehu
Instructor: Dr. Vanum Govindu
Arba Minch, Ethiopia
November 2018 1

2. Presentation Content
 Introduction
 Geographic Phenomena
 Data entry and preparation
 Data types and structures
 Coordinating systems
 Projections
 Spatial referencing system & GPS
 Spatial Analysis
 Data Visualization
2

3. Introduction
Geographical Information System (GIS)
 GIS is an integrated system of computer hardware and software coupled with procedures and
a human analyst which together support the capture (collection), storing, management,
manipulation, analyzing, displaying & querying geographically related information to
solve real world problem.
 It is an organized collection of computer hardware, software, geographic data and personnel
designed to efficiently Capture, Store, Update, Manipulate, Analyze and Display all forms of
geographically referenced information
 Geographic = Spatially Referenced Data (have locations and dimensions within a
coordinate space).
 Information = Data Processed into a usable Form (extraction of specific and meaningful
information from a diverse collection of data).
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4. GIS…
 System = a framework for Manipulating, Querying, Analyzing and Disseminating
Information.
 Spatial data is any data with which position is associated.
 E.g. soil map and its data, land use/land cover map and its data, Cadastre map and its data.
 Non-spatial data is any data which cannot be explained or associated in terms of position.
 E.g. human resource and financial data of an organization.
 GIS data can be described by three data types
 Geospatial data
 Attributes data
 Metadata
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5. GIS…
 What GIS?
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6. GIS…
Data vs Information
 By data, we mean representations of the real world that is the raw recording of
measurements.
 Data is of little use unless it is transformed into information.
 Spatial Data means data that contains Positional Values.
 Geospatial data is spatial data that is Geo-referenced.
 By information, we mean data that has been interpreted by human being understanding
and knowledge.
 Geo-information is a specific type of information that involves the interpretation of spatial
data.
 We transform data into information through the use of an information system.
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7. GIS…
Questions a GIS can answer
A GIS, by linking spatial and attribute information in a flexible, integrated database,
allows the user to answer a number of questions.
ESRI (1992) noted that a GIS can answer generic types of questions.
These are (in increasing order of complexity):
 Location Where is it…?
 Condition What is it…?
 Trends What has changed since…?
 Pattern How is it distributed…?
 Modeling What if…?
 Routing: Which is the best way...?
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8. GIS…
Components of GIS
 GIS is an integration of five basic components
Procedures
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9. GIS…
 Application Areas of GIS
 Agricultural applications,
 Forestry applications,
 Rangeland applications,
 Water resources applications,
 Urban and regional planning applications,
 Wetland mapping,
 Land use/ Land cover mapping,
 Geologic and soil mapping,
 Wildlife ecology applications,
 Archaeological applications,
 Environmental assessment, monitoring and management,
 Transportation and infrastructure planning,
 Market analysis, visual impact analysis,
 Land Information System and Cadastral Application ,
 Site Selecting Analysis and many other applications etc.
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10. Geographic Phenomena
Geographic phenomena exist in real world and are the study of objects of a GIS.
Geographic phenomena exist in the real world, everything you see outside is a geographic
phenomenon.
Some of the things you do not see are also geographic phenomena like temperature.
Geographic phenomenon is something of interest that:
 can be named or described (what?)
 can be geo-referenced (where?)
 can be assigned a time (interval) at which it is/was present (when?)
Geographic phenomenon can be man-made or natural phenomenon that we are interested in.
There are two groups of geographic phenomena, fields and objects:
 A geographic field: for every point in the study area, a value can be determined. e.g.
temperature, barometric pressure, elevation, etc.
 Geographic objects: populate the study area, and are usually well distinguishable, discrete,
bounded entities. e.g. buildings, geological faults, roads, rivers, etc
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11. Geographic Phenomena…
Events that takes place in geographic space and time.
Choice for a digital representation depends on the type of phenomenon.
Can be
Artificial: building
Neutral: rivers
Mixed type: pollution
There are two groups of geographic phenomena:
 Fields
 For every point of the study area, the value can be determined.
 All changes in fields values are gradual
 E.g Elivation, Temperature
 Objects
 Well distinguishable discrete entities.
 Empty spaces in between the features.
 Study spaces grouped into mutually exclusive bounded parts. e,,g building, roads
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12. Data Entry and Preparation
 Spatial data can be obtained from various sources.
 It can be collected from scratch, using direct spatial data acquisition techniques, or
 Indirectly, by making use of existing spatial data collected by others.
GIS Data Sources
 The first step of using GIS is to provide it with data-data capture - putting the data into the
system.
 The collection and preprocessing of spatial data is an expensive and time consuming process.
 A wide variety of data sources exist for both spatial and attribute data.
 The most common general sources for spatial data are:
 Hard copy maps,
 Aerial photographs,
 Remotely sensed imagery,
 Point data samples from surveys and
 Existing digital data files.
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13. Data Collection Methods
 Primary Vs Secondary Data
 Primary data is data that you collect yourself.
 A questionnaire keyed to an address
 GPS coordinates
 Survey data
 Photographs
 Secondary data is data obtained from another source.
 There is no single method of collecting data, rather there are several, mutually compatible
methods that can be used singly or in combination.
Primary Data Capture (first-hand collection):
 Digitizing
 Scanning
 Census data
 GPS collections 13

14. Data Collection Methods...
 Aerial photographs
 Remote sensing data
Secondary Data Capture (from others):
 Published or released data (originally primary data)
 All primary data from others are secondary data
Data Preparation
 Spatial Data Preparation aims to make the required spatial data fit for use.
Spatial data preparation consists of:
 Data checks and repairs
 Spatial elements
 Associating attributes
 Rasterization /Vectorization
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15. Data types and structures
We describe geographical features by recognizing two types of data:
 Spatial data which describes location (where)
 Attribute data which specifies characteristics at that location
(what, how much, and when)
How do we represent these digitally in a GIS?
By grouping into layers based on similar characteristics (e.g hydrography, elevation, water
lines, sewer lines, grocery sales) and using either:
 vector data model (coverage in ARC/INFO, shapefile in ArcView)
 raster data model (GRID or Image in ARC/INFO & ArcView)
By selecting appropriate data properties for each layer with respect to:
 projection, scale, accuracy, and resolution
How do we incorporate into a computer application system?
By using a relational Data Base Management System (DBMS)
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16. Data types and structures…
 Vector Data Structure: Node/Arc/Polygon Topology
 Comprises 3 topological components which permit relationships between all spatial elements to
be defined (note: does not imply inclusion of attribute data)
 ARC-node topology:
 defines relations between points, by specifying which are connected to form arcs
 defines relationships between arcs (lines), by specifying which arcs are connected to form
routes and networks
 Polygon-Arc Topology
 defines polygons (areas) by specifying
which arcs comprise their boundary
 Left-Right Topology
 defines relationships between polygons (and thus all areas) by
 defining from-nodes and to-nodes, which permit
 left polygon and right polygon to be specified
 ( also left side and right side arc characteristics)
Left
Right
from
to
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17. Data types and structures…
Raster data models
Rasters can be different types of tesselations
Regular tesselations
Squares Triangles Hexagons
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18.  A coordinate system is a system designed to establish positions with respect to given
reference points. The coordinate system consists of one or more reference points, the styles of
measurement (linear or angular) from those reference points, and the directions (or axes) in
which those measurements will be taken.
Coordinating systems
In satellite navigation various coordinate
(reference) systems are used to precisely define
the satellite and user locations.
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19.  Cartesian coordinates:
 rectangular coordinate system,
 using linear distance for defining locations.
 Geographic coordinates:
 two-dimensional coordinate system,
 refer to locations on/close to the Earth’s surface,
 using angles for defining locations.
Coordinating systems…
 Latitudes/parallels (φ):
form circles on the surface of the ellipsoid.
The angle between the ellipsoidal normal through a point and the equatorial plane.
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20. Coordinating systems…
Longitudes/meridians (λ):
formellipses(meridian ellipsoid. ellipses) on the angle between the meridian ellipse which
passes through Greenwich and the meridian ellipse containing the point in question.
Working with degrees
DMS (degree, minute, second)
DD (decimal degree)
DDM (degree decimal minute)
10 = 60’
1’ = 60’’
10 = 60’ x 60’’=3600’’
DMS: 5 1 0 2 9 ’ 1 6 ’’ DD:51.4877
29 minutes = 29/60 = 0.4833 degrees 16 seconds = 16/3600= 0.0044 degrees
510 + 0.48330 + 0.00440 = 51.48770
23.2256 = 230 ?’?’’ 20

21. Map projection: a mathematically described technique to represent the Earth’s curved
surface on a flat map.
no simple way to flatten out a piece of ellipsoidal or spherical surface,
results in distortions with stretching some parts of the surface more than others.
Projections
The cylindrical, conical, and planar surfaces are all tangent surfaces;
they touch the horizontal reference surface in one point (plane) or
along a closed line (cone and cylinder) only.
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22.  If the surfaces are chosen to be secant:
The reference surface is intersected along one closed line (plane) or two closed lines
(cone and cylinder).
Projections…
 Normal projections:
the symmetry axis coincide with the rotation axis of the ellipsoid or sphere.
 Transverse projections:
 the symmetry axis is in the equator.
 Oblique projections: symmetry axis is somewhere between the rotation
axis and equator of the ellipsoid or sphere. 22

23. Properties of map Projections
Only some aspects of the representation are geometrically correct.
 maps do not exist without distortions.
 Conformal:
 shapes/angles are correctly represented (locally).
 Equivalent/equal-area:
 areas are correctly represented.
 Equidistance:
distances from 1 or 2 points or along certain lines are correctly represented.
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24.  Normal cylindrical projections:
 are typically used to map the world in its entirety.
 Conical projections:
 are often used to map the different continents.
 Normal azimuthal projection:
 may be used to map the polar areas.
 Shape of the area should be considered:
 Circular
 Rectangular
 Triangular
Azimuthal
Cylindrical
Conical
Selection of a map projection
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25. Spatial referencing system & GPS
One of the defining features of GIS is the ability to combine spatially referenced data.
A frequently occurring issue is the need to occurring issue is the need to combine spatial
data:
 from a given country with global spatial data sets,
 from different sources,
 that use different spatial reference systems.
 Toperform these kinds of tasks, GIS users need to understand basic spatial referencing concepts.
 Reference Surface
 Due to practical reasons, two types of spatial positioning are considered:
 elevations (related to a vertical datum),
 horizontal positions (related to a horizontal datum).
 Two main reference surfaces have been established to approximate the shape of the Earth.
 geoid
 ellipsoid
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26. Global Positioning System (GPS)
Initially developed by the U.S. Department of Defense for military use.
Still maintained by DOD (Department of defense) today, but can also be for civilian use.
 Navigation in your car.
 Finding your favorite fishing hole.
 Mapping trails or roads.
 Collecting data.
The GPS receiver must have 3 things to calculate distance:
1. Exact location of the satellites
2. The Speed at which the radio signal from the satellites is traveling
3. Very accurate timing to track the time it takes for the signal to go from satellite to receiver
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27. How does GPS work?
In fact, GPS relies on 24 satellites that orbit the earth in very precise paths.
Imagine that a GPS unit communicates with only one of these 24 satellites.
Then, the GPS can only make a large and general “You Are Here”.
 Communication with four satellites is
usually enough to improve location
accuracy to within about 10 meters.
 Some GPS units can provide location
within 1 meter!
 Postprocessing can provide sub-
centimeter accuracy
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28. The GPS system operates on the principles of trilateration, determining positions from
distance measurements.
This can be explained using the velocity equation.
Velocity =
Distance
Rearranging the equation for distance:
Distance = Velocity x Time
The signals from the GPS satellites travel at the
speed of light => 3x108 m/s.
How does GPS work?
Time
Components of a GPS
GPS uses three parts:
Space Segment
satellites
Control Segment
base stations
User Segment
fighter jet
surveyor
hiker 28

29. Wide Area Augmentation System (WAAS)
GPS Accuracy
Accuracy depends on:
 Quality of equipment
 Time over which observations are made.
Source Amount of Error
Satellite clocks: 1.5 to 3.6 meters
Orbital errors: < 1 meter
Ionosphere: 5.0 to 7.0 meters
Troposphere: 0.5 to 0.7 meters
Receiver noise: 0.3 to 1.5 meters
Multipath: 0.6 to 1.2 meters
Selective Availability
User error: Up to a kilometer or more
 GPS alone does not meet the FAA's navigation requirements for accuracy, integrity, and availability.
 The Federal Aviation Administration (FAA) and the Department of Transportation (DOT) are developing
the WAAS program for use in precision flight approaches. WAAS corrects for GPS signal errors caused by
ionospheric disturbances, timing, and satellite orbit errors, and it provides vital integrity information
regarding the health of each GPS satellite.
 WAAS consists of approximately 25 ground reference stations positioned across the United States that
monitor GPS satellite data.
 Two master stations, located on either coast, collect data from the reference stations and create a GPS
correction message.
 This correction accounts for GPS satellite orbit and clock drift plus signal delays caused by the atmosphere
and ionosphere.
 The corrected differential message is then broadcast through one of two geostationary satellites, or
satellites with a fixed position over the equator.
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30. Spatial Analysis
 Spatial data analysis involves manipulations or calculation of coordinates or attribute
variables with various operators (tools).
Why do we need to conduct analysis?
 In order to figure out what to do.
 To understand the problem at hand.
 To establish a solution to the problem.
 To optimize our solution.
 To guide our implementation.
 Applying the solution and knowing the effects before it is actually implemented in
the real world.
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31. Spatial Analysis…
Spatial data analysis aims to find answers to questions that have spatial relevance. Example:
 Where is the most suitable site for waste disposal?
 Which areas are not prone to landslides?
 Where is the best site for plantation of certain species?
Steps in analysis:
 Frame the question
 Select your data
 Choose analysis method
 Process the data
 Look at the results
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32. Spatial Analysis…
GIS Analysis Functions
 Measurement
 Selection queries
 Reclassification
 Dissolving
 Overlay operations
 Buffering
 Thiessen polygon
 Spread computation
 Seek computation
 Network analysis Connectivity
analysis
Neighborhood
or proximity
operations
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33. Spatial Analysis…
Reclassification
 It is an assignment of a class or value based on the attributes or geography of an object.
 It is used to reduce the complexity of a layer in order to show patterns.
 Reduce the number of classes and eliminate details.
 Two types of classifications:
 user controlled classification and
 automatic classification
User controlled classification
Classification table
Two examples of classification tables: The table on the left, the
original values are ranges, in
the table on the right the old
values already were a
classification. 33

34. Spatial Analysis…
Automatic classification:
 User specifies the number of output classes.
 Computer decides the class break points.
 Two methods of determining the class breaks will be discussed:
 Equal interval technique
 Equal frequency technique
Equal interval is calculated as:
 Where:
 Vmax is the maximum attribute value,
 Vmin is the minimum attribute value
 n is the number of classes.
In our example: (10-1) / 5 ≈ 2
Each class will have two values.
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35. Spatial Analysis…
Equal frequency, is also called quantile.
Total number of features / number of classes (n)
Create categories with roughly equal number of features
(or cells).
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36. Spatial Analysis…
Dissolve
 A function whose primary purpose is to combine like features within a data layer.
 Adjacent polygons may have identical values.
 Dissolve removes or “dissolves away” the common boundary.
 Used prior to applying area-based selection in spatial analysis.
 Dissolve is often used after reclassification.
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37. Spatial Analysis…
 Standard overlay operators take two input data layers, and assume they are:
 geo-referenced in the same system,
 overlap in study area.
 If either condition is not met, the use of an overlay operator is senseless.
 The principle of spatial overlay is to:
 compare the characteristics of the same location in both data layers,
 produce a new output value for each location.
Vector overlay techniques
 Intersection
 Clip by
 Overwrite by
Raster overlay techniques
 Arithmetic operators
 Comparison and logical operators
 Conditional expressions
 Decision table 37

38. Spatial Analysis…
Vector Overlay-Intersection
The standard operator for two layers of polygons is the
polygon intersection operator.
The result of this operator is the collection of all possible
polygon intersections
The attribute table combines the information of the two
input tables (spatial join).
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39. Spatial Analysis…
Vector Overlay-Clip
Clip takes a polygon data layer and restricts its
spatial extent (the area that it covers) to the outer
boundary of a second input layer (clip layer).
No other polygons from the clip layer play a role in
the result.
This technique can be used to reduce the area of a
thematic layer to that of the study area.
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40. Data Visualization
A Map Is:
 A representation or abstraction of geographic reality.
 A tool for representing geographic information in a way that is visual, digital or
tactile.
 A reduced and simplified representation of (parts of) the earth’s surface on a
plane.
According to the international cartographic association, a map is:
 a representation, normally to scale and on a flat medium, of a selection of material or
abstract features on, or in relation to, the surface of the Earth.
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41. Data Visualization…
Main Characteristics of Maps
i. Maps Provide Answers In Graphical Form To Questions Related To:
 Where – related to geographic location. E.g. Where did the GIS students come from?
 What – refers to geographic attributes. E.g. What is the type of land use?
 When – refers to time. E.g. When did the longest coastline occur?
 More complex, combined questions are also possible.
ii. Maps Offer Abstract Representations (Models) Of
Reality, That Are:
Simplified
Classified
Symbolized
Reality
More abstract
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42. Data Visualization…
iii. Maps Are Representations At Scale.
Scale – ratio between distance on the map corresponding distance in reality.
 Scales may be expressed as unit equivalents, representative fractions, ratios
or graphical. 1mm = 25m (Unit equivalent), or 1/25,000 (Representative
Fraction), or 1:25,000 (Ratio) Graphical/scale bar.
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43. Maps and their Use
Mapping Is A Communication Tool:
Convey a message to a public through a medium.
Some forms of communication are better than others.
All maps are not equal, even if some are representing the same features.
 Cartographic quality.
 Maps are using visual communication tools.
43

44. Maps and their Use…
Recording And Storing Information:
Enterprises and institutions are using maps to store large amounts of information,
Location of resources,
Location of people,
Parcels,
Property,
Infrastructure,
Utilities,
Etc…
44

45. Maps and their Use…
Analyzing Distributions and Patterns:
 Maps can be used to analyze spatial distributions.
 Visualization helps conceptualization of patterns and processes.
45

46. Maps and their Use…
Presenting And Communicating:
 Express concepts and ideas that are verbally difficult and complex to portray,
 Demonstrate,
 Convince,
 Persuade,
 Inform/Misinform.
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47. Mapping and efficiency
 Cartography
 Science / art / technique of map production.
 Uses a set of defined graphical elements to communicate a message.
 Graphical Elements Specific To Cartography
 Coordinate systems,
 Map projections,
 Scale,
 Symbolism.
 Legend
 Explaining the meaning of graphical symbols.
 With the large diffusion of maps, some symbols do not require explanation anymore.
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48. Mapping and efficiency…
 Designing A Good Map
 A good map conveys well its intended message.
 What Is The Goal Of The Map?
 What the reader should gain from the map or how the reader should respond.
 Motives vary greatly.
 Convey accurate information about spatial relationships.
 Sway public debate.
 The motive will have a great bearing on the content of the map (the information included) and
its form (the cartographic strategies employed).
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49. Mapping and efficiency…
Symbolic Abstraction
 Encoding real-world geographic features.
 How to symbolize?
Who Is The Reader?
 Map design is not the same according to the intended public.
 Identify the type of reader being addressed.
 Important to have an idea about what the audience is likely to know about the subject matter
of the map.
 Map literacy:
 How much background the readers have in using maps.
 Background in cartography and for use in a public debate.
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50. Mapping and efficiency…
Where It Will Be Used?
 Usage depend on the type of medium the map will be published in (book, magazine, news,
web site, etc.).
 Some maps are used only once and then discarded.
 Others are intended to used for reference for decades or centuries.
What Data Is Available?
 Some maps use reliable sources while others have sketchy information.
 Decisions about map design are tempered greatly by source materials themselves.
What Resources And Equipment Are Available?
 Underline the time and the costs for map production.
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