GIs

1. COURSE: GIS&RS
UNIT ONE:
INTRODUCTION TO GIS:
1

2. GIS refers to three integrated parts.
1. Geographic: The geographical location of the real world
(coordinate system).
Implies an interest in the spatial identity or locality of certain
entities on, under or above the surface of the earth.
2. Information: The database.
Implies the need to be informed in order to make decisions. Data
or raw facts are interpreted to create information that is useful
for decision-making.
2

3. 3. Systems: The hardware and software;
Implies the need for staff, computer hardware
and procedures, which can produce
the information required for decision-making
that is data collection, processing, and
presentation.
3

4. GIS description
There are different definitions for Geographic Information System,
each developed from a different perspective or disciplinary origin.
Some focus on the map connection, some stress the database or the
software tool kit and others emphasis applications such as decision
support.
Defining a GIS can be done by either explaining what it can do
(Functions) or by looking at the components.
Both are important to really understand a GIS and use it optimally.
4

5. GIS is defined as a computerized system for capture, storage,
retrieval, analysis and display of spatial data describing the land
attributes and environmental features for a given geographic
region, by using modem information technology (Thurgood, 1995).
 According to this definition, a GIS includes not only computing
capability and data, but also managers and users, the
organization in which they function and institutional
relationships that govern their management and use of
information.
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6. A GIS can be defined as a computing application capable of
creating, storing, manipulating, visualizing, and analyzing
geographic information.
It finds its strongest applications in;
 resources management,
 utilities management,
 telecommunications,
 urban and regional planning,
 vehicle routing and parcel delivery, and
in all of the sciences that deal with the surface of the Earth.
6

7.  GIS is defined as a decision support system involving the
integration of spatially referenced data in a problem-solving
environment. (Cowen, 1988)
 GIS is an institutional entity, reflecting an organizational
structure that integrates technology with a database, expertise,
and continuing financial support over time (Carter, 1989)
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8. Applications of (GIS)
Applications of the GIS are;
Navigation
Agriculture
Forest
Climate
Land Degradation
Water Resource etc
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9. Navigation (Routing and Scheduling):
ArcGIS supports safe navigation system and provides accurate
topographic and hydrographic data.
 Recently, s Coastal Resources Division began the task of
locating, documenting, and cataloging these no historic wrecks
with GIS.
This division is providing public information that makes citizens
awareness of these vessel locations through web map.
The web map will be regularly updated to keep the boating public
informed of these coastal hazards to minimize risk of collision and
injury. 9

10. Worldwide Earthquake Information System:
One of the most frightening and destructive phenomena of nature is
the occurrence of an earthquake.
There is a need to have knowledge regarding the trends in
earthquake occurrence worldwide.
 A GIS based user interface system for querying on earthquake
catalogue will be of great help to the earthquake engineers and
seismologists in understanding the behavior pattern of
earthquake in spatial and temporal domain.
10

11. River Crossing Site Selection for Bridges:
The important geotechnical consideration is the stability of slope
leading down to and up from the water crossing.
 It is advisable to collect historical data on erosion and
sedimentation. On the basis of these information asses the amount
of river channel contraction, degree of curvature of river bend,
nature of bed and bank.
 materials including the flood flow and the flow depth, all these
can be done in GIS within estimated time and accurately.
This information has been often used for river crossing site selection
for bridges. 11

12. Wastewater Management:
integrated planning system including sewers, catch basins, ditches, and
waterways for planning storm impacts.
❖ Air Emissions: Modeling and display of dispersal and risk from air toxics
on regions surrounding industrial facilities.
❖ Hazard Analysis: Linking drawings and databases to conduct hazardous
operations analysis for chemical operations.
❖ Forestry Management: Imaging and digital elevation modeling to evaluate
damage to forests from the effects of fire, logging, pesticides, and acid rain and to
describe trends in forest resources.
❖ Population Planning: Spatial distribution and mapping overpopulation and
slums in under developed countries using satellite imagery.
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13. Agricultural purposes: In sectors such as agriculture, GIS is used
to assess yields and management strategies.
❖ Social purposes: In social investigations, GIS is used to help
analyze spatially varying attributes of the population such as
income, crime, health or the quality of housing.
❖ Environmental uses: GIS is used in a wide range of practical
environmental issues from global warming and sea level rise to
erosion, flooding and soil, air and water pollution.
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14. What Can a GIS Do?
/GIS Architecture/Work Flow
A GIS performs six fundamental operations that make it a useful tool for
finding solutions to real-world problems.
1. Capture data:
You can add data from many sources to a GIS, and you can also create
your own data from scratch.
2. Store data:
You can store and manage information about the real world in ways that
makes sense for your application.
3. Query data:
You can ask complex questions about features based on their attributes
or their location and get quick results. 14

15. 4. Analyze data:
You can integrate multiple datasets to find features that meet specific
criteria and create information useful for problem solving.
5. Display data:
You can display features based on their attributes, a powerful feature
you’ll come to appreciate.
6. Present data:
You can create and distribute high-quality maps, graphs, and reports to
present your analysis results in a compelling way to your audience.
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16. Fig GIS workflow diagram
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17. GIS have mainly 5 components: Hardware, Software, Data, People,
and Methods.
Hardware:
Hardware is the computer on which a GIS operates; Hardware
relates to device used by end users such as graphic devices or
plotters and scanners.
 It consists of the computer system on which the GIS software will
run.
The choice of hardware system range from 300MHz Personal
Computers to Super Computers having capability in Tera FLOPS.
GIS Infrastructure
17

18. Software:
GIS software provides the functions and tools needed to store,
analyze and display geographic information.
Key software components are;
• Tools for the input and manipulation of geographic information.
• A database management system (DBMS)
• Tools that support geographic query, analysis and visualization.
• A geographical user interface (GUI) for easy access to tools.
18

19. GIS software in use are ArcGIS, MapInfo, Global mapper,
AutoCAD Map, etc.
The software available can be said to be application specific.
When the low cost GIS work is to be carried out desktop Global
mapper, and Mapinfo is the suitable option. It is easy to use and
supports many GIS feature.
 If the user intends to carry out extensive analysis on GIS
including modelling and report generation, ArcGIS is the
preferred option.
 For the people using AutoCAD and willing to step into GIS,
AutoCAD Map is a good option.
19

20. Data:
Data is one of the most important, and often most expensive,
components of a GIS.
Geographic data and related tabular data can be collected in-house or
purchased from a commercial data provider, from several websites
 A GIS will integrate spatial data with other data resources and can
even use a DBMS, used by most organizations to organize and
maintain their data, to manage spatial data.
20

21. User/People: GIS technology is of limited value without the people
who manage the system and develop plans for applying it to real-
world problems.
 The GIS users range from technical specialists who design and
maintain the system to those who use it to help them perform their
everyday work.
In other way, The term "user" may refer to any individual who will
use GIS to support project or program goals, or to an entire
organization that will employ GIS in support of its overall mission.
21

22. Methods: A successful GIS operates according to a well-designed
plan and business rules, which are the models and operating
practices unique to each organization.
In general, Geographic Information System- The organized activity
by which people;
 Measure aspects of geographic phenomena and processes.
 Represent these measurements, usually in the form of a computer
database, to emphasize spatial themes, entities and relationships.
 Operate upon these representations to produce more
measurements and to discover new relationships by integrating
disparate sources.
 Transform these representations to conform to other frameworks
of entities and relationships.
22

23. Project work
Select area of interest based on administration boundary or
watershed, and map Groundwater Potential Zone using Remote
Sensing and GIS. Project should include; introduction, objectives,
method and result.
Submission date: 15/03/23
To: E-mail; bayisajs2017@gmail.com
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24. 24
2. BASIC GIS DATA TYPES
2.1 Data Vs Information
• Data is a collection of raw facts that represent features or
details about peoples, objects, places, ideas or events
 Information is a collection of meaningful facts and figures
that can be used as basis for guidance and decision making.

25.  Data in a GIS represent a simplified view of physical
entities or phenomena
 Each entity is represented by a spatial feature or
cartographic object in the GIS, and there is an entity-
object correspondence.
Unlike other kinds of data handled routinely by modern
information systems, GIS data are complicated by the
fact that they must include information about
Position
Possible topological relations and
Attribute of the objects recorded
2.2 GIS Data
25

26.  GIS handles 2 basic data types:
Geographic (spatial) and attribute (statistical) data.
A) Spatial Data
Describes the location, shape and the possible topological
relations among each of the feature.
Spatial objects in the real world occurs in 4 easily
identifiable types:
Points, lines, areas and surfaces

26

27. Characteristics of spatial data
➲ “mappable” characteristics:
o Location (coordinate system)
o Size is calculated by the amount (length, area,
perimeter) of the data
o Shape is defined as shape (point, line, area) of
the feature
➲ Spatial relationships
Discrete or continuous
 Points
 Lines
 Areas
 Networks
• Road network
• River network
• Sewage network
Discrete features Continuous Surfaces
• Elevation surface
• Temperature surface
27

28. (i) Point Features
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These involve features having specific location without any
extension in any direction. Such features can be
represented by points in the GIS environment. Points are
represented by pair of x, y coordinates with label name.
Ex. Location of oil wells, rain gauge stations, electrical poles,
boreholes, epicenter of an earth quake, towns, etc
(a) Discrete Features

29. (ii) Linear features:
29
represents features with linear extensions.
Lines consist of series of X, Y coordinates with
starting and ending points and a label name.
Such feature has length attributes.
Features as roads, rivers, pipelines, power lines,
elevation contours are examples of such features.

30. (iii) Areas or polygon features:
30
involves features with extended areas.
They are represented by closed features designated by
a set of linked lines called polygons.
Polygons will have starting and same closed coordinate
(X,Y) and a label.
Polygons will have area and perimeter attributes.

31. (b) Continuous Surfaces:
31
These features involve ground elevations,
variation of mean annual temperature and rainfall
and population densities.
They can be represented by GIS in raster data
structures. Ex. DEM of parts of Wollega
 Generally, earth surface features can be represented and entered in to GIS
database in 3 basic graphical elements: points, lines/polylines and polygons.

32. B) None Spatial Data
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 Refers to the attribute component of GIS data that can
connect the tabular data to a map features .
 It is a statistical information about the spatial data.
 Both continuous and thematic layers contain statistical
information .
Thematic layers contain
o Histogram of data values
o A list of class names
o A list of class values
 These statistics are called attributes.

33.  Attributes are text and numerical data that
are associated with the classes of a thematic
layer or features in a vector layer.
 Attribute information can take the form of
character strings, integer numbers or floating
point numbers.
For raster layers attribute information are stored in the
image files
For vector layers information is stored in either an INFO
file, dbf file, or SDE database
33

34. GIS Data models
1. Raster Data Models
• The simplest data structures
• A cellular organization of spatial data.
• Made up of grid cells/pixels that are organized and
referenced by their row & column position in the
database file.
• Attempt to divide up and represent the landscape
through the use of regular shapes (square).
• Includes satellite imagery, DEM, Digital orthographs and
digital raster graphs.
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35. Satellite Imagery:
• An image is a digital picture of an object.
• Image data consist only of numbers.
• Each number in an image file is a data file value that
sometimes referred as pixels.
• The term pixel is abbreviated from picture element.
• A pixel is the smallest part of a picture (the area being
scanned) with a single value.
• The data file value is the measured brightness value of
the pixel at a specific wavelength.
35

36. Rows
Landsat Image
Raster Data Structure
Columns
Raster/grid Cell/Pixel 36

37. DEM (Digital Elevation Model):
• A database that contains information about the
topography of a landscape.
• Involves grid cells that contains information about
the topography/elevation/ of the landscape.
• Help to extract aspect, ground slope and shaded
relief maps and also help in terrain analysis.
37

38. 2. vector Data Models
 Vector is a quantity with a starting and ending
coordinates and an associated displacement and direction.
 Helps to specify precisely the position of points , lines
and polygons;
o Points: the fundamental primitives
defines the essence of all the
three forms.
o Lines: Sets of connected points.
o Polygons: collections of lines that forms a closed loop.
• Almost any landscape feature on the earth be described
by one of these three shapes or a combination of them.
• The position of each object is defined by the placement in
a map space that is organized by the coordinate system.
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39. Three types of vector model:
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I. Spaghetti Data Model : is a vector data that has not
structured. Ex. Vector data obtained by digitization
II. Topological Data Model: Built on the concept of
topology.
 Topology deals with the spatial r/s b/n connecting or
adjacent features (arcs, nodes, polygons and points).
Ex. The topology of an arc includes from- and to- nodes.

40. • Topology can be defined as the aspects of adjacency,
connectivity and containment.
o Adjacency: describes a landscape feature’s neighbors.
 Can describe the relation of polygons that share
boundary
o Connectivity: Used to describe linear networks.
Ex. A stream system.
o Containment: Allows to describe the landscape
features located with in , or intersect the boundary of
others.
40

41. • Topology eliminates redundant data (coordinates);
b/c an arc may represent a line feature, part of
the boundary of an area feature or both.
41
Arcs

42. III. TIN (Triangulated irregular Networks):
• A vector based model that represents a continuous
surface as a set of contiguous, non-overlapping triangles
(3 vertices).
• For each of the three vertices the X, Y coordinates and
the Z values are encoded
• The triangles are made up of a set of points called
mass points.
42
A
B
C
E
D
6
5
4
3
2
1

43. A comparison of Raster and Vector Data Models
43
Character Raster Vector
Structure
Complexity
Simple Complex
Location Specificity Limited Not Limited
Computational
Efficiency
High Low
Data Volume High Low
Spatial resolution Limited Unlimited
Representation of
Topology
Difficult Not Difficult

44. 44
UNIT: 3
Coordinate System (spatial data referencing)
Question
Why do we need a reference system?
Know where we are
Where to go to get to some point
Direction to travel to get to a point
Communicate to other people how to find places
o Locally
o Globally

45. 45
• A coordinate system is a reference system used to represent the
locations of geographic features within a common geographic
framework.
• Coordinate systems provide a framework for defining real-world
locations.
• the coordinate system is used as the method to automatically
integrate the geographic locations from different datasets into a
common coordinate framework for display and analysis.
Coordinate systems for Spatial data Referencing

46. 46
There are two common types of coordinate systems used in GIS:
A) A global or spherical coordinate system /geographic coordinate
systems/Geographic (3D)
 the primary coordinate system is the geographic (or geodetic,
spherical or spheroidal).
 the geographic coordinates (or latitudes and longitudes) are angular
measures defining the absolute position of a point on the surface of
the globe.
Geographical, or spherical, coordinates are based on the network of
latitude and longitude (Lat/Lon) lines that make up the graticule of
the Earth.

47. 47
• uses a three-dimensional spherical surface to define locations on the
earth.
• A point is referenced by its longitude and latitude values.
 Longitude and latitude are angles measured from the earth's center
to a point on the earth's surface.
 The angles often are measured in degrees.
• Within the graticule, lines of longitude are called meridians, which run
north/south, with the prime meridian at 0° (Greenwich, England).
o Meridians are designated as 0° to 180°, east or west of the
prime meridian.

48. 48

49. • Lines of latitude are called parallels, which run east/west.
• Parallels are designated as 0° at the equator to 90° at the poles.
• The equator is the largest parallel.
• Latitude and longitude are defined with respect to an origin located at
the intersection of the equator and the prime meridian.
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50. Latitudes and Longitudes for a point
50
550N 600E
The geographic coordinates
(or latitudes and
longitudes) are angular
measures defining the
absolute position of a point
on the surface of the
globe.

51. • Lat/Lon coordinates are reported in degrees, minutes, and
seconds
51
Equator
Prime meridian
N
S
South Pole
W
North Pole
E

52. 52
B) A projected coordinate system /map projections
map projections are mathematical formulas that are used to translate
latitude and longitude on the surface of the earth to x and y coordinates
on a plane.
• A projected coordinate system is defined on a flat, two-dimensional
surface.
• It has constant lengths, angles, and areas across the two dimensions.
• It is always based on a geographic coordinate system that is based on
a sphere or spheroid.
• In a projected coordinate system, locations are identified by x,y
coordinates on a grid, with the origin at the center of the grid.

53. • Each position has two values that reference it to that central location.
• One specifies its horizontal position and the other its vertical position.
• The two values are called the x-coordinate & y-coordinate.
• Using this notation, the coordinates at the origin are x = 0 and y = 0.
EX: UTM Coordinate System
 A projection that divide the Earth into 6 degree longitudinal zones
with a central meridian in the center of the zone.
 Extends from 800S & 840N latitudes.
 The coordinates are in meters; making it easy to make accurate
calculations of short distances between points
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54. 54

55. • Projections
55
The earth is a spheroid
The best model of the earth is a globe
not easy to carry
not good for planimetric measurement
Maps are flat
easy to carry
good for measurement
Map projections are created to “project” data from a sphere
onto a planar surface
Projection and transformation

56. Earth to Globe to Map
56

57.  This transformation necessarily distorts some aspect of
the earth's surface, either the area, shape, distance, or
direction.
 All map projections distort the surface in some fashion.
 Depending on the purpose of the map, some distortions
are acceptable and others are not.
57

58. Cartographic (map) projections try to flatten the curved surface of
the globe without stretching or tearing it.
However, since all map projections attempt to represent the curved
surface of the Earth on a flat sheet of paper distortions are inevitable.
The degree of distortion differs from point to point on the sphere and
from map to map.
One easy way to understand how map projections alter spatial
properties is to visualize shining a light through the earth onto a
surface, called the projection surface.
Imagine the earth's surface is clear with the graticule drawn on it.
Wrap a piece of paper around the earth.
A light at the center of the earth will cast the shadows of the
graticule onto the piece of paper. next
58

59. You can now unwrap the paper and lay it flat. The
shape of the graticule on the flat paper is different
from that on the earth.
The map projection has distorted the graticule.
A spheroid can't be flattened to a plane any more
easily than a piece of orange peel can be flattened—
it will rip.
Representing the earth's surface in two dimensions
causes distortion in the shape, area, distance, or
direction of the data.
A map projection uses mathematical formulas to
maintaining spatial relationships on the globe to flat,
planar coordinates.
59

60. • Projections
60
an imaginary light is “projected”
on a “developable surface”
_

61. Three primary flat surfaces are used to describe map
projections: planes, cylinders and cones.
Types of Projections Based on Developable Surfaces
61

62. 62
Three types of projections can be developed from these
surfaces:
1. The cylindrical Projection:
Transferring of meridians, parallels and other points by
wrapping a flat plane/sheet into a cylinder and making it
tangent along a line or lines on the globe. Or a cylinder
circumscribes a globe. The cylinder touches the globe at
the equator.
tangent cylinders

63.  Such projections stretch distances east-west and the
amount of stretch is the same at any chosen latitude on
all cylindrical projections
when unfolding the cylinder:
Meridians are mapped to equally spaced
vertical lines and
 circles of latitude (parallels) are
mapped to horizontal lines
Meridians
Latitudes
63

64. 2. Conical Projection
64
Transferring of parallels and meridians from the
generating globe grid to a cone enveloped around the globe.
The meridians converge at the poles and parallels seem
arcs of circles.
Latitudes
Meridians

65. 3. Azimuthal Projection:
65
• Transferring parallels, meridians and points from the
generating globe to a plane sheet of paper at a point.
• Meridians radiate from the center and paralles become
concentric circles.
Latitudes
Meridians

66. Datum
66
o While a spheroid approximates the shape of the earth, a
datum defines the position of the spheroid relative to the
center of the earth.
o A datum provides a frame of reference for measuring
locations on the surface of the earth.
o It defines the origin and orientation of latitude and
longitude lines.
o It is a smooth, mathematical representation of the earth’s
surface that creates a control surface on w/c an ellipsoid
and other location data are referenced.
o A mathematical surface that fits closely to the mean sea
level surface throughout the area of interest. The surface
to which the ground control measurements are referred.
o Created from large numbers of measurements of the earths
surface.

67. commonly used coordinate systems in GIS
67

68. Geo-referecing
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 There are various definitions for the term ‘georeferencing’.
For example, Sommer and Wade define georeferencing as
‘aligning geographic data to a known coordinate system so it
can be viewed, queried, and analysed with other geographic
data’.
 Coarser views include the domain of georeferencing
multimedia and the exploration of means for the
identification of geographical objects in general.

69. 4. Data entry and preparation
69

70. 4.1 spatial-DATA Sources:
 The most important and expensive component of the Geographic
Information System is Data which is generally known as fuel for GIS.
GIS data is combination of graphic/spatial and tabular data.
 A wide variety of data sources exist for both spatial and attribute data.
The most common general sources for spatial data are:
aerial photographs;
remotely-sensed imagery;
point data, samples from surveys; and
existing digital data files.
70

71. 4.2 Data Entry
The data input process is the operation of encoding both types
of data (geographic and attribute data) into the GIS database
formats.
The most common data input ways are: Data transfer from
instruments, Keyboard Entry, Map Scanning and digitization
A) Data Transfer From Instruments:
 GPS with the total station is one of the instruments from
w/c GIS data can be transferred.
 A GPS device calculates its location using signals received
from the satellites.
 GPS positioning is based on trilateration a method of
determining position by measuring distances to points at
known coordinates.
 At a minimum, trilateration requires 3 ranges to 3 known
points. 71

72. 72
B) Keyboard Entry: Used to enter attribute data as field
observations
C) Map Scanning:
oInvolves the use of scanners for map data conversion.
oThe scanning is used to:
 Obtain digital image data as a base map for other vector
information
 Scanning Requires:
 Captured image is a raster.
 Scanned image needs to be converted to a vector
 Vectorization process that attempts to distill points, lines
and areas from scanned image consisting of pixels removal
of all pixels that make the line wider than one pixel

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C) Digitization:
o Captures map data by tracing lines from a map
o Uses a cursor and an electronically-sensitive tablet
o Result is a string of points with (x, y) values
 Manual digitizing (human operator, control points)
 on-tablet: paper map on tablet
 on-screen: scanned image of map shown on screen
o point mode: mouse location recorded only if
operator says so
o stream mode: near continuous recording of
locations
 Automatic digitizing:
 GIS finds features from scanned image with little
or no interaction from operator
 source document must be scanned first

74. 74
Digitizing process

75. A digitizer is made up of 3 components:
•A table
•A cursor and
•A controller
Cursor
Table
Controller
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76. 76
On-screen versus on-tablet digitising
 On-screen versus on-tablet digitizing
 On-screen more comfortable for the operator
 On-screen generally more accurate ( zooming facilities )
 On-screen faster (semi-automatic, digitising and editing at
the same time)
 On-screen up-dating procedure ( geometrically corrected
satellite imagery and scanned aerial photo’s can be overlaid
with the old vector data )
 Digitizing tablet –easier to do larger maps
 Digitizing tablet –better for worn out maps

77. Digitizing involves:
a) Hardcopy Digitization
• Hardcopy digitizing requires a person to enter coordinate
information through the use of a digitizing tablet and
digitizing puck
– A digitizing tablet is a surface with a fine electrical wire
grid under the surface.
– A digitizing puck is an electrical device with cross hairs
and multiple buttons to perform data entry operations
– An operator then enters the information using the puck.
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79. 79

80. b) On-Screen Digitization
• On-screen digitizing is a combination of scanning and
manual digitizing.
• The main steps in on-screen digitizing typically include:
– Scanning the map
– Registering the map
– Digitizing the map
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