Geography is the study of Earth’s features and patterns of their variations in spatial location and time. Many questions of agricultural production are geographic in nature as the production depends on the environment and prevailing socio economic conditions, both of which vary spatially and in time

1. GENERAL GIS CONCEPTS
by
CH KALI PRASAD
MAPPING PROFESSIONAL

2. 2
INDEX
• Define GIS
1
• Explain principal application areas of GIS
2
• Differentiate between GIS and other Information systems
3
• Describe Geographical Approach
4
• Describe Functions of GIS
5

3. Planet Earth has Seven Billion people today.
Who else are living with us?
3
PLANET EARTH IN PERSPECTIVE

4. What else are associated with us?
Where are they? How big are they?
How much more Danger can we bear to keep fit and healthy?
4
THE EARTH
AND ITS ENVIRONMENT

5. Do you have an answer how can we monitor, model
these occurrences on the earth with respect to our lives?
Is there any method or system which helps us to record, plan and
model the phenomenon happening around us?
5
The answer is “Geographic Information System .”
THE EARTH
AND ITS ENVIRONMENT

6. GIS stands for [ ] [ ] [ ]
A GIS stores geographic information in a [ ] and displays it on a map.
GIS maps are [ ].
A GIS stores two type of geographic information: features and [ ]
The functions of GIS are [ ], geo-data [ ] and
Geographic[ ].
People use the information from a GIS to make decisions and [ ]
Problems.
6
WHAT IS THE
DEFINITION OF GIS?
analysis
attributes
database
dynamic
geographic
information
management
solve
system
visualization
geographic information system
database
dynamic
attributes
solve
visualization management
analysis
*Source ESRI

7. 7
PRINCIPAL APPLICATIONS AREAS OF GIS
Mapping and charting
Natural resources
Transportation
Utilities and communications
Public safety

8. 8
Education
Government
Defense and Intelligence
Business
Health and Human services
PRINCIPAL APPLICATIONS AREAS OF GIS

9. 9
GIS AND OTHER
INFORMATION SYSTEMS
A major difference between GIS and other information systems
is that GIS can simulate the real world with its capability to
construct and maintain the spatial relationship of real world
features
• In early graphics systems, the data model was simple and
consisted almost entirely of symbolized graphic features
• General-purpose, spatial data management requires a database
structure & software technology beyond the graphic functionality.
• A GIS data model involves storage of tabular data (attributes) in
association with very simple cartographic features (points, lines,
and polygons)

10. 10
GIS data model, while similar to CAD approach in that it uses
coordinates, is fundamentally different in its simplicity & approach
• Common to the GIS is the use of topology (networks) to
store relationships among various spatial objects
• Topology involves the use of graph theory to abstract &
relate cartographic objects using a series of arcs and
nodes
• This represents a different and superior structure for
geographic data management as compared with the “graphics
model”
GIS AND OTHER
INFORMATION SYSTEMS

11. GIS
loss of
biodiversity
climate
change
pollution
over
population
limited
resources
political
conflicts
11
A GEOGRAPHIC APPROACH [1]
There are many problems that challenge our world and its future
To combat these problems we need understanding
knowledge, and integrated approaches

12. By combining the science of geography with the
technology of GIS, we can
• Collect and organize the data for better understanding
of the Earth.
• Analyze data to create geographic knowledge.
• Apply geographic knowledge to find solutions we call
this as “a geographic approach”
12
A GEOGRAPHIC APPROACH [2]

13. Today a wide variety of disciplines and Organizations
use geographic approach to
• Automate workflows
• Organize key information
• Use recourse wisely
• Make and support decisions
13
A GEOGRAPHIC APPROACH [3]

14. 14
A GIS has 3 primary functions
FUNCTIONS OF GIS [1]
Visualization Looking at different views of your
geographic data. Visualization
allows you to gain information and
see relationships.
Geo data management Organizing and updating geographic data
to make it useful.
Analysis Applying GIS tools to geographic data to
answer questions and make decisions.

15. • Suppose you own several book shops and you want to expand
in the same city. Where are potential areas for a new shop?
• First map existing book shop locations, demographic data, city
zoning data
15
FUNCTIONS OF GIS [2]
Existing book shop locations Demographic data City zoning

16. Then use GIS tools to combine the data and find areas
that meet your criteria
16
FUNCTIONS OF GIS [3]
Map showing potential areas for new book stores
Potential areas for
a new book store

17. 17
TOPIC 2: COMPONENTS AND SUB
SYSTEMS OF GIS

18. 18
INDEX
• Describe the Components of GIS
1
• Describe subsystems of GIS
2

19. 19
COMPONENTS OF GIS
A Geographic Information
System is a system of
computer software,
hardware and data, and the
personnel that make it
possible to enter,
manipulate, analyze, and
present information that is
tied to a location on the
earth’s surface.

20. 20
HARDWARE/SOFTWARE
Hardware is the computer on which a GIS
operates.
The software runs on a wide range of
hardware types, from centralized computer
servers to desktop computers used in
stand-alone or networked configurations.
GIS software provides functions and tools
needed to input and store geographic
information.
It also provides query tools, performs
analysis, and displays geographic
information in the form of maps or reports
Hardware
software
http://www.clker.com/clipart-1796.html

21. 21
DATA
Data is one of the most important, and
often most expensive, components of a
GIS.
Geographic data, which is comprised of
geographic features and their
corresponding attribute information, is
entered into a GIS using a technique called
digitizing.
Digitizing is done by tracing the location,
path or boundary of geographic features
either on a computer screen using a
scanned map in the background, or a paper
map that is attached to a digitizing tablet.
a
ema-inc.com
GIS data
Digitization
.
http://proceedings.esri.com/library/userconf/proc01/professional/papers/pap894/p
894.htm

22. 22
PEOPLE AND METHODS
The real power of a GIS comes from the
people who use them.
Today GIS is being used by people, in many
different fields, as a tool that enables them
to perform their jobs more effectively.
GIS users range from technical specialists
who design and maintain the system to
those who use it to help them do their
everyday work.
A successful GIS operates according to a
well-designed plan and business rules,
which are the models and operating
practices unique to each organization.
lagic.lsu.edu

23. Data input
Data
storage and
retrieval
Data
manageme
nt and
Analysis
Data
output and
Display
23
GIS SUBSYSTEMS

24. • Allows the user to capture, collect, and transform
spatial and thematic data into digital form
24
DATA INPUT
Aerial photographs
Remotely sensed images
Scanned maps
Survey documents
Reports

25. • The data storage and retrieval subsystem organizes
spatial and attribute data
25
DATA STORAGE AND
RETRIEVAL
Database Management
System (DBMS)
Spatial data is encoded and
maintained in proprietary file
format

26. Allows the user to define and execute spatial
and attribute procedures to generate derived
information.
 Commonly thought of as the heart of a GIS
 Distinguishes GIS from other database information
systems and Computer Aided Drafting (CAD)
systems.
26
DATA MANIPULATION AND
ANALYSIS

27. GIS output contains the following
• Maps
• Reports
• Charts
27
DATA OUTPUT AND DISPLAY

28. 28
TOPIC 3: AN INTRODUCTION TO GIS DATA
MODELS

29. 29
INDEX
• GIS data models
1
• Explain Vector data model
2
• Explain Raster data model
3
• Differentiate between Vector and Raster Data models
4
• Describe GIS attributes and tables
5

30. All spatial data models are approaches for storing the spatial
location of geographic features in a data base. Three basic
types of spatial data models have evolved for storing
geographic data digitally.
• Vector
• Raster
• TIN
30
DATA MODELS [1]

31. Vector Representation
X-AXIS
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600
500
400
300
200
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Y-AXIS
River
House
600
Trees
Trees
B
B
B B
B
B
B
B G
G
BK
B
B
B
G
G
G G
G
Raster Representation
1 2 3 4 5 6 7 8 9 10
1
2
3
4
5
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7
8
9
10
Real World
G
G
DATA MODELS [2]
31

32. • Vector data model:
Vector data model
represents geographic
objects with the basic
elements points, lines
and areas, also called
polygons.
32
Point
line
Polygon
DATA MODELS [3]

33. A city can be represented as a point
A river can be represented as a line
33
VECTOR DATA MODEL
A country can be represented as
a polygon

34. • Raster datasets represent
geographic features by
dividing the world into
discrete square or
rectangular cells laid out in a
grid. Each cell has a value
that is used to represent
some characteristic of that
location.
• Raster data includes images
and grids.
34
RASTER DATA MODEL[1]

35. • Grids represent derived data and are often used for analysis
and modeling.
• Grids can store continuous values, such as for an elevation
• They can also store categories, such as for a grid of
vegetation types.
35
RASTER DATA MODEL[2]

36. 36
Data can be represented at its
original resolution and form without
generalization.
Due to the nature of the data storage
technique data analysis is usually
easy to program and quick to
perform.
For effective analysis, vector data must be
converted into a topological structure. This
is often processing intensive and usually
requires extensive data cleaning
The inherent nature of raster maps, e.g.
one attribute maps, is ideally suited for
mathematical modeling and quantitative
analysis.
Accurate geographic location of data
is maintained.
Discrete data, e.g. forestry stands, is
accommodated equally well as continuous
data, e.g. elevation data, and facilitates the
integrating of the two data types
Graphic output is usually more aesthetic Most output maps from grid-cell systems
do not conform to high-quality
cartographic needs.
VECTOR vs RASTER DATA MODELS

37. • TIN model is somewhat more complex
than the simple point, line, and polygon
vector model, or the raster model, it is
actually quite useful for representing
elevations.
• A triangulated irregular network (TIN) is a
data model that is used to represent
three dimensional objects. In this case,
x,y, and z values represent points. Using
methods of computational geometry, the
points are connected into what is called a
triangulation, forming a network of
triangles.
37
TIN MODELS
TIN data model

38. • On a GIS map, there's more to a feature than its location and
shape. There's all the information associated with that
feature.
• For a road, this might include its name, speed limit, and
whether it's one-way or two-way.
• For a city, this might include its population, demographic
characteristics, number of schools, and average monthly
temperatures.
38
GIS MAPS-ATTRIBUTES [1]

39. • A particular type, or category, of
information associated with a feature
in a GIS is called an attribute.
• For example, population can be an
attribute of a city, country, continent,
and other features. Feature attributes
are stored in an attribute table.
39
GIS MAPS-ATTRIBUTES [2]

40. • A feature on a GIS map is linked to
its record in the attribute table by a
unique numerical identifier (ID)
• Because features on the map are
linked to their records in the table,
you can click a feature on the map
and see the attributes stored for it in
the table. When you select a record
in the table, the linked feature on
the map is automatically selected as
well
40
GIS MAPS-ATTRIBUTES [3]

41. • A separate data model is used to store and maintain attribute
data for GIS software.
 Tabular
 Hierarchical
 Network
 Relational
 Object Oriented
41
ATTRIBUTE DATA MODEL

42. 42
TOPIC 4: TOPOLOGY

43. 43
INDEX
• Define topology
1
• Explain the topological elements and relationships
2
• Describe common topological data models
3
• Explain topology storage format in GIS
4

44. It is believed that a topologic
data model best reflects the
geography of the real world and
provides an effective
mathematical foundation for
encoding spatial relationships,
providing a data model for
manipulating and analyzing
vector based data.
44
TOPOLOGY
http://webhelp.esri.com/arcgisdesktop/9.3/index.cfm?To
picName=topology%20basics

45. In essence Topology is a mathematical approach that allows us to structure
spatial data based on the principles of feature adjacency and feature
connectivity. It is in fact the mathematical method used to define spatial
relationships.
For example, some common spatial relationships and rules include the following:
• Parcels cannot overlap. Adjacent parcels have shared boundaries
• Stream lines cannot overlap and must connect to one another at their endpoints.
• Road centerlines must connect at their endpoints.
Each of these situations defines a potential case for using topology rules
to maintain data integrity.
45
TOPOLOGY

46. 46
COMMON TOPOLOGICAL
DATA MODELS
Source: http://www.fpa.nifc.gov/

47. 47
TOPOLOGICAL ELEMENTS
Single arcs Connected set of arcs
Polygons bounded by arcs
The most common topological data
structure is the arc/node data model.
This model contains two basic entities,
the arc and the node.
• The arc is a series of points, joined by
straight line segments, that start and end
at a node.
• The node is an intersection point where
two or more arcs meet. Nodes also occur
at the end of a dangling arc.
• A polygon feature is comprised of a
closed chain of arcs.

48. 48
TOPOLOGY STORAGE
In GIS software the topological
definition is commonly stored in
a proprietary format
most software offerings record
the topological definition in
three tables
•The node table stores
information about the node and
the arcs that are connected to it
•The arc table contains
topological information about
the arcs.
•The polygon table defines the
arcs that make up each polygon.
dusk.geo.orst.edu Arc/node map data structure with file – GRAPHIC

49. 49
TOPIC 5: THEMATIC MAPS

50. Transforming Business - Enriching Lives 50
INDEX
• Define Thematic map
1
• Common techniques of depicting data on a thematic map
2
• Explain Types of Thematic maps
3

51. 51
THEMATIC MAPS
Thematic maps are used to communicate geographic
concepts like the distribution of densities, spatial
relationships, magnitudes, movements etc.
World climate or soils maps are notable examples of
thematic maps.
There are five common techniques for depicting
geography data on a thematic map.
The most common is a choropleth map that uses color
to show variations in quantity, density, percent, etc.
within a defined geographic area. Each color usually
depicts a range of values. Soil map of India

52. 52
There are many different types of thematic maps.
Each uses a different symbol to depict information.
Four of the most common types are given below
TYPES OF THEMATIC MAPS
• Choropleth map
• Dot maps
• Graduated circle maps
• Isoline maps

53. 53
TOPIC 6: DATA QUALITY

54. Transforming Business - Enriching Lives 54
INDEX
• Describe Data quality in GIS
1
• Explain completeness
2
• Explain Logical consistency
3
• Explain Positional accuracy
4

55. 55
DATA QUALITY
The Implications of using low-quality data in important
decisions is potentially severe.
There are certain terms which defines the quality of GIS data
• Completeness
• Logical consistency
• Positional accuracy

56. 56
COMPLETENESS
Completeness refers to whether there are data lacking in the
data base to what exists in the real-world
It is important to be able to assess what does and what does not
belong to a complete data set as intended by it’s producer.
It might be incomplete or over complete within the scope of the
data set as it is defined.
Completeness can relate to either spatial, temporal or thematic
aspects of data set.

57. 57
LOGICAL CONSISTENCY
For any particular application predefines logical rules
concerns ,these include:
•The compatibility of data with other data in a data set
•The absence of any contradictions within a data set
•The topological consistency of the data set
•The allowed attribute value ranges as well as combinations
of attributes

58. 58
POSITIONAL ACCURACY
All measurements made with surveying and photogrammetric
instruments are subject to error These include:
Human errors for measurements generally referred to as gross errors or
blunders. these are usually large errors resulting from carelessness
which would be avoided through careful observation
Instrumental or systematic errors
This leads to errors that vary systematically in sign or magnitude
.systematic errors are particularly dangerous because they tend to
accumulate.
Random errors caused by natural variations in the quantity being
measured. these are effectively the errors that remain after blunders
and systematic errors have been removed.

59. 59
TOPIC 7: META DATA, DEVICES AND FILE
TYPES

60. 60
METADATA
Metadata is defined as background information that describes
all necessary information about the data it self. more generally it
is known as “data about data”
This includes
Identification information : Data sources, time of acquisition ,
etc.
Data quality information : Positional, attribute and temporal
accuracy, lineage
Entity and attribute information: Related attributes, unit of
measure ,etc.

61. 61
Meta data answer who what ,when, where ,why and how
questions about all facets of the data
Maintaining meta data is an key part in maintaining data and
information quality in GIS.
This can serve different purpose from description of data it
self through providing instruction for data handling.
METADATA

62. Digitizers:
A digitizer is the device used for digitizing
features from a hard copy map,
Scanners:
scanners sometimes can replace digitizing by
automatically converting hard-copy maps to
a digital raster file
printer/plotter:
These devices are used to produce a
hardcopy map
optical disks, magnetic disks
used to store the information
62
DEVICES AND FILE TYPES

63. • The format of the file describes in which way the geographical features
have been saved. It is very important to consider the file format of GIS
data because software programs rarely support all file types
• If you want to use GIS data that was saved in a particular format not
supported by your GIS program, you must either find a way to
transform the data or simply use another GIS program.
• most GIS programs support other formats by having functions to
import and export datasets.
• Below is a list of some of the most common GIS file formats
63
DEVICES AND FILE TYPES

64. 64
VECTOR FILE FORMATS
File format Name Description
ARC ESRI Generate Line Simple ASCII format which can handle point and line
data.
DGN MicroStation Design Files DGN is an intern format for MicroStation, a CAD
program
DLG Digital Line Graphs DLG is used by the US Geological Survey (USGS) for
handling vector information from printed paper maps
DWG Autodesk Drawing Files DWG is an intern format for AutoCAD. AutoCAD can
convert DWG files to DXF files without loosing graphic
information
E00 ARC/INFO interchange file E00 is a transfer format available both as ASCII and
binary form.
SHP ESRI shapefile Shape is Arc View's internal format for vector data.
WMF Microsoft Windows Metafile WMF is a vector file format for Microsoft Windows
Operation Systems

65. • Raster files are used generally to save images, like for
example, a scanned paper map, digital photographs or
satellite images, but also to save variables which continuously
vary in space, like topography and temperature.
• Images from satellites, or other aircrafts, are known as
remote sensing data. The resolution of the remote sensing
data and scanned maps refers to the area on the ground
covered by one pixel.
• This differs to other image data, where the resolution is given
in dots per inch (dpi).
65
RASTER FILE FORMATS

66. File
format
Name Description
ADRG Arc Digitized Raster Graphics ADRG is a format created by the US military to save paper
maps in raster format
BIL Band Interleaved by Line BIL is a computer compatible tape (CCT) format that
stores all bands of remotely sensed data in one image file.
BIP Band Interleaved by Pixel the BIP image format, each line of an image is stored
sequentially
BSQ Band Sequential BSQ is a computer compatible t ape (CCT) format that
stores each band of satellite data in one image file for all
scan lines in the imagery array
DEM Digital Elevation Model DEM is a raster format created by the USGS (US Geological
Survey) for saving elevation data
GeoTIFF GeoTIFF GeoTIFF is a form of TIFF (Tag Image File Format) format
for geo-referenced raster data
TIFF Tagged Image File Format Like PCX, TIFF is a common raster format produced by
drawing programs and scanners
66
RASTER FILE FORMATS

67. 67
GEOGRAPHIC INFORMATION
SYSTEM MATTERS
Today’s challenges to safe guard these
Seven Billion People….
require geographic approach to Model our
Earth for…
• Climate Change
• Urban Growth
• Sustainable Agriculture
• Water Quality and Availability
• International & National Security
Energy
• Epidemiology/Disease Tracking
• Natural Hazards: Seismicity, Weather Events
http://yohipster.com/wp-content/uploads/2011/10/7_billion.png
engineeringchallenges.org