Introduction and Application of GIS

Introduction and Application
of GIS
Prepared by
Prof. S. G. Taji
Dept. of Civil Engineering
S.R.E.S’s College of Engineering, Kopargaon
Content Beyond Syllabus
18/09/2017

Geographic Information Systems (GIS)
 There are a number of definitions of GIS
 GIS is much more than a container of maps in
digital form”.
 A GIS is a system (hardware + database engine)
that is designed to efficiently, assemble, store,
update, analyze, manipulate, and display
geographically referenced information (data
identified by their locations).

 GEOGRAPHIC
 implies that locations of the data items are known, or can
be calculated, in terms of Geographic coordinates
(Latitude, Longitude)
 INFORMATION
 implies that the data in a GIS are organized to yield useful
knowledge, often as colored maps and images, but also as
statistical graphics, tables, and various on-screen
responses to interactive queries.
 SYSTEM
 implies that a GIS is made up from several inter-related
and linked components with different functions. Thus, GIS
have functional capabilities for data capture, input,
manipulation, transformation, visualization,
combinations, query, analysis, modeling and output.

 Hardware
 Computer
 Digitizer and Scanner
 Printer/Plotter
 Software
 GIS software provides the functions and tools needed to store,
analyze, and display geographic information.
 Tools for entering and manipulating geographic
information such as addresses or political boundaries
 A database management system (DBMS)
 Tools that create intelligent digital maps you can analyze,
query for more information, or print for presentation
 An easy-to-use graphical user interface (GUI)

 GIS software, allows you to interactively work with
spatial data
 There are a number of Geographical Information
Systems (GIS) (or GIS software) available today:
 Web-based GIS
 Geobrowser: Google Earth
 Desktop GIS: ArcGIS
 QGIS

 Web-based GIS
 Web-based GIS, or WebGIS, are online GIS applications
which in most cases are excellent data visualisation
tools
 Geobrowser: Google Earth
 Geobrowser can be understood as an Internet Explorer
for geographic information
 The biggest difference between the World Wide Web
and the geographic web however is that everything
within the latter is spatially referenced.
 Google Earth is the most popular geobrowser available

 Desktop GIS: ArcGIS
 A desktop GIS is a mapping software that needs to be
installed onto and runs on a personal computer.
 we will use ArcGIS, which is developed by ESRI
 ArcGIS is what ESRI refer to as a suite of products
which can be tailored to your need. ArcGIS is used for a
vast range of activities, covering both commercial and
educational uses.

QGIS
 Quantum GIS developed in 2002 and undergone
significant development.
 It is open source software which is freely available
 QGIS runs on Windows, various Linux distributions,
Unix, Mac OS X, and Android.
 Features of QGIS include;
 Importing data from multiple sources
 Digitizing
 Editing
 Geoprocessing
 Raster processing

 Data:-
 GIS incorporates geographical features with tabular data in
order to map, analyze, and assess real-world problems.
 Data that is in some way referenced to locations on the
earth. Attribute data can be generally defined as additional
information about each of the spatial features.
 Geographic data and related tabular data can be produced
by digitizing images from aerial photographs or published
maps.
 An example of this would be college. The actual location of
the College is the spatial data.
 Additional data such as the College name, specialization,
capacity would make up the attribute data.

 People
 GIS users range from technical specialists who design
and maintain the system to those who use it to help
them perform their everyday work.
 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

Co-ordinate systems
 Geographic Coordinates - such as latitude and
longitude
 These are usually referred by degrees, minutes, and seconds,
e.g. 56°27'40" and 116°11'25".
 Map Projection - Coordinates are measured in
metres,
 e.g. Universe Transverse Mercator (UTM) e.g. 545,000.000
and 6,453,254.000
 normally reference to a central meridian. Eastings refer to X
coordinates while Northings refer to Y coordinates.

GEOGRAPHIC COORDINATE SYSTEMS
 The geocentric coordinate system is not a map
projection.
 The earth is modelled as a sphere or spheroid
in a right handed X,Y,Z system.
 The X-axis points to the prime meridian, the
Y-axis points 90 degrees away in the equatorial
plane, and the Z-axis
points in the direction
of the North Pole.

 Equator is imaginary line which split Earth
Horizontally in two parts
i.e. It separates North and South pole from the
centre.
 Meridian is imaginary line which split Earth
vertically in two parts (it runs through Greenwich,
England).
i.e. It separates Western and South
Hemisphere.

 Latitude and longitude are imaginary (unreal)
lines drawn on maps to easily locate places on
the Earth.
 Latitude is distance north or south of the
equator
 Longitude is distance east or west of the prime
meridian
 Both are measured from the center of earth in
terms of the 360 degrees (symbolized by °) of a
circle.
 In the spherical system, horizontal lines, or east–
west lines, are lines of equal latitude, or parallels.
 Vertical lines, or north–south lines, are lines of
equal longitude, or meridians.

Introduction and Application of GIS

CHARACTERIZING GEOGRAPHIC FEATURES
 All geographic features on the earth's surface can be
characterized as one of three basic feature types:
 Point data exists when a feature is associated with a
single location in space.
 Ex. well, a weather station, etc.
 Linear data exists when a feature's location is
described by a string of spatial coordinates.
 Ex. rivers, roads, pipelines, etc.
 Areal data exists when a feature is described by a
closed string of spatial coordinates
 Commonly referred to as a polygon.
 Ex. forest stands, soil classification areas, administrative
boundaries, and climate zones, etc.

GIS DATA TYPES
 Accordingly, GIS technology utilizes two basic types
of data
1. Spatial Data - Describes the absolute and relative
location of geographic features.
2. Attribute data - Describes characteristics of the
spatial features
 The coordinate location of a watershed would
be spatial data, while the characteristics of that
watershed, e.g. catchment area , type of soil,
elevations, etc., would be attribute data.

Spatial Data
 Traditionally spatial data has been stored and
presented in the form of a map.
 Three basic types of spatial data models have
evolved for storing geographic data digitally.
These are referred to as:
1. Raster
2. Vector

1) Raster
• Data is classified as “continuous” (such as in an
image), or “thematic” (where each cell denotes a
feature type.
• Stores images as rows and columns of numbers
with a Digital Value/Number (DN) for each cell
• Units are usually represented as square grid cells
that are uniform in size
• Numerous data formats
(TIFF, GIF, ERDAS img,
CAD Drawings, etc)

2) Vector
 Allows user to specify specific spatial locations
 It not broken up into discrete grid squares
 information about points, lines, and polygons is encoded
and stored as a collection of x & y coordinates.
 Numerous data formats- SHP, KML, GNT, etc.
point
1,6
2,5
5,4
4,1
7,10
5,9
4,7
6,6
8,6
9,8
li ne
polygon
2,2
5 10
5
10
as geometric objects:
points, lines, polygons

Importance of Layers in GIS
• Geographic data =
Representation of reality
• Reality is complex.
• GIS utilizes a layer approach
• Each layer only includes
information about one type of
phenomenon.
• Data layers must be aligned
with one another

Modeling Geospatial Reality
Real World
Vector Model
Raster Model

Coding Vector GIS
Reality Vector Mode Model of Reality

Coding Vector GIS
Polygon
I
Polygon
node
II
Polygon
III
Polygon
V
Polygon
IV
node
A
node
B
node
C
E
node
F
node
G
node
D
Reality Vector Mode Model of Reality

Coding Raster GIS Data
Reality Raster Mode Model of Reality

Coding Raster GIS Data
Reality Raster Mode Model of Reality
1 1 1 1 2 3 4 4
1 1 1 2 2 3 4 4
1 2 2 2 3 3 4 4
2 2 2 3 3 4 4 4
3 3 3 3 5 5 5 5
1 1 1 1 6 5 5 5
1 1 1 1 1 5 5 5
1 1 1 1 1 1 5 5

Remote Sensing
• Remotely-Sensed data is one of the most important
sources of data for GIS.
• RS means - Acquiring data from a distance
• Usually uses electromagnetic energy
– sunlight, radar, laser
• Originally captured on photographic film
• Recent platforms utilize digital sensors

Early Remote Sensing Platforms

What kinds of devices collect the data?
• Aircraft
– High altitude
– Low altitude
Geosynchronous Orbit
• Spacecraft:
– Landsat
– SPOT
– Weather satellites
– GeoEye-1
when the satellite moves at
the same speed as the
spinning earth – results in the
camera staying over the same
spot of the earth

Application of GIS in Hydrology
I. Surface Water Hydrology
 Data Required :
 Terrain
 Digital elevation models
 Slope and aspect
 Watersheds and sub-catchments
 Drainage network
 Soil
• Permeability
• Layer depth
• Soil textural and Soil water content
•Precipitation & climate
•Rain-gauge data
•Gauge locations &
context
•Statistics(e.g.,
intensity, duration)
•Temperature
•Evaporation &
transpiration

 Analysis of Data & Final Output :
 Watershed Management
 Terrain modeling
 Flow modeling
 Debris flow probability
 Flood Management
 Flood plain delineation
 Channel characteristics
 Inundation modeling
 Infrastructure analysis
 Risk modeling and mitigation

II. Groundwater Modeling
 Data Required :
 Weather
 Topography
 Land cover type
 Water levels and geologic data from no. of groundwater
wells
 Analysis & Output
 Ground water model
 Groundwater development and
 Artificial recharge sites

Example
 Project Planning for a Storage Structure
 In this example, a dam is proposed to be constructed
across a river, for which the following information may
be required:
i. Watershed area contributing to the project site
ii. Reservoir surface area and volume, given the
height of the dam
iii. Villages that may be inundated under reservoir

 For the above, the following themes may be stored in
a GIS:
 Elevation contours of the watershed area, including
the project site
o For this, DEM is required
 Satellite image derived land-use map of the
watershed
o For this, Satellite images which shows land use/land
cover data is required
 Village boundary map, showing location of
habitation clusters
o For this, digital map which shows village boundaries
and other important structure is required

 Using the above data, one may obtain desired in
information as follows:
i. Watershed area may be found by using the
elevation contour data, and using a suitable GIS
software that has a tool to delineate the
watershed boundary.
ii. Once the boundary is identified, the area
calculation tool may be used in the GIS software
to calculate the watershed area.
iii. Reservoir surface area can similarly found using
the area calculation tool.

iv. Volume calculation tool of the GIS software may be
used to find out the storage volume, which is the
space between a plane at the reservoir surface and
the reservoir bottom.
v. By overlying the reservoir extent over the village
boundary map and the locations of habitation
clusters one may identify the villages that are likely
to be inundated once the reservoir comes up.
vi. The area of the cultivable village farms that would be
submerged may also be similarly identified, as it
would be required to pay compensation for the loss
to the villagers.

Introduction and Application of GIS

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