1. Geospatial Analysis of Remote
Sensing Data using different Image
Processing Softwares and
Programming in MATLAB
Ranu Bhardwaj
Ph.D. Scholar
(Amity University)
2. Syllabus
Basic concept of Remote Sensing
Geographic Information System (GIS)
Photogrammetry
Spatial Analysis
Image Processing techniques
2
3. Day 1
Geospatial data
Geospatial Technology
Natural Remote Sensing
Remote Sensing in daily life
Definition of Remote Sensing
Concept of Remote Sensing
History of Remote Sensing
Modern day Remote Sensing using satellites
Early Pictures of satellites
Evolvement of Remote sensing
3
5. What is
Geo-spatial
data
The word geospatial is used to indicate that data that has a geographic
component to it. This means that the records in a dataset have
locational information tied to them such as geographic data in the form
of coordinates, address, city, or ZIP code. GIS data is a form of geospatial
data. Other geospatial data can originate from GPS data, satellite
imagery, and geotagging.
5
7. What is Geospatial
Technology
Geospatial technology refers to all of the
technology used to acquire, manipulate, and
store geographic information.
GIS is one form of geospatial
technology. GPS, remote sensing are other
examples of geospatial technology.
7
14. (A) Energy Source or Illumination – Emits Electromagnetic radiation towards earth surface.
(B) Radiation and the Atmosphere – As energy source emits its radiation, it passes through the atmosphere and comes towards
the earth. There are many atmospheric particles in the atmosphere, due to which some of the energy reflected, some of the energy
scattered in the atmosphere and rest energy strikes on the earth features.
(C) Interaction with the Target - once the energy makes its way to the target through the atmosphere, it interacts with the target
depending on the properties of both the target and the radiation.
(D) Recording of Energy by the Sensor- after the energy has been scattered by, or emitted from the target, we require a sensor
(remote - not in contact with the target) to collect and record the electromagnetic radiation.
(E) Transmission, Reception, and Processing- the energy recorded by the sensor has to be transmitted, often in electronic form, to
a receiving and processing station where the data are processed into an image (hardcopy and/or digital).
(F) Interpretation and Analysis- the processed image is interpreted, visually and/or digitally or electronically, to extract information
about the target which was illuminated.
(G) Application
Concept of Remote Sensing
14
15. Definitionsof
RemoteSensing
Theterm“remote sensing”initsbroadest sensemerely means “reconnaissanceat
a distance.”(Colwell,1966, p. 71)
Remotesensinghasbeenvariouslydefined but basically it istheart or science of
telling something about an object without touching it. (Fischer et al., 1976, p.
34)
Remote sensing is the acquisition of physical data of an object without touch or
contact.(Lintzand Simonett,1976, p. 1)
Remote sensing is the observation of a target by a device separated from it by
somedistance.(Barrett and Curtis,1976, p. 3)
Remote sensing is the art, science and technology of obtaining reliable
information about physical objects and the environment, through the process of
recording, measuring and interpreting imagery and digital representations of
energy patterns derived from noncontact sensor systems (Lecture Note by
Wataru, 2009)
15
16. Historyof
Remote Sensing
Natural:
Oldest Compound Eyes
Artificial:
1800: Discoveryof Infrared by SirWilliam Herschel
1826: JosephNiepce tookthefirst photograph
1839: Beginningof practice of photography
1858: Gaspard Tournachontakesfirst aerial photographfrom a balloon
1847: Infrared spectrumshownbyA.H.L.Fizeauand J.B.L.Foucaultto share properties with visible
light
1873: Theoryof electromagnetic energy developed by JamesClerk Maxwell
1909: Photographyfrom airplanes
1914-1918 World War I:Aerial reconnaissance
1920–1930: Developmentand initial applications of aerial photography and photogrammetry
16
17. 1929–1939: Economicdepressiongeneratesenvironmentalcrisesthat lead to
governmentalapplicationsof aerial photography
1930–1940: Developmentof radarsinGermany,US,and UK
1939–1945: World War II:applicationsof nonvisibleportionsof electromagnetic
spectrum;trainingof personsinacquisitionandinterpretationof airphotos
1950–1960: Military researchand development
1956: Colwell’sresearchonplant diseasedetectionwithinfrared photography
1960–1970: Firstuseof termremotesensingTIROSweathersatellite Skylab remote sensing
observationsfromspace
1972: Launchof Landsat1
1970–1980: Rapidadvancesindigital image processing
1980–1990: Landsat4: newgenerationof Landsatsensors
1986: SPOTFrenchEarthobservationsatellite
1980s: Developmentof hyperspectral sensors
1990s: Global remotesensingsystems,lidars
Historyof
Remote Sensing
17
19. HistoryofRemote Sensing
11
First Aerial Photograph from Airplane:
Italy 24-04-1909 (Oblique view of walls
of Centocelli Italy, by Wibur Wright)
The first photo taken
from balloon (1858) 19
20. Historyof Remote Sensing
12
Early aerial photography by the U.S. Navy, 1914. This photograph illustrates
difficulties encountered in early efforts to match the camera with the airplane
20
26. Whatdowesensein
Remote Sensing
By recording emitted or reflected radiation and
applying knowledge of its behaviour as it passes
through the Earth’s atmosphere and interacts with
objects, remote sensing analysts develop knowledge
of the character of features such as vegetation,
structures, soils, rock, or water bodies on the
Earth’s surface.
17
26
27. Electromagnetic(EM) Spectrum
18
The most familiar form of EMR is visible light, which forms only a small (but very important) portion of the full EM spectrum.
The large segments of this spectrum that lie outside the visible range require our special attention because they may behave in
ways that are quite foreign to our everyday experience with visible radiation.
Entertainment/communication Use it as Invisible to human eye Visible range can damage Produce by Useful for
heat source but its heat can be feel tissue accelerating killing cancer
Electrons cells
Entertainment/communication Use it as Invisible to human eye Visible range can damage Produce by Useful for
heat source but its heat can be feel tissue accelerating killing cancer
Electrons cells
27
29. Various Stepsin RS
23
(A) Energy Source
(B) Radiation and the Atmosphere
(C) Interaction with the Target
(D) Recording of Energy by the
Sensor
(E) Transmission, Reception, and
Processing
(F) Interpretation and Analysis
(G) Application
29
38. Radiometric Resolution
Imagery data are represented by
positive digital numbers which
vary from 0 to (one less than) a
selected power of 2.
This range corresponds to the
number of bits used for coding
numbers in binary format. Each bit
records an exponent of power 2
(e.g. 1 bit=2 1=2).
The maximum number of
brightness levels available depends
on the number of bits used in
representing the energy recorded.
Thus, if a sensor used 8 bits to
record the data, there would be
28=256 digital values available,
ranging from 0 to 255.
38
39. Elements of Image Interpretation
Shape:
• Many natural and human-made features have unique
shapes.
• Often used are adjectives like linear, curvilinear, circular,
elliptical, radial, square, rectangular, triangular,
hexagonal, star, elongated, and amorphous.
39
41. Shadow:
Shadow reduction is of concern in remote sensing because shadows
tend to obscure objects that might otherwise be detected.
However, the shadow cast by an object may be
the only real clue to its identity.
Shadows can also provide information on the height of an
object either qualitatively or quantitatively.
41
43. Elements of Image Interpretation
Tone and Color:
A band of EMR recorded by a remote sensing instrument can be
displayed on an image in shades of gray ranging from black to white.
These shades are called “tones”, and can be qualitatively referred to as
dark, light, or intermediate (humans can see 40-50 tones).
Tone is related to the amount of light reflected from the scene in a specific
wavelength interval (band).
43
45. Elements of Image Interpretation
Texture:
Texture refers to the arrangement of tone or color
in an image.
Useful because Earth features that exhibit similar
tones often exhibit different textures.
Adjectives include smooth (uniform, homogeneous), intermediate, and
rough (coarse, heterogeneous).
45
47. Elements of Image Interpretation
Pattern:
Pattern is the spatial arrangement of objects on
the landscape.
General descriptions include random and systematic; natural
and human-made.
More specific descriptions include circular, oval,
curvilinear, linear, radiating, rectangular, etc.
47
49. Elements of Image Interpretation
Height and Depth:
As discussed, shadows can often offer clues to the
height of objects.
In turn, relative heights can be used to interpret
objects.
In a similar fashion, relative depths can often be
interpreted.
Descriptions include tall, intermediate, and short; deep, intermediate, and
shallow.
49
51. Elements of Image Interpretation
Association:
This is very important when trying to interpret an object or
activity.
Association refers to the fact that certain features and activities
are almost always related to the presence of certain other
features and activities.
51
91. Application of RS and GIS
35
Agriculture and Soil
• Precision Agriculture,
Crop Acreage and
Production
Estimation, Soil and
Land Degradation
Mapping
Forest, Biodiversity
and Environment
• Forest Cover and
Type Mapping,
Biodiversity
Characterisation,
Environmental
Impact Studies,
Monitoring of
Environmental
Sensitive Area,
Monitoring of
Wetland Areas,
Forest Fire and Risk
Mapping
Engineering and
Geology
• Mineral Potential
Mapping,
Groundwater
Potential Zoning,
Infrastructure
Planning
Regional/ Land
Development
• Town and Country
Planning, Land
Alienation, Solid
Waste Disposal
91
92. Applicationof RS and GIS
36
Marine and
Oceanography
• Potential Fishing
Zone (PFZ),
Coastal Zone
Mapping, Marine
Resources,
Physical
Oceanography
Disaster
Management
• Monitoring and
Mapping of
Disaster Areas
(Forest fire,
Flood and
Landslide),
Landslide Hazard
Zonation, Flood
Damage
Assessment,
Forest Fire
Meteorology
• Extended Range
Monsoon
Forecasting,
Ocean State
Forecasting
Water
• Potential
Drinking Water
Zones,
Monitoring of
Catchment and
Reservoir Areas,
Surface Water,
Watershed
Development
92
93. Applicationof RS and GIS
37
Environmental Health
• Dengue Risk
Mapping Zoning,
Children Malnutrition
Study, Air Pollution
Study, Tick Borne
Disease
Landuse Monitoring
• Landuse/ Land Cover
Mapping, Wasteland
Mapping,
Topography and
Geographic
Positioning, Urban
Development,
Geology
National Security
• Intelligence,
Territorial Security
Management,
Mapping and Rescue
Planning, Strategic
and Tactical, Ground
Mobility
93
106. • BooksonRemotesensing
BooksandTutorials
55
James B. Campbell, Randolph H. Wynne (2011):Introduction to Remote Sensing, Fifth Edition
Canada Centre for Remote Sensing Fundamentals of Remote sensing
Thomas M. Lillesand (eds.), 2007. Remote sensing and image interpretation, Willey.
106
107. BooksandTutorials
Paul R. Wolf (eds.), 2000. Elements of photogrammetry with applications in GIS, McGraw-Hill Science.
Qihao Weng, Remote Sensing and GIS Integration, Theory, Methods and Applications
BooksonRemoteSensingand GIS
56
107
108. BooksandTutorials
• BooksonGIS
Shahab Fazal, GIS Basics
Michael N. DeMers, GIS for Dummies
Julie Delaney & Kimberly Van Niel, Geographic Information system An introduction
57
108
110. RemoteSensing (RS)
□ Remotelysensingtheuseful information of object (earth)
□ Processof recording, measuring and interpreting imagery and
digital representations of energy patterns derived from
noncontactsensor systems
GeographicInformation System(GIS)
□ Asystemdesigned to capture, store, manipulate, analyze,
manage, and present all types of geographically
referenced data
3
110
111. Geographically Referenced
image
Geographically Referenced Data
separate GIS from other
Information Systems.
Georeferencing means that the
internal coordinate system of an
image or aerial photo image can
be related to a geographic
coordinate system.
Georeference something means
to define its existence in physical
space. That is, establishing its
location in terms of coordinate
systems.
Before we begin discussing GIS,
we must understand data nature
used with GIS applications.
111
112. For example, roads-
To describe a road, we need locations
(where it is), and its characteristics: length,
name, speed limit, and direction).
The location, also called geometry or shape,
represents spatial data,
whereas the characteristics are attribute
data.
So, the road, like any other geographically
referenced data, has two main components:
spatial data & attribute data.
112
114. Can you recall
Google Earth?
The information in the Google earth is obtained
through Remote Sensing
While its representation and management on
geographical locations is made possible
through GIS
4
114
115. Can you recall
Google Earth?
Let's look at small movies about Google earth to
learn more about the remotely sensed
information and its geographical referencing of
the information
5
115
116. Google Earth Engine allows
observation of dynamic changes in
agriculture, natural resources, and
climate using geospatial data
from the Landsat satellite
program, which passes over the
same places on the Earth every
sixteen days.
116
117. Nitin Chauhan - Department of Remote Sensing
GEOGRAPHICAL
INFORMATION SYSTEM
117
118. Geography….
The Science of Earth’s Physical
features, resources, climate,
population etc.
Nitin Chauhan - Department of Remote Sensing 118
119. Geography….
What & Where
Location is important
What & Where
4
GEOGRAPHY = Geo + Graphy
SNAKES & LADDER
Nitin Chauhan - Department of Remote Sensing 119
120. E L
P P A
O G D
C A
T
Data…
5
Nitin Chauhan - Department of Remote Sensing 120
121. L E
G
D O
C A T
Information
6
A P P
Nitin Chauhan - Department of Remote Sensing 121
122. Data Information
Factual information,
especially information
organized for analysis
or used to reason or
make decisions.
Information is the
result of processing,
manipulating and
organizing data in a
way that adds to the
knowledge of the
person receiving it.
Data versus Information….
7
Nitin Chauhan - Department of Remote Sensing 122
123. Nitin Chauhan - Department of Remote Sensing
GIS
⚫ Geographic
GIS tend to deal primarily with geographic or spatialfeatures.
These objects can be referenced or related to a specific location in space.
⚫ Information
Large volumes of data, handled within a GIS
Real world objects with set of characteristics or descriptive attributes
⚫ System
Complex environments are broken down into their component parts for ease of
understanding and handling but
Are considered to from an integrated whole
123
124. What GIS can do? Real world problems
Identification Where ?
Locate What is there?
Optimum path What is the best route?
Patterns What relations exists between?
Trend What has changed ?
Models What if ?
What GIS can do???
9
Nitin Chauhan - Department of Remote Sensing 124
125. GIS Definition
⚫Toolbox based
- set of tools
- a system
- an information system
⚫Database definitions
- a database system in which most of the data are spatially indexed, and
upon which a set of procedures are operated in order to answer queries
about spatial entities in the database.
⚫Organization based definitions
- a decision support system involving the integration of spatially referenced
data in a problem solving environment
for capturing, storing, retrieving,
analyzing and displaying which
are spatially referenced to earth
Nitin Chauhan - Department of Remote Sensing 125
126. C + S + T + A + R + D = GIS
Defining GIS….the easy way
11
Nitin Chauhan - Department of Remote Sensing 126
127. GIS is a tool that can:
C = Collect
S = Store
Defining GIS….the easy way
12
T = Transform
A = Analyze
R = Retrieve
D = Display
d
Nitin
a
Cht
aua
han - Department of Remote Sensing
127
128. History of GIS
⚫ Ian L. McHarg is Known as “ Father of GIS”
⚫ 1963 : Canada Geographic Information System (CGIS) :
http://geogratis.cgdi.gc.ca/CLI/index_agriculture.html). It was given by Roger
Tomlinson to analyze Canada's national land inventory
⚫ 1964 : Harvard Laboratory for Computer Graphics (and Spatial Analysis) was
established by Howard Fisher. This lab had major influence on the development
of GIS until early 1980
⚫ 1965 : The development of the GBF-DIME (Geographic Base Files - Dual
Independent Map Encoding) files by the
U.S. Census Bureau. term DIME itself was first coined by
George Farnsworth
13
Nitin Chauhan - Department of Remote Sensing 128
129. History of GIS
⚫1966 : Howard Fisher developed
SYMAP (Synagraphic Mapping
a general-purpose
System)
mapping package, producing
• isoline, choropleth and proximal maps on a line
printer.
• 1966 : Howard Fisher developed SYMAP (Synagraphic
Mapping System) a general-purpose mapping package,
producing isoline, choropleth and proximal maps on a
line printer.
14
Nitin Chauhan - Department of Remote Sensing 129
130. History of GIS
⚫1969 : Data formats begin to emerge and private
vendors began offering GIS packages:
Environmental Science Research Institute (ESRI) is founded
by Jack and Laura Dangermond
Jim Meadlock establishes Intergraph Corporation (originally
called M & S Computing Inc)
⚫1972 : IBM's GFIS (Geographic Information
Systems)
15
Nitin Chauhan - Department of Remote Sensing 130
131. History of GIS
⚫ 1976 : Minnesota Land Management Information System
(MLMIS), developed at the Centre for Urban and Regional
Analysis, University of Minnesota.
⚫ 1977 : The USGS (U.S. Geological Survey) develops the
Digital Line Graph (DLG) spatial data format
⚫ 1978 : ESRI developed the first version of Arc/Info, the
current leading GIS software package.
⚫ 1978 : ERDAS (Earth Resource Data Analysis System) was
founded
16
Nitin Chauhan - Department of Remote Sensing 131
132. History of GIS
⚫ 1980 : GIS was pushed to evolve towards analysis
⚫ 1982 : ESRI's ARC/INFO® 1.0, the first commercially
available GIS software package, which ran on mainframe
computers
⚫ 1985 : Army Corps of Engineers at the Construction
Engineering Research Laboratory (CERL) started the
development of the GIS GRASS – Geographic Resources
Analysis Support System – as a raster based GIS
programme
17
Nitin Chauhan - Department of Remote Sensing 132
133. History of GIS
18
⚫ 1986 : Mapinfo was founded. ESRI's PC ARC/INFO® 1.0, the
first GIS software available for the personal computer, was
released
⚫ 1987 : SPANS( Spatial Analysis System) GIS and IDRISI by Clark
University.
⚫ 1988 : US bureau of Census „TIGER‟(Topographically Integrated
Geographic Encoding and Referencing) digital data products.
⚫ 1988 : The National Centre for Geographic Information and
Analysis (NCGIA) was established in the USA
Nitin Chauhan - Department of Remote Sensing 133
134. History of GIS
19
⚫ 1989 : ER Mapper was launched. Intergraph launched MGE (Modular
GIS Environment)
⚫ 1990 : Third phase of evolution : GIS became a real Management
Information System (MIS), and thus able to support decision making
processes
⚫ 1992 : Lebanon, decided to rebuild the entire nations electricity
network in GIS environment
⚫ 1993 : XEROX PARC Map Viewer : first Web-based interactive map
Viewer was developed by Steve Putz
⚫ 1994 : OGC (Open Geospatial Consortium ) was founded
Nitin Chauhan - Department of Remote Sensing 134
135. History of GIS
⚫ Beyond 2000 :
Mobile GIS
Location based services
Open access to satellite images (ex. Google Earth)
20
⚫ 1997 : Internet GIS –
( ArcIMS – Arcview Internet Map Server)
( Mapserver – Developed by University of Minnesota – open source)
Nitin Chauhan - Department of Remote Sensing 135
136. Geographical information systemsevolved from centuriesof mapmakingand thecompilation
of spatial data
HistoryandDevelopmentof GIS
31
Map prepared by Eratosthenes
The Greek mathematician, astronomer, and geographerEratosthenes (ca. 276 –
194B.C.) laid the foundations of scientific cartography
136
137. HistoryandDevelopmentof GIS
Ptolemy’s map of the world, about A.D. 150, republished in 1482. Notice the
use of latitude and longitude lines and the distinctive projection of this map
32
137
138. History and Developmentof GIS
Al-Idrisi’s map of the world, 1456. He completed a map of the known world in
the 12th century. Drawn with south at the top, this later example has been
inverted for easier viewing.
33
138
139. Components/ Elements of GIS
Application
Hardware
⚫ There are namely 5 components of GIS
People
Software
Data
Nitin Chauhan - Department of Remote Sensing 139
140. RS and GIS ofEarthResources
24
GIS
Data
Product
Interpre
tation Products Users
Electromagetic remote sensing of earth and its processing
Remote Sensing Sensing System
Geo referencing
Pictorial and
Numerical data
140
141. Geographic Information Systems (GIS)systemdesigned to capture, store,manipulate,analyze, manage,and
present all types of geographically referenced data
GISare computerizedsystemsdesigned for thestorage, retrieval and
analysisof geographically referenced data
GISusesadvanced analytical tools to explore at a scientificlevel the spatial relationships, patterns, and
processesof cultural, biological, demographic, economic,geographic, and physical phenomena
Unique capabilities of GIS
GISstoresrelated geographic features inseparate collectionsof files called map layers
Map layers canbe reusedeasily and assembledinto any numberof mapcompositionsand overlaid for
analysis
GeographicInformationSystem(GIS)
25
141
148. Unique capabilities of GIS
GIS stores related geographic features in separate collections of files
called map layers
Map layers can be reused easily and assembled into any number
of map compositions and overlaid for analysis
14
8
....KEEP TAKING NOTES....
149. GIS answers the following
Location: What is at...? Where is it?
Condition: Status of features?
Trends: What has changed since...?
Patterns: What spatial patterns exist?
Modeling: What if…?
14
9
151. Vector data
Map features
Vector data comprise Points (x & y) , lines (segment of arcs), polygons
(lines with same start & end points)
Data comprise explicit spatial coordinates
Feature attributes
Every feature has attributes (e.g. name,
• area, population)
Shape Name Class Pop2000 State
Point New York City 8,008,278 NY
Point Los Angeles City 3,694,820 CA
Point Chicago City 2,896,016 IL
Vector
data is
also
called
‘spaghet
ti’ data 151
152. Vector data
15
2
....KEEP TAKING NOTES....
Line feature comprises of two forms of point locations (vertices), which represent change
in direction of ARCS…
NODES which represent the start & end of arcs,
including locations where different arcs connect…
Vector data are divided into their SPATIAL component and ATTRIBUTE component.
Attribute linked to each spatial feature are stored using RELATIONAL DATABASE SYSTEM.
153. Raster Data
Stored electronic image or picture
taken as an aerial photograph or
satellite image
Composed of a rectangular array of
square cells, called pixels, with a
number in each cell representing the
solid color fill of that cell…
153
156. TOPOLOGY
Topology can be defined as “The mathematical study of objects
which are preserved through deformation, twistings and
stretchings.”
Operations concerned with connections between objects
are dependent on information about topological
relationships.
15
6
....KEEP TAKING NOTES....
158. GIS example
Identify polluting companies and their proximity to populations
in poverty, water features, or schools.
Start with
1. Databases
2. Map layers
15
8
....KEEP TAKING NOTES....
169. GIS applications
Engineering Civil engineering, surveying, property mapping
Business Site location, delivery systems, marketing, media and press, real
estate.
Defense/intelligen
ce
Military operations, geospatial intelligence
Government Federal, state, local, economic development, elections, urban
and regional planning.
Health Public health, health and human services, hospitals, managed
care, research.
Natural resources Agriculture, archaeology, climate change, conservation,
environmental management, forestry, marine and coast, mining,
petroleum, water resources.
Public safety Computer-Aided Dispatch, emergency/disaster management,
EMS, homeland security, law enforcement, fire protection,
wildfire management
Transportation Aviation, highways, logistics, railways, ports and maritime, public
transit
Utilities/communic
ations
Electric, gas, pipeline, telecommunications, water/wastewater
.8..5.KEEPTAKING NOTES....
169
173. Importance of Remote Sensing
Remote sensing makes it possible to collect data from dangerous or inaccessible areas, with growing relevance in
modern society.
It replaces slower, costly data collection on the ground, providing fast and repetitive coverage of extremely large
areas for everyday applications, ranging from weather forecasts to reports on natural disasters or climate change.
Remote sensing is also an unobstructive method, allowing users to collect data and perform data processing and
GIS analysis offsite without disturbing the target area or object.
Monitoring floods and forest fires, deforestation, polar bears, chemical concentrations, and earthquakes are just a
few cases in which geospatial remote sensing provides a global perspective and actionable insights that would
otherwise be unattainable.
173
174. Why Remote Sensing
SYSTEMATIC DATA
COLLECTION
INFORMATION ABOUT
THREE DIMENSIONS OF REAL
OBJECTS
REPEATABILITY GLOBAL COVERAGE
THE ONLY SOLUTION
SOMETIMES FOR THE
OTHERWISE INACCESSIBLE
AREAS.
MULTIPURPOSE
INFORMATION
174
175. Suppose you have a digital image which has a
radiometric resolution of 6 bits. What is the maximum
value of the digital number which could be represented
in that image?
175
176. Searchand InstallGoogle earth or UseGoogle Mapsto locate you home
Thepurposeisto get interaction with remotely sensed informationand its
processingusinginternetGIS systems
Noformal submissionisrequired. However,youhaveto report about your
interaction with Google earth or Google Map
Deadline:Innext class
Assignment
62
176
177. A Model…
A model is simply a means of representing “reality” and, spatial data models provide abstraction of
spatially referenced features in the real world.
Representation of real world is often divided into,
(1) Entities (distinct objects like points, locations, roads, admin boundaries)
(2) Fields (convey the idea of values of some property at all locations)
Objects that are well described as distinct entities are sensibly represented using the
VECTOR DATA MODEL.
Properties that tend to vary quite smoothly from place to place are
frequently represented using RASTER DATA MODEL.
Exceptions are isolines / contours / temperature elevation etc…
17
7
....KEEP TAKING NOTES....
178. What is GIS?
17
8
Geographic Information Systems
(GIS) are computerized systems
designed for the storage, retrieval
and analysis of geographically
referenced data
GIS uses advanced analytical tools
to explore at a scientific level the
spatial relationships, patterns, and
processes of cultural, biological,
demographic, economic,
geographic, and physical
phenomena