Basics of RS and GIS

Lecture on Dt. 16-02-2017 at
BMCET, Surat
Basics of Remote Sensing and
GIS
Bhasker V. Bhatt
PG in-charge (ME TCP) & Assistant Professor
Faculty of Civil Engineering
SCET, Surat
For the Students of Civil Engineering

...KEEP TAKING NOTES...
Outline
 Remote Sensing Defined
 Resolution
 Electromagnetic Energy (EMR)
 Types
 Interpretation
 Applications

Remote Sensing Defined
 Remote Sensing is:
 “The art and science of obtaining information
about an object without being in direct contact
with the object” (Jensen 2000).
 There is a medium of transmission involved.

 Environmental Remote Sensing:
 … the collection of information about Earth surfaces
and phenomena using sensors not in physical contact
with the surfaces and phenomena of interest.
 We will focus on data collected from an overhead
perspective via transmission of Electromagnetic
Radiation.

 Remote Sensing Includes:
 A) The mission plan and choice of sensors;
 B) The reception, recording, and processing of the
signal data; and
 C) The analysis of the resultant data.

Orbits
 Low Earth orbit (LEO): geocentric orbits with
altitudes from 160 to 2,000 km (100–1,240
miles).
 Medium Earth orbit (MEO): geocentric orbits
ranging in altitude from 2,000 km (1,240 miles)
to just below geosynchronous orbit at 35,786
kilometers (22,236 mi).
https://en.wikipedia.org/wiki/List_of_orbits

When a satellite reaches exactly 42,164 kilometers from the center of the Earth
(about 36,000 kilometers from Earth's surface), it enters a sort of “sweet spot” in
which its orbit matches Earth's rotation.

A satellites orbit the Earth in one of two basic types of orbit.
•Circular satellite orbit: For a circular orbit, the distance from the Earth remains
the same at all times.
•Elliptical satellite orbit: The elliptical orbit changes the distance to the Earth
•Geocentre: When satellites orbit the Earth, either in a circular or elliptical orbit, the
satellite orbit forms a plane that passes through the centre of gravity or geocentre of
the Earth.
Source: http://www.radio-
electronics.com/info/satellite/satellit
e-orbits/satellites-orbit-
definitions.php

Energy Source or Illumination (A)
Radiation and the Atmosphere (B)
Interaction with the Target (C)
Recording of Energy by the Sensor
(D)
Transmission, Reception, and
Processing (E)
Interpretation and Analysis (F)
Application (G)
Source: Canadian Centre for Remote Sensing
Remote Sensing Process Components / Principle of RS

Resolution
 All remote sensing systems have four types of
resolution:
 Spatial
 Spectral
 Temporal
 Radiometric

High vs. Low?
Spatial Resolution
Source: Jensen (2000)

Source: Jensen (2000)
Spectral
Resolution

Temporal Resolution
Time
July 1 July 12 July 23 August 3
11 days
16 days
July 2 July 18 August 3

Radiometric Resolution
6-bit range
0 63
8-bit range
0 255
0
10-bit range
1023
Every time an image is acquired on
film or by a sensor, its sensitivity to the
magnitude of the electromagnetic
energy determines the radiometric
resolution.
The radiometric resolution of an
imaging system describes its ability to
discriminate very slight differences in
energy.
The finer the radiometric resolution of
a sensor, the more sensitive it is to
detecting small differences in reflected
or emitted energy.
Source:
http://www.nrcan.gc.ca/node/9379#answer

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.

Whiz Quiz
 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?

Answer

Answer
The number of digital values possible in an image is equal
to the number two (2 - for binary codings in a computer)
raised to the exponent of the number of bits in the image
(i.e. 2# of bits).
The number of values in a 6-bit image would be equal to 26
= 2 x 2 x 2 x 2 x 2 x 2 = 64.
Since the range of values displayed in a digital image
normally starts at zero (0), in order to have 64 values, the
maximum value possible would be 63.

Electromagnetic Radiation

Electromagnetic Spectrum

Signature Spectra

Types of Remote Sensing
 Aerial Photography
 Multispectral
 Active and Passive Microwave and LIDAR

Aerial Photos
 Balloon photography
(1858)
 Pigeon cameras
(1903)
 Kite photography
(1890)
 Aircraft (WWI and
WWII)
 Space (1947)
Images: Jensen (2000)

Multispectral
 NOAA-AVHRR (1100 m)
 GOES (700 m)
 MODIS (250, 500, 1000 m)
 Landsat TM and ETM (30 – 60 m)
 SPOT (10 – 20 m)
 IKONOS (4, 1 m)
 Quickbird (0.6 m)

AVHRR (Advanced Very High
Resolution Radiometer) NASA
NOAA
National Oceanic
and Atmospheric
Administration

GOES (Geostationary Operational
Environmental Satellites) IR 4

MODIS (250 m) (Moderate Resolution
Imaging Spectro-radiometer)

Landsat TM
(False Color Composite)

SPOT (2.5 m)

QUICKBIRD (0.6 m)

IKONOS (4 m Multispectral)

IKONOS (1 m Panchromatic)

RADAR
(Radio Detection and Ranging)
Image: NASA 2005

LIDAR
(Light Detection and Ranging)
Image: Bainbridge Island,
WA courtesy Pudget Sound
LIDAR Consortium, 2005

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.

Jensen (2000)
Shape

 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.

Jensen (2000)
Shadow

 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).

Jensen (2000)
Tone and Color

 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).

Jensen (2000)
Texture

 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.

Jensen (2000)
Pattern

 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.

Height and Depth

 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.

Jensen (2000)
Association

Imaging Tools and Data
 Google Earth
 USGS Data
 Bhuvan (of ISRO)

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…
....KEEP TAKING NOTES.... 60

What is GIS?
 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
61....KEEP TAKING NOTES....

Tools for GIS
 Hardware
 Computer
 Digitizer
 Scanner
 Printer/Plotter
 Software
 Desktop GIS
 Internet GIS
 CAD Software
 Database Software
 Multimedia (photos, videos, 3D models)

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

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…?

Scale of GIS data
Global to local

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
‘spaghetti’
data

Vector data
 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.

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…
Raster grids are conceptually simple structures,
comprising square cells with numeric values or
classes attached to each cell..

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.

Topology

GIS example
 Identify polluting companies and their
proximity to populations in poverty, water
features, or schools.
 Start with
Databases
Map layers

Databases
Not easy to interpret

Data shown as GIS layers

Additional layers
Political features (municipalities)

Additional layers
Physical features (lakes, rivers, etc.)

Additional layers
Administrative data (schools)

Maps and tables are interactive
Identify features

Maps and tables are interactive
Select features

Advanced GIS functions
Proximity selections

Advanced GIS functions
 Buffers
 Select top polluting companies and show the number of schools
within 2 miles of these companies.

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

Thanks
Prof. Bhasker V. Bhatt
www.bvbhatt.com
+91-98258-35364
bhasker.bhatt@scet.ac.in
Content source credit courtesy is due, where not mentioned in specific:
Remote Sensing by Gregory Vandeberg; Dept. of Geography, University of North Dakota, USA
(Content created 21/10/2005)
and
GIS Tutorial 1 - Basic Workbook by Jay Loteria; Anne Connell (Content created 06/03/2010)

Basics of RS and GIS

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