REMOTE

SENSING

)
 Natural Remote Sensing

Analysis

Sensing / Perceiving

Information / Knowledge

Boy or Man ?
 Artificial Remote Sensing

Analysis

Sensing / Perceiving

Extracting Information /
Knowledge

Output
Subject
 Definition of Remote Sensing
 Remote sensing is art, science & technology adopted for obtaining reliable
information of the objects on the surface of earth without coming into
physical contact. In fact we are measuring and recording the electro-
magnetic radiations reflected and emitted by the bodies.

 Major objective is to Analyze/Understand the Environmental and Natural

resources information.
 Components of RS
Sensor

Energy Source

Radiation

Atmosphere

Ground Acquisition centers/

Receivers

Output to Clients

Target area
Interpretation/ Analysis
 Electro Magnetic Radiation
Sun is the main source of energy.
Energy propagates in form of Electro Magnetic Radiation
(EMR).

Wavelength (λ)
Frequency (ν) c = ν* λ
Velocity (C)
 Electro Magnetic Spectrum
 Light energy is explained as EMR and can be classified according to the
length of the wave. All possible energy channels called as Electro Magnetic
Spectrum (EMS).

 Human eyes can only measure visible light but sensors can measure other
portions of EMS.

Figure: Electro Magnetic Spectrum (EMS)

 Sensors
Sensors are the devices, which gathers energy and converts it
into a signal and presents it in form suitable for obtaining
information about the target under investigation (Aggarwal, S.
2003).

Types of Sensors
PASSIVE
ACTIVE
- Depends on External energy,
- Creates their own energy
Sun, fire etc
- Work day & night
- Work on day
- Non seasonal
- Seasonal
Ex: Radar, LIDAR
Ex: Latsat, LISS, Spot & AWIFS
 RADARSAT (Active Sensor)

- Canadian Space Agency

- Altitude: 798 KM
- Inclination: 98.6°
- Orbit: Polar
- Orbit period: 100.7’
- Revisit time: 14 days

Image Credit: http://www.asc-csa.gc.ca

LISS III (Passive Sensor)
- ISRO - NRSC
- Altitude: 817 KM
- Inclination: 98.7°
- Orbit: Polar
- Orbit period: 101.35’
- GSD : 23.5 m
- Revisit time: 24 days

Image Credit: NRSC

 Platforms
Platforms are the places where the sensors are placed.
Depending upon the working environment they are classified as follow:

Cherry
based
Fixed
Platforms
Tripod based

Balloon
Platforms
Based
Air Borne
Aircraft
Moving
Platforms
Geo
Stationary
Space Borne
Sun
Synchronous
 Type of Space Borne Platform
Geo Stationary Platform Sun Synchronous Platform
• Faces towards particular portion • Crosses particular place at same local
of earth time
• 3600 km altitude • 600 - 900 km altitude

• West to East rotation • North to South rotation

• Equatorial Orbit • Polar Orbit

• Angular Coverage 120° • Inclination 80 °/100 ° to Equa.

• Orbital period 24 Hr. • Orbital Period 100’ (Approx.)

• Ex: INSAT, GSAT, etc … • Ex: IRS, LandSat, Spot etc …

 Types of Remote Sensing
Type of RS

Depending upon Depending upon Depending upon

energy source Sensor Platform
(EMR)

Active Passive

Ground
Air Borne
Base

Optical X-Ray IR or Thermal Microwave

 Optical Remote Sensing
• In Optical Remote Sensing, optical sensors detect solar radiation reflected
or scattered from the earth, forming images resembling photographs taken by
a camera high up in space.

• The wavelength region usually extends from (300 nm to 3000 nm)

the visible and near infrared (commonly abbreviated as VNIR) to
the short-wave infrared (SWIR).

• Different materials such as water, soil, vegetation, buildings and roads reflect
visible and infrared light in different ways. They have different colours and
brightness when seen under the sun.

• The interpretation of optical images require the knowledge of the spectral

reflectance signatures of the various materials (natural or man-made)
covering the surface of the earth.
 Thermal Infrared Remote Sensing
• There are also infrared sensors measuring the thermal infrared radiation
emitted from the earth, from which the land or sea surface temperature can
be derived.

• The middle-wave infrared (MWIR) and long-wave infrared (LWIR) are

within the thermal infrared region.

• The wavelength range of 3000 nm to 5000 nm and 8000 nm to 14000 nm.

These radiations are emitted from warm objects such as the Earth's surface.

• Thermal Infra RS used for measurements of the earth's land and sea surface
temperature and forest fire.
 Microwave Remote Sensing
 These satellites carry their own "flashlight" emitting microwaves to
illuminate their targets and Analyzes the information collected by the sensor.

 The active sensors emit pulses of microwave radiation to illuminate the

areas to be imaged. A microwave remote sensor records the backscattered
microwaves from earth or sea surface.

 The Microwave wavelength range of 1 mm to 1 m of electromagnetic

spectrum. So, have an additional advantage as they can penetrate clouds.

 Most of the microwave sensors are active sensors, having there own sources
of energy. Thus, images can thus be acquired day and night.
 Characteristics of Sensors

 Atmospheric Windows
 Spectral Resolution
 Spatial Resolution
 Radiometric Resolution
 Temporal Resolution
 Atmospheric Windows
 The spectral Bands for which the atmosphere is transparent are called
as the Atmospheric windows.
 Spectral Resolution
 The ability of a sensor to discriminate b/w different wavelengths in the
detected signals.
 RS sensors can have spectral resolution from more than 1µm to 1 nm.

Low Resolution Medium High Resolution

Resolution
Panchromatic Multi-Spectral (MS) Hyper-Spectral
(HS)
Single Band >1, <20 bands >= 20 bands
CartoSat P5 LISS-III, LandSat AVIRIS, Hyperion
 Four Band:
Spectral Resolution 0.52-0.59 (green)
0.62-0.68 (red)
Single Band: PAN
0.77-0.86 (near IR)
500 - 750 nm Panchromatic Multi-Spectral 1.55-1.70 (mid-IR)

CartoSat 1: Hyperion:
Band F image showing Katraj, Pune Image showing Katraj, Pune
 Spatial Resolution
 A measure of the smallest distance between two objects that can be
distinguished by a sensor.

Orbview : BVU (1 metre ) LISS III: BVU (23.5 metre )

Image Credit: NRSC
Image Credit: USGS

Source: Rees, 1999

0.6 m Spatial Resolution Hyper spectral Space Image
 Radiometric Resolution
 Radiometric resolution is a measure of sensor sensitivity to the magnitude of
the EMR.
 Finer the radiometric resolution greater the ability to detect the small diff. in
reflected/ emitted energy.
 Digital resolution is a synonym to Radiometric resolution. It is the number of
bits comprising the each image.

Radiometric Resolution

1 bit = 21 = 2 = {0, 1}
8 bit = 28 = 256 = {0,1,……….,255}
10 bit = 210 = 1024 = {0,1,……………………..,1023}
 Temporal Resolution
 Is the revisit time period of sensor to image the same area at the same
viewing angle.
 Multi temporal Remote sensing

Kedarnath
Floods
(June 2013)

Image Credit: NRSC

Pre Post
 Spectral Reflectance Curve
 Is the plot between the Spectral reflectance (ratio of reflected energy to
incident energy) and wave length.
 It depends upon the Chemical composition and Physical conditions.

Typical Spectral reflectance curve for Vegetation, Water & Soil

Image Credit: Dr Robert Sanderson
 How the Object is Identified by Sensor?
 The Basic principle of Remote Sensing is that each object reflect and emit
energy of particular part of EMR in a unique way. Therefore, the signatures
received from different objects is always different. This is called its Spectral
signature. This is the key for interpretation in RS.
 Viewing images
Three bands are viewable simultaneously

Monitor
Part of color guns
spectrum
Band
Blue 14
Green
Band
Red
253
NIR
SWIR Band
32
 Land use
pattern
Urban
Pollution planning
monitoring

Biodiversity
Hydrology
conservation

Applications
Ocean & Surveying and
coastal of mapping
monitoring RS

National
Agriculture Security

Environment
Geology al Science
Forestry
 Application of Remote Sensing
Agricultural Forestry
 Crop type classification.  Forest cover and density mapping
 Crop condition assessment.  Deforestation mapping
 Forest fire mapping.
 Crop yield estimation.
 Grassland mapping
 Crop stress monitoring.  Shifting cultivation
 Crop production forecasting  Wetland mapping and monitoring
 Mapping of soil characteristic.  Biomass estimation
 Soil moisture estimation.  Species inventory

National Security
Ocean applications:  Targeting
 Storm forecasting.  Disaster mapping and monitoring
 Water quality monitoring.  Damage assessment
 Weapons monitoring
 Aquaculture inventory and monitoring.
 Homeland security
 Navigation routing.
 Navigation
 Coastal vegetation mapping.  Policy
 Oil spill.
 Application of Remote Sensing

Hydrology: Urban Planning:

 Watershed mapping and management  Land parcel mapping

 Flood delineation and mapping  Infrastructure mapping

 Ground water targeting  Land use change detection

 Assessment of land surface water  Future urban expansion planning

 Assessment of sub surface water

 Snow melt run-off Geology:
 Multipurpose river valley  Lithological mapping
 Mineral exploration

Land Use/Land Cover mapping:  Environmental geology

 Natural resource management  Sedimentation mapping and monitoring

 Wildlife protection  Geo-hazard mapping

 Encroachment  Glacier mapping