This document provides an overview of remote sensing concepts. It defines remote sensing as acquiring information about an object without physical contact. Remote sensing data is collected from platforms like satellites and aircraft and analyzed. The document outlines the electromagnetic spectrum, how energy interacts with the atmosphere and objects, different sensor and image types, and resolutions. It also defines key terms like digital image, satellite imagery, spectral signature, and discusses different platform and sensor types used in remote sensing.

1. Completed By
Pallab Jana
M.Sc. in Remote Sensing & GIS
Vidyasagar University
Midnapore, 721102, West Bengal

2. BASIC CONCEPT OF
‘Remote Sensing’

3. Remote Sensing
Remote Sensing is the small or large scale acquisition of information of an object
phenomenon by the use of either recording or real time sensing device (s) that is not physical
or intimate contact with the object.
Remote Sensing is the acquisition of information about an object or phenomenon without
making physical contact with the object and thus in contrast to on-site observation,
especially the Earth. Remote sensing is used in numerous fields, including geography, land
surveying and most Earth science disciplines (for example, hydrology, ecology, meteorology,
oceanography, glaciology, geology); it also has military, intelligence, commercial, economic,
planning, and humanitarian applications.
Stages of Remote Sensing:
A) 1st Stage: Data Collection
B) 2nd Stage: Data Analysis

4. Application Areas or Relevance of Remote Sensing in Geography
A) Water Resource Management
i) Determination of Surface Water
ii) Determination of Ground Water
iii) Determination of Flood
iv) Water Pollution Detection
B) Forestry Application
C) Ocean and Coastal Monitoring
D) Atmosphere related Application
E) Agricultural Application
F) Wildlife Ecology Application
G) Environmental Degradation related Application
H) Application of Natural Disaster Assessment
I) Land Use And Land Cover Mapping
J) Urbanisation Related Application
K) Geology Related Application
L) Geomorphology Related Application

5. Advantages:
1. Fast Data Collection
2. Huge Area Cover
3. Revisable
4. Analysis by Computer
5. Multi purpose using
6. Save of Money & Time
7. Assumed storage of information
8. Receiving information in inaccessible places
Disadvantages:
1. Avoid of Small elements
2. Problem of differentiation
3. Gathering of Unwanted Data
4. Barrier of Cloudiness
5. Problem of Deep analysis
6. The initial cost is high
7. Need trained persons

6. Types of Remote Sensing
A) On the basis of Energy Source:
1) Active Remote Sensing
2) Passive Remote Sensing
B) On the basis of Wave length Regions:
1) Visible and Reflected infrared Remote Sensing (0.38-3μm)
2) Thermal infrared Remote Sensing (3μm-100μm)
3) Microwave Remote Sensing (1mm-1m)
C) On the basis of Method:
1) Aerial Photograph
2) Satellite Imagery

7. Electromagnetic Radiation (EMR)
Electromagnetic radiation (EM radiation or EMR) refers to the waves (or their quanta,
photons) of the electromagnetic field, propagating (radiating) through space, carrying
electromagnetic radiant energy. It includes radio waves, microwaves, infrared, (visible)
light, ultraviolet, X-rays, and gamma rays.
There are four main electromagnetic interactions:
 The force of attraction or repulsion between electric charges is inversely proportional to
the square of the distance between them.
 Magnetic poles come in pairs that attract and repel each other, much as electric charges
do.
 An electric current in a wire produces a magnetic field whose direction depends on the
direction of the current.
 A moving electric field produces a magnetic field, and vice versa.

8. Electromagnetic Spectrum (EMS)
Wave Band Wave Length
(Micro Meter)
Short
Wave
Cosmic Ray 0.000001
Gamma Ray 0.000001-
0.0001
X-Ray 0.0001-0.1
Ultra Violet (UV) 0.1-0.4
Visible Band 0.4-0.7
Blue: 0.4-0.5
Green: 0.5-0.6
Red: 0.6-0.7
Near-infrared (NIR) 0.7-1.3
Long
Wave
Middle Infrared 1.3-3
Thermal Infrared 3-14
Microwave 14-10^5
Radio-Wave &
Television Wave
10^5-10^8
The electromagnetic spectrum is
the range
of frequencies (the spectrum)
of electromagnetic radiation and
their
respective wavelengths and photon
energies.

9. Energy Interaction With the Atmosphere
Before radiation used for remote sensing reaches the Earth's surface it has to travel through
some distance of the Earth's atmosphere. Particles and gases in the atmosphere can affect
the incoming light and radiation. These effects are caused by the mechanisms of scattering
and absorption.
Types of Energy Interaction with the Atmosphere
A) Refraction
B) Absorption
C) Scattering
a) Rayleigh Scattering (0.4-0.7μm) (sky appears “blue”)
b) Mie Scattering (0.1-10μm) (sky appears “red”)
c) Non-Selective Scattering (>10μm) (sky appears “white”)
**Atmospheric Window:
One important practical consequence of the interaction of electromagnetic radiation with
matter and of the detailed composition of our atmosphere is that only light in certain
wavelength regions can penetrate the atmosphere well. These regions are called atmospheric
windows.

10. Short Questions
##Gray Value/Gray Level: The grey level or grey value indicates the brightness of a pixel.
##True Colour Composition (TCC): A natural or true color composite is an image
displaying a combination of the visible red, green and blue bands to the corresponding red,
green and blue channels on the computer display.
##False Colour Composition (FCC): False color images are a representation of a
multispectral image produced using any bands other than visible red, green and blue as the
red, green and blue components of the display.
## Standard False Colour Composition (SFCC): When FCC Globally followed.
## Vegetation Indices (VI): Different bands of a multispectral image may be combined to
accentuate the vegetated areas. One such combination is the ratio of the near-infrared band to
the red band. This ratio is known as the Ratio Vegetation Index (RVI).
##Black Body Radiation: Black-body radiation is the thermal electromagnetic radiation
within or surrounding a body in thermodynamic equilibrium with its environment, emitted by
a black body (an idealized opaque, non-reflective body). It has a specific spectrum of
wavelengths, inversely related to intensity that depend only on the body's temperature, which
is assumed for the sake of calculations and theory to be uniform and constant.
##Pixel: A pixel, or picture element is a physical point in a raster image, or the smallest
addressable element in an all points addressable display device; so it is the smallest
controllable element of a picture represented on the screen.

11. Interaction of EMR with the Object
A) Soil: Water can coat soil as in the image to the left. Light can reflect off multiple grains in
dry soil but when wet, water coats the grains and light is internally reflected and absorbed
reducing reflectance in visible and NIR. Soils are also darker in the far infrared where
water absorption is strong as explored in the vegetation section above.
B) Water: Longer wavelength visible and near infrared radiation is absorbed more by water
than shorter visible wavelengths. Thus water typically looks blue or blue-green due to
stronger reflectance at these shorter wavelengths, and darker if viewed at red or near infrared
wavelengths.
C) Snow: Snow reflects nearly all the yellow-green light from the sun, as do many bright
objects. Yet, the porous, white crystals also absorb mid-infrared wavelengths of light (light to
the right of red on the color spectrum).
D) Cloud: The material is opaque to incident Radiation a portion of EMR is converted to
heat (reradiated).
E) Vegetation: A chemical compound in leaves called chlorophyll strongly absorbs radiation
in the red and blue wavelengths but reflects green wavelengths.

12. Digital Image
Definition: A digital image is an image composed of picture elements, also known as
pixels, each with finite, discrete quantities of numeric representation for its intensity or gray
level that is an output from its two-dimensional functions fed as input by its spatial
coordinates denoted with x, y on the x-axis and y-axis, respectively. Depending on whether
the image resolution is fixed, it may be of vector or raster type. By itself, the term "digital
image" usually refers to raster images or bitmapped images (as opposed to vector images)
Characteristics.
Types of Digital Image:
1) Binary Image
2) Monospectral Image
3) Multispectral Image
4) Multi-Dimentional Image
5) Colour Image
Merits:
Demerits:

13. Satellite Imagery
Definition: Satellite imagery (also Earth observation imagery, spaceborne photography, or
simply satellite photo) are images of Earth collected by imaging satellites operated by
governments and businesses around the world. Satellite imaging companies sell images by
licensing them to governments and businesses such as Apple Maps and Google Maps. It
should not be confused for astronomy images collected by space telescope.
Types of Digital Image:
A) On the basis of Wave length
1) Visible and Reflected Infrared Image
2) Thermal Infrared Image
3) Microwave Image
B) On the basis of Source of Energy
1) Passive Remote Sensing Image
2) Active Remote Sensing Image
Segments of Satellite Imagery:
i) Space Segments
ii) Sensor System
iii) Ground Segments
Advantages:
1. Sympatic View
2. Revisable
3. Multipurpose
Disadvantages:

14. ##Spectral Signature/Spectral Reflectance: Spectral signature is the variation of
reflectance or emittance of a material with respect to wavelengths (i.e., reflectance/emittance
as a function of wavelength). The spectral signature of stars indicates the composition of the
stellar atmosphere. The spectral signature of an object is a function of the incidental EM
wavelength and material interaction with that section of the electromagnetic spectrum.
##Spectral Signature Curve: When Spectral Signature represent as a curve that called
Spectral Signature Curve.
**Spectral Library

15. Satellite
Definition: Satellite is an object that has been intentionally placed into orbit. These objects
are called artificial satellites to distinguish them from natural satellites such as Earth's Moon.
Characteristics: Characteristics
Types:
A) Natural Satellite: A natural satellite, or moon, is, in the most common usage, an
astronomical body that orbits a planet or minor planet (or sometimes another small Solar
System body).
B) Artificial Satellite: In the context of spaceflight, a satellite is an object that has
been intentionally placed into orbit. These objects are called artificial satellites to distinguish
them from natural satellites such as Earth's Moon.
1. Geostationary Satellite
2. Sun-Synchonous Satellite

16. Source of Energy
Definition: Many sources of electromagnetic radiation come from man-made technology. On
the other side of the spectrum, we have ultraviolet radiation, which is emitted by black lights
and fluorescent lamps. Of course, the main source of UV rays is the sun, which is also a
major source of X-rays.
Types of Energy Source:
A) Natural Source: The Sun is a common source of electromagnetic energy. It
radiates solar energy in all directions. Earth reflects the energy from the sun and emits some
energy in the form of heat.
b) Artificial Source: That provides its own source of electromagnetic energy. An active radar
sensor, whether airborne or spaceborne, emits microwave radiation in a series of pulses from
an antenna.

17. Sensor and Its Function
Definition: The sensor detects and measures the radiation that is reflected or backscattered
from the target.
Types of Sensor:
A) Image Forming Sensor
1. Active Sensor
2. Passive Sensor
B) Non-image Forming Sensor

18. Satellite Platform
Definition: Remote sensing means acquiring and measuring information about an object
or phenomenon via a device that is not in physical or direct contact with what is being
studied (Colwell, 1983).To collect remotely sensed data, a platform – an instrument that
carries a remote sensing sensor – is deployed. From the mid 1800’s to the early 1900’s,
various platforms such as balloons, kites, and pigeons carried mounted cameras to collect
visual data of the world below. Today, aircraft (both manned and unmanned) and satellites
collect the majority of remotely sensed data. The sensors typically deployed on these
platforms include film and digital cameras, light-detection and ranging (LiDAR) systems,
synthetic aperture radar (SAR) systems, and multi-spectral and hyper-spectral scanners.
Many of these instruments can be mounted on land-based platforms, such as vans, trucks,
tractors, and tanks. In this chapter, we will explore the different types of platforms and
their resulting remote sensing applications.
Types of Platform:
A. Ground Based Platform (on the Ground)
B. Air Based Platform (0-160KM)
C. Aeroplane & Helicopter
D. Space Based Platform (>160km)

19. Concept of Resolution
Definition: The resolution of remote sensed raster data can be characterized in
several different ways. It is nearly impossible to acquire imagery that has high
spatial, spectral, radiometric and temporal resolution. This is known as
Resolution Trade-off, as it is difficult and expensive to obtain imagery with
extremely high resolution. Therefore it is necessary to identify which types of
resolution are most important for a project.
Types of Resolution:
A) Spatial Resolution
B) Spectral Resolution
C) Temporal Resolution
D) Radiometric Resolution

20. Thank ‘Q’
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