UNIT- I
INTRODUCTION TO REMOTE SENSING

INTRODUCTION
• Remote sensing is the science and art of obtaining information
about an object, area, or phenomenon through the analysis of data
acquired by a device that is not contact with the object, area, or
phenomenon under investigation.
• The remotely collected data can be of many forms, including
variations in force distributions, acoustic wave distributions, or
electromagnetic energy distributions.

ELECTROMAGNETIC RADIATON &SPECTRUM
• EMR is a dynamic form of energy that propagates as wave motion at a velocity of c
= 3 x 10*10 cm/sec. The parameters that characterize a wave motion are
wavelength (λ), frequency (ν) and velocity (c) (Fig. 2). The relationship between
above is c = νλ
• Visible light is only one of many forms of electromagnetic energy. Radio waves,
ultraviolet rays, radiant heat, and X-rays are other familiar forms. All this energy is
inherently similar and propagates in accordance with basic wave theory.
• In remote sensing, it is most common to categorize electromagnetic waves by their
wavelength location within the electromagnetic spectrum. The most prevalent unit
used to measure wavelength along the spectrum is the micrometer ð Þ m . A
micrometer equals 13106m.

ELECTROMAGNETIC SPECTRUM

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• 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.
• Scattering occurs when particles or large gas molecules present in
the atmosphere interact with and cause the electromagnetic
radiation to be redirected from its original path. How much
scattering takes place depends on several factors including the
wavelength of the radiation, the abundance of particles or gases, and
the distance the radiation travels through the atmosphere. There
are three (3) types of scattering which take place.
• Rayleigh scattering
• Mie scattering
• Nonselective scattering
• Rayleigh scattering occurs when particles are very small compared to
the wavelength of the radiation
• Mie scattering occurs when the particles are just about the same
size as the wavelength of the radiation
• nonselective scattering occurs when the particles are much larger
than the wavelength of the radiation
INTERACTION WITH EARTH
SURFACE

CHARACTERISTICS OF
REMOTE SENSING
Characteristics of Remote Sensing
Remote sensing is characterised by;
Sensor Stage (satellite, plane, kite,
ground based)
View (angle of view)
Type of radiation
sensed(visible light,
infrared, radar)
Time of capture

TYPES OF SENSORS
• Remote sensing instruments are of two
primary types—
• ACTIVE SENSORS, provide their own
source of energy to illuminate the
objects they observe. An active sensor
emits radiation in the direction of the
target to be investigated. The sensor
then detects and measures the radiation
that is reflected or backscattered from
the target.
• PASSIVE SENSORS, on the other hand,
detect natural energy (radiation) that is
emitted or reflected by the object or
scene being observed. Reflected sunlight
is the most common source of radiation
measured by passive sensors

REMOTE SENSING PLATFORMS
Remote sensing platforms can be classified as follows, based on the elevation from
the Earth’s surface at which these platforms are placed.
Ground level remote sensing
o Ground level remote sensors are very close to the ground
o They are basically used to develop and calibrate sensors for different features on
the Earth’s surface.
Aerial remote sensing
o Low altitude aerial remote sensing
o High altitude aerial remote sensing
Space borne remote sensing o
Space shuttles
o Polar orbiting satellites
o Geo-stationary satellite

AIRBORNE AND SPACEBORNE REMOTING SENSING
• In airborne remote sensing, downward or sideward looking sensors mounted on aircrafts are used to
obtain images of the earth's surface. Very high spatial resolution images (20 cm or less) can be
obtained through this. However, it is not suitable to map a large area. Less coverage area and high
cost per unit area of ground coverage are the major disadvantages of airborne remote sensing.
While airborne remote sensing missions are mainly one-time operations, space-borne missions offer
continuous monitoring of the earth features.
• LiDAR, analog aerial photography, videography, thermal imagery and digital photography are
commonly used in airborne remote sensing.
• In space-borne remote sensing, sensors mounted on space shuttles or satellites orbiting the Earth
are used. There are several remote sensing satellites (Geostationary and Polar orbiting) providing
imagery for research and operational applications. While Geostationary or Geosynchronous
Satellites are used for communication and meteorological purposes, polar orbiting or sun-
synchronous satellites are essentially used for remote sensing.
• The main advantages of space-borne remote sensing are large area coverage, less cost per unit
area of coverage, continuous or frequent coverage of an area of interest, automatic/ semiautomatic
computerized processing and analysis. However, when compared to aerial photography, satellite
imagery has a lower resolution. Landsat satellites, Indian remote sensing (IRS) satellites, IKONOS,
SPOT satellites, AQUA and TERRA of NASA and INSAT satellite series are a few examples.

IMAGE DATA CHARACTERSTICS
• The most significant characteristic of the image data in a remote
sensing system is the wavelength, or range of wavelengths, used in the
image acquisition process. If reflected solar radiation is measured
images can, in principle, be recorded in the ultraviolet, visible and near-
to-middle infrared range of wavelengths.
DIGITAL IMAGE DATA FORMATS
• In order to properly process remotely sensed data, the analyst must
know how the data is organized and stored on digital tapes and how the
data are processed by computers and software
• There are four major data formats used by government and commercial
data suppliers:
• 1 Band Interleaved by Pixel (BIP) Format
• 2 Band Interleaved by Line (BIL) Format
• 3 Band Sequential (BSQ) Format

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BAND INTERLEAVED BY
PIXEL FORMAT (BIP)
One of the earliest digital
formats used for satellite data
is band interleaved by pixel
(BIP) format. This format
treats pixels as the separate
storage unit. Brightness
values for each pixel are
stored one after another. It is
practical to use if all bands in
an image are to be used.
BAND INTERLEAVED BY
LINE FORMAT (BIL)
Just as the BIP format treats each
pixel of data as the separate unit,
the band interleaved by line (BIL)
format is stored by lines. Below
Fig shows the logic of how the
data is recorded to the computer
tape in sequential values for a four
band image in BIL format. Each
line is represented in all four
bands before the next line is
recorded. Like the BIP format, it is
a useful to use if all bands of the
imagery are to be used in the
analysis. If some bands are not of
interest, the format is inefficient if
the data are on tape, since it is
necessary to read serially past
unwanted data
BAND SEQUENTIAL(BSQ)
FORMAT
The band sequential format
requires that all data for a single
band covering the entire scene be
written as one file (see Fig. 2-3.3).
Thus, if an analyst wanted to
extract the area in the center of a
scene in four bands, it would be
necessary to read into this
location in four separate files to
extract the desired information.
Many researchers like this format
because it is not necessary to read
serially past unwanted information
if certain bands are of no value,
especially when the data are on a
number of different tapes.
Random-access optical disk
technology, however, makes this
serial argument obsolete

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BAND INTERLEAVED
BY PIXEL FORMTA
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BAND SEQUENTIAL
FORMAT
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CARTOSAT
The name cartosat is a combination of
cartography and satellite. The cartosat
satellites are a series of Indian optical earth
observation satellites. The are used for
earths resource management defence service
and monitoring.
• Orbit : circular sun synchronous
• Nominal Wait Time to Acquire Adjacent
Path :11 days
• Orbital Repetivity Cycle : 126 days
• Local Time of Equator crossing : 10.30 a.m.
• Number of Orbits per day : 15
• Orbit period : 97 min
• Orbit inclination : 98.87°
• Orbit height : ~618 km
RADAR IMAGING SATELLITE is a series
of radar imaging reconnaissance satellites
built by ISRO. They provide all weather
earth observation satellites from ISRO.
• Regime : Sun-synchronous
• Apogee altitude : 536.38 km
• Inclination : 97.554 degrees
• Period : 95.49 minutes
• Mean motion : 14
• The revisit period is 25 days with an
advantage of a12 day inner cycle in the
CRS (Coarse Resolution ScanSAR) mode
RISAT

MODIS
• The Moderate Resolution Imaging
Spectroradiometer (MODIS) is a playload imaging
sensor built by Santa Barbara Remote Sensing that
was launched into earth orbit by NASA in 1999. With
its low spatial resolution but high temporal resolution,
MODIS data are useful to track changes in the
landscape over time. Examples of such applications are
the monitoring of vegetation health by means of time-
series analyses with vegetation indices, long term land
cover changes (e.g. to monitor deforestation rates),
global snow cover trends,] water inundation from
pluvial, riverine, or sea level rise flooding in coastal
areas,[ change of water levels of major lakes such as
the Aral see, and the detection and mapping
of wildland fires.
• Orbit : 705 km, 10:30 a.m. descending node (Terra) or
1:30 p.m. ascending node (Aqua), sun-synchronous,
near-polar, circular.
• Inclination : 98.2°
• Repetitive cycle : 16 days.
ADVANCED SPACEBORNE THERMAL EMISSION AND
REFLECTION RADIOMETER is a global digital
evaluation model V002 with 30 m reduction was used to
extract information on terrain surface and drainage
network at the micro-catchment. ASTER satellite image
data contribute to a wide array of global change
related application areas including the dynamics of
vegetation and ecosystems monitoring of harzards,
geology and soils land surface climatography, hydrology
glacier changes, land cover change and the generation of
digital elevation models(DEMs).
• Altitude : 705km
• Orbit : polar sun synchronous
• Repetitive cycle : 16 days
• Inclination : 98.3°
• Equator crossing time : 10:30AM (north to south)
ASTER

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IRS
INDIAN REMOTE SENSING
SATELLITE is designed to extract
information on natural resources
IRS has a wide range of applications
such as agricultural and inventory of
forest resources, geological
mapping, water resource
Orit : sun synchronous
Altitude : 904km
Inclination : 99.03°
Repetitive cycle : 22 days
LANDSAT
Land remote sensing satellite is the
first generation satellite which can
record the visible and near visible
wavelengths around the ground.
Altitude of 570 miles to gather
information on earth resource in a
systematic and repetitive manner
RBV, MSS, TM sensors are used.
Inclination : 99.09°
Repetitive cycle : 18,16 days.
Applied in agriculture forestry civil
engineering and land resources.
SPOT
Satellite Pour l’Observation de la
Terre also caleed as satellite for
earth observation with high
resolution. High resolution images
are being captured by spot which
are used for many application like
urban planning and growth
assessment, planning and growth
assessment planning for
transportation and extration for
natural resources.
Orbit : Sun-Synchronous
Altitude : 832 km
Inclination : 98.7°
Equatorial crossing time : 10:30 hrs
Repetitive cucle : one for every 26
days.