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1. INTRODUCTION 1
2. WHAT IS REMOTE SENSING? 1
3. TYPES OF REMOTE SENSING 2
3.1. Satellite Remote Sensing 3
3.2. Optical and Infrared Remote Sensing 4
3.3. Microwave Remote Sensing 5
4. APLLICATIONS OF REMOTE SENSING 6
5. IMPORTANCE OF REMOTE SENSING 7
6. ADVANTAGES OF REMOTE SENSING 7
7. DISADVANTAGES OF REMOTE SENSING 8
8. CONCLUSION 8
9. BIBLIOGRAPHY 9
Remote sensing is the art and science of recording, measuring, and analysing
information about a phenomenon from a distance. Humans with the aid of their eyes, noses,
and ears are constantly seeing, smelling, and hearing things from a distance as they move
through an environment.
Thus, humans are naturally designed to be remote sensors. In order to study large areas
of the Earth’s surface geographers use devices known as remote sensors. These sensors are
mounted on platforms such as helicopters, planes, and satellites that make it possible for the
sensors to observe the Earth from above.
In this report, I will mainly focus on basic meaning or technical definition of remote
sensing, different types of remote sensing, applications, need for remote sensing, advantages
2.WHAT IS REMOTE SENSING?
Remote sensing is science of acquiring, processing, and interpreting images and related
data that are obtained from ground based, air or space borne instruments that record the
interaction between matter (target) and electromagnetic radiation.
Remote sensing uses the electromagnetic spectrum to image the land, ocean, and atmosphere.
In remote sensing, the sensors are not in direct contact with the objects or events being
observed. The information needs a physical carrier to travel from the objects/events to the
sensors through an intervening medium. The electromagnetic radiation is normally used as an
information carrier in remote sensing. The output of a remote sensing system is usually an
image representing the scene being observed. A further step of image analysis and
interpretation is required in order to extract useful information from the image.
Fig:1 -Process of remote sensing by satellite by receiving signals
3.TYPES OF REMOTE SENSING
There are mainly three types of remote sensing technique. They are
Satellite Remote Sensing
Optical and Infrared Remote Sensing
Microwave Remote Sensing
3.1. SATELLITE REMOTE SENSING
In satellite, remote sensing of the earth, the sensors are looking through a layer of
atmosphere separating the sensors from the Earth's surface being observed. Hence, it is
essential to understand the effects of atmosphere on the electromagnetic radiation travelling
from the Earth to the sensor through the atmosphere. The atmospheric constituents cause
wavelength dependent absorption and scattering of radiation. These effects degrade the quality
of images. Some of the atmospheric effects can be corrected before the images are subjected
to further analysis and interpretation.
Fig:2-Satellite remote sensor image
A consequence of atmospheric absorption is that certain wavelength bands in the
electromagnetic spectrum are strongly absorbed and effectively blocked by the atmosphere.
The wavelength regions in the electromagnetic spectrum usable for remote sensing are
determined by their ability to penetrate atmosphere. These regions are known as the
atmospheric transmission windows. Remote sensing systems are often designed to operate
within one or more of the atmospheric windows. These windows exist in the microwave region,
some wavelength bands in the infrared, the entire visible region and part of the near ultraviolet
regions. Although the atmosphere is practically transparent to x-rays and gamma rays, these
radiations are not normally used in remote sensing of the earth.
3.2. OPTICAL AND INFARRED 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 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 requires the knowledge of the spectral
reflectance signatures of the various materials (natural or man-made) covering the surface of
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.
Fig:3-Black and white image from optical remote sensor
3.3. MICROWAVE REMOTE SENSING
There are some remote sensing satellites which carry passive or active microwave
sensors. The active sensors emit pulses of microwave radiation to illuminate the areas to be
imaged. Images of the earth surface are formed by measuring the microwave energy scattered
by the ground or sea back to the sensors. These satellites carry their own "flashlight" emitting
microwaves to illuminate their targets. The images can thus be acquired day and night.
Microwaves have an additional advantage as they can penetrate clouds. Images can be acquired
even when there are clouds covering the earth surface.
A microwave imaging system which can produce high resolution image of the Earth is
the synthetic aperture radar (SAR). The intensity in a SAR image depends on the amount of
microwave backscattered by the target and received by the SAR antenna. Since the physical
mechanisms responsible for this backscatter is different for microwave, compared to
visible/infrared radiation, the interpretation of SAR images requires the knowledge of how
microwaves interact with the targets.
Fig:4-Process of microwave remote sensing
Fig:5-Microwave remote sensor image of Death Valley,
California and surrounding mountains.
APLLICATIONS OF REMOTE SENSING
Laser and radar altimeters on satellites have provided a wide range of data. By
measuring the bulges of water caused by gravity, they map features on the seafloor to
a resolution of a mile or so. By measuring the height and wavelength of ocean waves,
the altimeters measure wind speeds and direction, and surface ocean currents and
Ultrasound (acoustic) and radar tide gauges’ measure sea level, tides and wave direction
in coastal and offshore tide gauges.
Light detection and ranging (LIDAR) is well known in examples of weapon ranging,
laser illuminated homing of projectiles. LIDAR is used to detect and measure the
concentration of various chemicals in the atmosphere, while airborne LIDAR can be
used to measure heights of objects and features on the ground more accurately than
with radar technology. Vegetation remote sensing is a principal application of LIDAR.
Radiometers and photometers are the most common instrument in use, collecting
reflected and emitted radiation in a wide range of frequencies. The most common are
visible and infrared sensors, followed by microwave, gamma ray and rarely, ultraviolet.
Stereographic pairs of aerial photographs have often been used to make topographic
maps by imagery and terrain analysts in trafficability and highway departments for
potential routes, in addition to modelling terrestrial habitat features.
Surface Temperature: Sea or lake surface temperature (SST or LST) is derived from
satellites orbiting the earth. One such useful device is NOAA's (National
Oceanographic and Atmospheric Administration) AVHRR or Advanced Very High
IMPORTANCE OF REMOTE SENSING
Remote sensing makes it possible to collect data on dangerous or inaccessible areas.
Remote sensing provides real time updates, and does not require active human
assistance (i.e. you can collect data at any time, at any frequency, as long as the
equipment allows it).
Remote sensing can detect things that are not normally present in the visible spectrum
for example, temperature, or by detecting landforms underneath the surface of the
ground or ocean.
Remote sensing can scan large areas of land by satellite much more quickly than a
ADVANTAGES OF REMOTE SENSING
Provides data of large areas
Provides data of very remote and inaccessible regions
Able to obtain imagery of any area over a continuous period of time through which
the any anthropogenic or natural changes in the landscape can be analysed
Relatively inexpensive when compared to employing a team of surveyors
Easy and rapid collection of data
Rapid production of maps for interpretation
DISADVANTAGES OF REMOTE SENSING
The interpretation of imagery requires a certain skill level
Needs cross verification with ground (field) survey data
Data from multiple sources may create confusion
Objects can be misclassified or confused
Distortions may occur in an image due to the relative motion of sensor and source
Remote sensing is a technology with lot of applications. The emerging of this
technology help us to find earths image from a satellite. This technology is used to find the
images of other planets. The improvement of this technology helps the space scientists, military
for monitoring places. As remote sensing refers to the activities of observing/perceiving objects
or events at faraway places, the development of this technology will also help the agricultural
field, forest mapping and finding soil erosion. Thus, remote sensing is indeed a good
technology with many applications.