Principles of remote sensing

• “The art, science, and technology of
obtaining reliable information about
physical objects and the environment,
through the process of recording,
measuring and interpreting imagery and
digital representations of energy
patterns derived from non-contact
sensor systems”.
• According to India’s National Remote
Sensing Agency- “Remote Sensing is
the technique of acquiring information
about objects on the earth’s surface
without physically coming into contact
with them”.
INTRODUCTION TO REMOTE SENSING

History of Remote Sensing
1859 - First aerial
photographer
1862 –
US Army balloon corp
1903 - The Bavarian
Pigeon Corps
1908 - First photos
from an airplane
1914-1918 –
World War I IGARSS 2013

• Detection and discrimination of objects or surface
features means detecting and recording of radiant energy
reflected or emitted by objects or surface.
• Different objects return different amount of energy in
different bands of the electromagnetic spectrum, incident
upon it.
• Depend upon the property of material (physical,
structural, and chemical), surface roughness, angle of
incidence , intensity , and wavelength of radiant energy.

1. Energy Source or Illumination (A)
2. Radiation and the Atmosphere (B)
3. Interaction with the Target (C)
4. Recording of Energy by the Sensor (D)
5. Transmission, Reception, and Processing (E)
6. Interpretation and Analysis (F)
7. Application (G)

 The first requirement for remote sensing is to have an energy source to
illuminate the target (unless the sensed energy is being emitted by the
target).
 This energy is in the form of electromagnetic radiation.

 Electromagnetic radiation is the energy source to illuminate the
target.
• Electromagnetic wave is consists of two fluctuating fields, they are an
electrical field (E) and a magnetic field (M). These two fluctuate at
right angle to one another, and both are perpendicular to the
direction of propagation.
• Relation between Wavelength and Frequency:
Wavelength and frequency are related by the following formula:
c = λv
where: λ = wavelength (m)
v = frequency (cycles per second, Hz)
c = speed of light (3x108 m/s)
1. Medium frequency -
2. High frequency -
shorter wavelength
3. Low frequency -
Higher wavelength
Wavelength

ElectromagneticSpectrum
 The Electromagnetic
spectrum is the continuum
of energy ranging from
kilometers to nanometers in
wavelength. This continuum
is commonly divided into the
following ranges, called
spectral bands, the
boundaries between them
being gradational.

• As the energy travels from its source to the
target, it will come in contact with and
interact with the atmosphere it passes
through.
• 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 occurs
when particles are very small
compared to the wavelength
of the radiation, e.g. small
specks of dust or nitrogen and
oxygen molecules.
 Rayleigh scattering causes
shorter wavelengths of energy
to be scattered much more
than longer wavelengths. This
is the dominant scattering
mechanism in the upper
atmosphere.


 Mie scattering occurs when the
particles are just about the
same size as the wavelength
of the radiation.
 Dust, pollen, smoke and water
vapour are common causes of
Mie scattering which tends to
affect longer wavelengths than
those affected by Rayleigh
scattering.
 Mie scattering occurs mostly in
the lower portions of the
atmosphere where larger
particles are more abundant,

 This occurs when the particles are much larger
than the wavelength of the radiation.
 Water droplets and large dust particles can
cause this type of scattering.
 Nonselective scattering gets its name from the
fact that all wavelengths are scattered about
equally.
 This type of scattering causes fog and clouds to
appear white to our eyes because blue, green,
and red light are all scattered in approximately
equal quantities (blue+green+red light = white
light).

 Absorption is the other main
mechanism at work when
electromagnetic radiation
interacts with the atmosphere.
 This phenomenon causes
molecules in the atmosphere to
absorb energy at various
wavelengths. Ozone, carbon
dioxide, and water vapour are
the three main atmospheric
constituents which absorb
radiation.

• Those areas of the frequency
spectrum which are not severely
influenced by atmospheric absorption
and thus, are useful to remote sensors,
are called atmospheric windows.
• 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.
• Because gases absorb
electromagnetic energy in very specific
regions of the spectrum, they influence
where (in the spectrum) we can "look"

 Radiation that is not
absorbed or scattered in
the atmosphere can reach
and interact with the
Earth's surface.
 There are three forms of
interaction that can take
place when energy strikes,
or is incident (I) upon the
surface:

Absorption (A) occurs when
radiation (energy) is absorbed
into the target.
Transmission (T) occurs when
radiation passes through a target.
Reflection (R) occurs when
radiation "bounces" off the target
and is redirected.

When a surface is smooth, we get specular or mirror-like
reflection where all (or almost all) of the energy is directed
away from the surface in a single direction.
Diffuse reflection occurs when the surface is rough and the
energy is reflected almost uniformly in all directions.
specular diffuse

• After the energy has been scattered by, or emitted from the
target, we require a sensor (remote - not in contact with the
target) to collect and record the electromagnetic radiation.

• The energy recorded by the sensor has to be transmitted,
often in electronic form, to a receiving and processing
station where the data are processed into an image
(hardcopy and/or digital).

• the processed image is interpreted, visually and/or digitally
or electronically, to extract information about the target
which was illuminated.

• Geology: geological mapping;
• Hydrology: monitoring wetlands and snow cover;
• Agriculture: crop type identification, crop condition
monitoring, soil moisture measurement, and soil tillage and
crop residue identification;
• Forestry: clear-cuts and linear features mapping, biomass
estimation, species identification and fire scar mapping;
• Oceanography: sea ice identification, coastal wind field
measurement, and wave slope measurement.
• Shipping: for ship detection and classification.
• Coastal Zone: for shoreline detection, substrate mapping, slick
detection and general vegetation mapping.
• Military/Security Applications: detecting or locating metal
objects.

• surficial deposit / bedrock mapping
• lithological mapping
• structural mapping
• sand and gravel (aggregate) exploration/ exploitation
• mineral exploration
• hydrocarbon exploration
• environmental geology
• geobotany
• baseline infrastructure
• sedimentation mapping and monitoring
• event mapping and monitoring
• geo-hazard mapping
• planetary mapping

• wetlands mapping and monitoring,
• soil moisture estimation,
• snow pack monitoring / delineation of extent,
• measuring snow thickness,
• determining snow-water equivalent,
• river and lake ice monitoring,
• flood mapping and monitoring,
• river /delta change detection
• drainage basin mapping and watershed modeling
• irrigation canal leakage detection
• irrigation scheduling

. ice concentration
· ice type / age /motion
· surface topography
· tactical identification of leads: navigation: safe shipping
routes/rescue
· ice condition (state of decay)
· pollution monitoring
· meteorological / global change research

• natural resource management
• · · baseline mapping for GIS input
• · urban expansion / encroachment
• · routing and logistics planning for seismic / exploration /
resource extraction
activities
• · damage delineation (tornadoes, flooding, volcanic,
seismic, fire)
• · legal boundaries for tax and property evaluation
• · target detection - identification of landing strips, roads,
clearings, bridges,
• land/water interface

Ocean pattern identification:
· wind and wave retrieval
· water temperature monitoring
· water quality
·Oil spill mapping and predicting oil spill extent and drift
strategic support for oil spill emergency response decisions
· identification of natural oil seepage areas for exploration
Shipping
· navigation routing
· traffic density studies
· near-shore bathymetry mapping

 Remote sensing technology has developed from balloon photography to
aerial photography & then advanced to multi-spectral satellite imaging.
 Radiation interaction characteristics of earth and atmosphere in different
regions of Electromagnetic spectrum are very useful for identifying and
characterizing earth and atmospheric features.
 Aircrafts and satellites are the main platforms used in the remote sensing.
 For measurements of the Earth's surface and depending on the wavelength
region examined, these properties can include factors such as roughness,
mineralogy, temperature, particle size, and elemental abundance.
 Remote sensing has become a widely accepted research tool by almost all
Geological Surveys the world over.
CONCLUSION

BOOKS
• Anji Reddy. M., (2001) Remote Sensing and Geographical
information Systems, Third Edition, BS. Publications,
Hyderabad.,Pp:24-54.
• Floyd F. Sabins.,(1996/1997) Remote Sensing principles and
Interpretation., W.H. Freeman And Company New york 3rd
Edition., Pp:29-236.
WEB SITES
• http://rst.gsfc.nasa.gov
• http://www.nrcan.gc.ca/sites/www.nrcan.gc.ca.earth-
sciences/files/pdf/resource/tutor/fundam/pdf/fundamentals
_e.pdf
• http://geography.huji.ac.il/personal/Noam%20Levin/1999-
fundamentals-of-remote-sensing.pdf

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Principles of remote sensing

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