1. Electromagnetic radiation interacts with the Earth's atmosphere and surface before reaching remote sensors. 2. The spectral reflectance properties of materials depend on their composition, with each object exhibiting a distinctive spectral signature across wavelength ranges. 3. The atmosphere absorbs and scatters electromagnetic radiation differently depending on wavelength, with "atmospheric windows" transmitting energy to the ground.

1. DEVASHISH NEGI AMIT KUMAR
160517 160510
G.B.P.I.E.T
PAURI, GARHWAL
Electromagnetic Radiation
and its use in Remote Sensing
1

2. UNDERSTANDING ELECTROMAGNETIC
RADIATION
• Time-varying wave that has both electrical and magnetic components
• is radiated by atomic particles at the source
• propagates through the vacuum of space at the speed of light
• interacts with the Earth's atmosphere
• interacts with the Earth's surface
• finally reaches the remote sensors where it interacts with various
optical systems and detectors
2

3. 3

4. SPECTRAL REFLECTANCE PROPERTIES
• EMR reflected, depends on the nature of the materials and
which portion of the EMR is being measured
• The nature of this reflected component over a range of
wavelengths is called spectral response patterns
4

5. 5

6. SPECTRAL SIGNATURE
• Every natural and artificial object reflects and emits EMR over a range
of wavelengths in its own chemical composition and physical state
• The distinctive reflectance and emission properties of objects are
called spectral signature
• Within some limited wavelength region, a particular object will
usually exhibit a diagnostic spectral response patterns that differs
from other objects
• each material on the earth would have a distinctive spectral response
pattern
6

7. SPECTRAL SIGNATURE
• The atmosphere essentially “closes
down” in certain portions of the
spectrum while “atmospheric
windows” exist in other regions that
transmit incident energy effectively
to the ground
• It is within these windows that
remote sensing systems must
function
7

8. ATMOSPHERIC WINDOWS
• relatively transparent wavelength regions of the atmosphere
• wavelengths at which EMR are partially or wholly transmitted
through the atmosphere
8

9. ELECTROMAGNETIC SPECTRUM
• total range of wavelengths is commonly referred to as the electromagnetic
spectrum
• Any matter with a body temperature greater than 0 K emits electromagnetic
energy. Therefore, it has a spectrum
• different chemical elements have different spectra, they absorb and reflect
spectral energy differently
• Each compound has a unique spectrum due to its unique molecular
structure
• This discriminate one matter from the other
9

10. 10

11. INTERACTION OF EMR WITH ATMOSPHERE
• EMR interacts with particles and gases in the atmosphere
• It can happen in 3 ways
1.Scattering
2.Absorption
3.Refraction
11

12. 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
• Depends upon
-Wavelength of the radiation
-Abundance of particles or gases
-Distance the radiation travels through the atmosphere
12

13. TYPES OF SCATTERING
• Rayleigh (or molecular) Scattering
• Mie (or non-molecular) Scattering
• Nonselective scattering
13

14. RAYLEIGH (OR MOLECULAR OR SMALL
PARTICLE) SCATTERING
• caused by oxygen and nitrogen molecules
• most influential at altitude above 4.5 km
• The amount of Rayleigh scattering is 1/(L)^4, L=wavelength
• As the result, invisible ultraviolet radiation is greatly affected by
Rayleigh scattering
• This explains why the clear sky appears blue
14

15. MIE (OR NONMOLECULAR OR LARGE
PARTICLE) SCATTERING
• Occurs when there are sufficient particles in the atmosphere that
have mean diameters from 0.1 to 10 times larger than the
wavelength under consideration
• influences longer radiation wavelengths than Rayleigh scattering
• agents include water vapor and tiny particles of smoke, dust, etc.
• Influence in the lower 4.5 km of the atmosphere
15

16. NONSELECTIVE SCATTERING
• Happened when the lower atmosphere contains suspended aerosols(dia. 10
times larger than wavelength)
• example - smoke, water vapor, water droplets, ice crystals in the clouds
and fog
• impacts on almost all spectral bands
• water droplets and ice crystals scatter all wavelengths equally well so that
the clouds in the sunlit sky looks white
• large smog particles cause the color of sky to grey
16

17. REMOTE SENSING
• science of acquiring information
about the objects of interest,
without actually being in contact
with it
• is done by sensing and recording
reflected or emitted energy and
processing, analyzing and applying
that information
17

18. USING EMR IN REMOTE SENSING
• Remote sensing devices detect EMR reflected from the Earth
surface
• Remote sensing device detect EMR emitted by the Earth itself
• Remote sensing devices generate their own EMR, bounce it off
the Earth’s surface and measure the EMR returned
18

19. SPECTRAL REFLECTANCE CURVE
• reflectance characteristics of earth surface feature may be
quantified by measuring the portion of incident energy
(Irradiance) that is reflected (Radiance)
• This energy is measured as a function of wavelength and is
called spectral reflectance
• A graph of spectral reflectance as a function of wavelength is
termed as spectral reflectance curve
19

20. SPECTRAL REFLECTANCE EXAMPLES
• Bare soil :
The surface reflectance from
bare soil depends on many
factors such as color,
moisture content, presence
of carbonate and iron oxide
content
20

21. SPECTRAL REFLECTANCE EXAMPLES
• Water:
• Longer wavelength visible and near infrared radiation is
absorbed more by water than shorter visible wavelengths
• 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
21

22. SPECTRAL REFLECTANCE EXAMPLES
22