1. Basic Science in Remote Sensing
Basic radiation physics
EMR in the atmosphere (to be explained later)
Interactions of EMR with targets (to be explained later)
spectral reflectance
geometric effects

3. Electromagnetic Radiation

4. What is Light?

5. What is Color?

6. Units and Dimensions The SI System
Dimension Unit Symbol(s)
Length Meter/Micrometer (m, μm)
Area Square meter (m2)
Volume Cubic meter (m3)
Mass gram (g)
Time second (s)
Temperature Kelvin (K)
Energy joule (j)
Velocity meter/second (m/s)
Power Joule/second (watt) (j/s)
Energy Flux Density watt/square meter (W/m2)

7. What is EMR? - Two theories
Wave theory
Particle theory

8. Wave theory
In the 1860s, James Clerk Maxwell ( ) conceptualized electromagnetic radiation as an electromagnetic wave that travels through space at the speed of light, c, which is 3 x 108 m/s.
EM wave consists of two fluctuating fields
-Electric
-Magnetic
- Hence the terminology electromagnetic.
- The two vectors are at right angles to one another
- Both are perpendicular to the direction of travel.

9. Electromagnetic Wave

10. Terms Crest : The highest point of the wave.
Trough : The lowest point of the wave.
Amplitude : The height of the wave as measured to the trough or crest.
Wavelength : The distance between two nearest identical points on the wave in meters.
Frequency : The number of peaks passing a point in a set period of time.

11. Electromagnetic Waves

12. Electromagnetic Waves
A wave is characterized by two principal measures:
wavelength (λ) -- distance (in µm) between successive wave crests
frequency (ν) is the number of peaks passing a point per second (in Hertz, hz)

13. Wavelength vs. Frequency
Low
Long
Short
High

14. Wavelength and Frequency
Wavelength and frequency are related by the following formula:

15. Electromagnetic Spectrum: Distribution of Radiant Energies

16. Gamma Rays Very high energy, more penetrating than X-rays.
Generated by nuclear processes.
Some applications in medical imaging

17. X-Rays High energy, penetrates everything but hardest metals
Extensive use in medical imaging

18. Ultraviolet Radiation
Beneficial in small amounts, damaging in large
Absorbed by ozone layer

19. Visible Spectrum Humans eyes sensitive to this region
0.4 µm < λ < 0.7 µm
Humans eyes sensitive to this region
Majority of solar radiation in this region
widely used in remote sensing

20. Infrared Spectrum 0.7 µm < λ < 100 µm Two major subdivisions:
Reflective (also near and middle IR) – 0.7 µm < λ < 3.0 µm
Thermal (also emissive, radiative) -- 3 µm < λ < 100 µm
Very widely used in remote sensing

21. Microwave Radiation
1 mm – 1 m
Regions are indicated by a letter code: P, L, X, etc.
Widely used in remote sensing -- Radar

22. Particle Model of EMR (Quantum theory)
Energy is transferred in discrete packets called quanta or photons. The relationship between the frequency of radiation expressed by wave theory and the quantum is:
Q = h ν
where Q - energy of a quantum measured in
Joules (J),
h - Planck constant (6.626 x 10-34J s-1),
ν - frequency of the radiation.

23. Two Very Important Things about EMR:
Radiation Laws
Two Very Important Things about EMR:
EMR is emitted by any object with a temperature greater than absolute zero (i.e. > 0 Kelvin) (K = ˚C + 273)
The hotter the object, the more EMR it emits, at higher energy, and at shorter wavelengths.

24. Planck’s Blackbody Radiation Law
A blackbody is a hypothetical, ideal radiator that
totally absorbs and reemits all energy
incident upon it at a given temperature.
We may think of the Sun as a 6,000 ˚K blackbody.
Planck’s law gives the relationship between energy emitted,
temperature, and wavelength of blackbody.

25. Planck’s Law h = Planck’s constant
Planck's law describes the spectral radiance of electromagnetic radiation at all wavelengths emitted in the normal direction from a black body at temperature T.
h = Planck’s constant
k = Boltzmann constant (=1.38*10-23 JK-1)
c = speed of light (constant)
T = temperature (in K)
λ = Wavelength

26. Blackbody Radiation Curves Planck’s law solved for λ at constant T
Blackbody radiation curves for several objects including the Sun and the Earth which approximate 6,000 ˚K and 300 ˚K (27 ˚C) respectively.

27. Developments from Planck’s Law: Wien’s Displacement Law
Notice that the peak of the
Blackbody curve shifts to shorter wavelengths as
temperature increases.
This peak represents the wavelength of maximum emittance – dominant wavelength (λmax).

28. Wien’s Displacement Law
Note: Rλ(T) is the Planck
function
Solution:
This value is called Wien’s constant

29. Examples of Wien’s Law λmax of Earth (temperature = 300 K)
λmax = 2898 μm*K/300 K
λmax = 9.7 μm
λmax of Sun (temperature = 6000 K)
λmax = 2898 μm*K/6000 K
λmax = 0.48 μm