Basic Definitions And Laws

1
FUNDAMENTALS
CHAPTER 2
Basic Definitions And Laws Of Electromagnetic
Radiation
A. Dermanis
2
Sensors collect electromagnetic energy ?Q
emitted from a surface area ?? (pixel), during
a time interval ?t, arriving at the sensor
aperture with a solid angle ?O
?O
P
??
A. Dermanis
3
Sensors collect electromagnetic energy ?Q
emitted from a surface area ?? (pixel), during
a time interval ?t, arriving at the sensor
aperture with a solid angle ?O
?O
?? characterize the intensity of
electromagnetic radiation we must get rid of ??,
?t and ?O !
P
??
A. Dermanis
4
Sensors collect electromagnetic energy ?Q
emitted from a surface area ?? (pixel), during
a time interval ?t, arriving at the sensor
aperture with a solid angle ?O
?O
?? characterize the intensity of
electromagnetic radiation we must get rid of ??,
?t and ?O !
P
??
Basic definitions (Q energy)
A. Dermanis
5
Sensors collect electromagnetic energy ?Q
emitted from a surface area ?? (pixel), during
a time interval ?t, arriving at the sensor
aperture with a solid angle ?O
?O
?? characterize the intensity of
electromagnetic radiation we must get rid of ??,
?t and ?O !
P
??
Basic definitions (Q energy)
radiant flux F(t)
(power !)
A. Dermanis
6
Sensors collect electromagnetic energy ?Q
emitted from a surface area ?? (pixel), during
a time interval ?t, arriving at the sensor
aperture with a solid angle ?O
?O
?? characterize the intensity of
electromagnetic radiation we must get rid of ??,
?t and ?O !
P
??
Basic definitions (Q energy)
radiant flux F(t)
(power !)
radiant exitance M(t,P)
(emitted)
A. Dermanis
7
Sensors collect electromagnetic energy ?Q
emitted from a surface area ?? (pixel), during
a time interval ?t, arriving at the sensor
aperture with a solid angle ?O
?O
?? characterize the intensity of
electromagnetic radiation we must get rid of ??,
?t and ?O !
P
??
Basic definitions (Q energy)
radiant flux F(t)
(power !)
radiant exitance M(t,P)
(emitted)
irradiance E(t,P)
(incident)
A. Dermanis
8
Sensors collect electromagnetic energy ?Q
emitted from a surface area ?? (pixel), during
a time interval ?t, arriving at the sensor
aperture with a solid angle ?O
?O
?? characterize the intensity of
electromagnetic radiation we must get rid of ??,
?t and ?O !
P
??
Basic definitions (Q energy)
radiant flux F(t)
(power !)
radiant exitance M(t,P)
(emitted)
irradiance E(t,P)
(incident)
illuminance L
(p half upper space)
A. Dermanis
9
Electromagnetic signals x(t) consist of sines and
cosines
with varying periods T, or angular frequencies
? 2p/?, or wavelengths ? cT (c light
velocity)
A. Dermanis
10
Electromagnetic signals x(t) consist of sines and
cosines
with varying periods T, or angular frequencies
? 2p/?, or wavelengths ? cT (c light
velocity)
Fourier analysis
A. Dermanis
11
signal power
S (?) power spectral density function
A. Dermanis
12
signal power
S (?) power spectral density function
radiant flux (power)
exitance (with ??? cT 2pc/?)
A. Dermanis
13
signal power
S (?) power spectral density function
radiant flux (power)
exitance (with ??? cT 2pc/?)
spectral exitance
A. Dermanis
14
Sensors respond to exitance only within a
spectral band ?1 ? ? ? ?2
Ideal sensor
A. Dermanis
15
Sensors respond to exitance only within a
spectral band ?1 ? ? ? ?2
Ideal sensor
Actual sensor
w(?) sensor sensitivity response function
A. Dermanis
16
Sensors respond to exitance only within a
spectral band ?1 ? ? ? ?2
Ideal sensor
Actual sensor
w(?) sensor sensitivity response function
response functions for the 4 sensors of the
Landsat satellite Multispectral Scanner
A. Dermanis
17
The Electromgnetic Spectrum
?
cm
A
102
102
0.1
1
10
103
104
105
106
0.1
1
10
103
104
105
106
107
µ
m
km
A
cm
300
30
3
300
30
3
30
3
300
30
3
30
3
0.3
0.3
0.2
300
0.3
RADAR
?
RADIO
AUDIO
AC
?
MICROWAVES
IR
UV
VISIBLE
Red ? IR (Infrared)
UV (Ultraviolet) ? Violet
A. Dermanis
18
Spectral Bands of Landsat Satellite - Thematic
Mapper (T1, T2, T3, T4, T5) and SPOT4 Satellite
HRVIR (S1, S2, S3, S4)
1. water 2. vegetation 3. bare soil 4. snow
A. Dermanis
19
Laws of Electromgnetic Radiation
black body an idealized body absorbing all
wavelengths of incident radiation or emitting
radiation at all wavelengths Physical
approximation sun! T temperature
A. Dermanis
20
Laws of Electromgnetic Radiation
black body an idealized body absorbing all
wavelengths of incident radiation or emitting
radiation at all wavelengths Physical
approximation sun! T temperature
Law of Plank (spectral exitance of black body)
A. Dermanis
21
Laws of Electromgnetic Radiation
black body an idealized body absorbing all
wavelengths of incident radiation or emitting
radiation at all wavelengths Physical
approximation sun! T temperature
Law of Plank (spectral exitance of black body)
Law of Stefan-Bolzman (total spectral exitance)
A. Dermanis
22
Laws of Electromgnetic Radiation
black body an idealized body absorbing all
wavelengths of incident radiation or emitting
radiation at all wavelengths Physical
approximation sun! T temperature
Law of Plank (spectral exitance of black body)
Law of Stefan-Bolzman (total spectral exitance)
Law of Wien (? of maximal spectral exitance)
A. Dermanis
23
The Solar Electromgnetic Radiation
solar irradiance below atmosphere
atmospheric absorption
A. Dermanis