The document introduces radar remote sensing, outlining its components and the differences between passive and active remote sensing. It highlights the advantages of radar, including its ability to penetrate cloud cover, operate at night, and provide insights into surface properties. Additionally, it discusses various factors affecting radar signal and backscatter, including surface characteristics and polarization types.

1. Ali Ghadiri
2024_11
Introduction to Radar

2. Passive / Active Remote Sensing
Brief History of RADAR Remote Sensing
RADAR System Components
RADAR/Surface Interactions
LIDAR

3. Passive / Active Remote Sensing
 Passive” remote sensors detect reflected (e.g.,
visible, NIR) or emitted (e.g., TIR) EMR off the Earth’s
surface
 Active” remote sensors are dependent upon neither
EMR from the Sun nor thermal emission from Earth
surfaces. They create and transmit EMR and record
the return.

5. Radar's advantages in environmental RS
 Active microwave energy penetrates cloud cover
(all-weather systems);
 Can be obtained at user-specified times (even at night);
 Senses in wavelengths outside the visible and infrared parts of the
spectrum … provides additional information on Earth surfaces (e.g.,
surface roughness and moisture content, dielectric properties).
 multi-frequency potential , different types of polarized energy
 Provides its own source of illumination, which can be controlled; and
Permits measurements of ocean and lake wave properties.
 overlapping images suitable for stereoscopic viewing and radar grammetry.

6. Backscatter

7. Backscatter

8. The electromagnetic spectrum (the
Microwaves spectrum highlighted)
12 10 9 8 7 6 5 4 3 2
13 11
10 10 10 10 10 10 10 10 10 10 10 10
10
14
0.01 0.1 1 10 100 1 1
10 10
100 10
0.1 0.1 1
0.4 0.5 0.6 0.7 µm
VISIBLE SPECTRUM
X RAYS
GAMMA
RAYS
Wavelength ()
Frequency (MHz)
Angstroms Micrometers Centimetres Meters
UHF VHF
MICROWAVES
BLUE GREEN RED
RADAR
MIDDLE
NEAR
ULTRA-VIOLET
THERMAL
RADIO, TV.
INFRARED

9. Microwaves standards domain
Radar remote sensing

11. 1 2 3 4 5 6 7 8 9
100
60
40
20
0
80
Ice clouds
Water clouds
X L Bands
C
Atmospheric
transmissivity
Cloud transmisivity in the
microwave region
(adapted from ESA, 1995)

12. Micro-wave versus optical observation
Right: JERS-1 red
reflectance.
Left: JERS-1
RADAR image of
the same area.
Images acquired
simultaneously.
Manaos, 1993.
Source: NASDA.

13. Name Width (cm) Central value Frequency (GHz)
Ka 0.75 1.10
K 1.10 1.67 1.0 10.9 36
Ku 1.67 2.40
X 2.40 3.75 3.0 5.75 10.90
C 3.75 7.50 5.6 3.90 5.75
S 7.50 15.00 10.0 1.55 3.90
L 15.00 30.00 23.0 0.39 1.55
P 30.00 100.00 70.0 > 0.39
Bands frequently used in micro-
wave remote sensing

14. Factors in the RADAR signal
 Surface properties:
 Dialectric constant.
 Roughness.
 Observation characteristics:
 Wavelenght.
 Incidence angle.
 Polarization.

15. Difuse backscatter
Corner backscattering
Specular backscatter
Different backscatter types
(adapted from Campbell, 1996)

16. h = 0,72 a 1,32 cm
 = 5,65 cm
Depression angle
 = 77°
S
p
e
c
u
l
a
r
b
a
c
k
s
c
a
t
t
e
r
h < 0,72 cm
h > 1,32 cm
(i)
(ii)
(iii)
(i) smooth surface, low
backscatter; (ii)
moderately rouge
surface, medium
backscatter; (iii) rough
surface, high backscatter
(adapted from Lillesand
and Kiefer, 2000).
Backscatter variations as a result
of roughness and wavelength

17. Cortesy DAIS (Buenos Aires Province, Argentina)
Oil spills in the coast of Argentina (near
Mar del Plata), as seen by Radarsat images

18. VH
HH
HV
VV
Polarization types
H Horizontal
V Vertical

19. (after NASA, 1987)
Penetration of microwave signals
in vegetation, soils and ice