Radar Part 1

Question 1

RADAR is a method for…

Answer 1

Detecting the position AND velocity of a distant object using active energy source

Question 2

Radar is a…

Answer 2

Side looking imaging system

Question 3

In contrast to optical remote sensing systems…

Answer 3

All weather and 24 hour illumination

Question 4

What does it mean if Radar radiation is pure?

Answer 4

Radiation is at a single wavelength and frequency, unlike the sun which consists of energies at various wavelengths

SAR transmits its microwave at a designed and fixed wavelength

Question 5

What are the 3 primary functions of a radar system?

Answer 5

Transmits microwave signals
Recieves the backscattered signals
Records the strength and time delay (phase) of return signals

Measure amplitude of return signal and face angle (sensor-ground-sensor) which is 0-360d.

Question 6

What is a phase value?

Answer 6

Distance the wave has travelled

Question 7

What does in and out of phase mean?

Answer 7

In phase means two waves pass the same point at the same time
Out of phase means trough of one and crest of other pass at the same time (maximum out by 180 degrees)

Question 8

Radar shows the difference in…

Answer 8

Surface roughness
Geometry
Moisture Content on the Ground

Question 9

What are the 5 types of surface scattering?

Answer 9

Smooth specular
Intermediate specular & diffuse
Rough diffuse
Specular and double bounce
Volume scattering

Question 10

What is volume scattering?

Answer 10

Scattering of radar energy within a volume (tree canopy) with multiple bounces from different components (branch, leaves, animals) within the volume

Question 11

How is surface roughness quanitifed?

Answer 11

By the vertical deviation of a real surface from its ideal form

LARGE = ROUGH
SMALL = SMOOTH

Question 12

How can surface roughness be measured?

Answer 12

Surface is roughness or smoothness is a relative comparison to the wavelength

Question 13

How do you formula the boundary between specular and diffuse reflection

Answer 13

H (boundary surface roughness) = Y (wavelength of incident wave) / 0 (incident angle)

Question 14

What is the notation for boundary condition surface roughness AND
actual surface roughness

Explain the relationship betwen the two notations

Answer 14

HB
HS

HS < HB = specular manner surface
HS > HB diffuse manner surface
HS = HB reflection intermediate between diffuse and specular

Question 15

What is RPD (Radar Penetration Depth)

Answer 15

Penetration depth (through physical objects) will increase with increasing wavelength (such as into soil, or forests)

Question 15

Biggest rule of SAR!!

Answer 15

SAR can see objects the same size as its wavelength or larger!

Question 16

Are most objects considered rough or smooth?

Answer 16

Rough, but it can be changed by the face angle such as a mirroring still lake