Truck Characteristics Analysis from All Aspect
Angles with Quad-pol Radarsat-2 Images
ZHANG Bo, WANG Chao, ZHANG Hong
July 26, IGRASS 2011
Outline
•
•
•
•
Motivation
Experiment data
Analysis method and discussion
Conclusion
Outline
•
•
•
•
Motivation
Experiment data
Analysis method and discussion
Conclusion
Motivation
Advantage of SAR imaging
• Under all weather conditions
• Independent of sun illumination
High resolution SAR sensor
• Cosmos-Skeymed, TerraSAR-X,Radarsat-2
Extended SAR application
• Traffic monitoring
Motivation
Related
traffic
monitoring
research
[1] Gintautas Palubinskas and Hartmut Runge. Rasar Signatures of a Passenger CAR. IEEE Geoscience and Remote Sensing Letters,
Vol.4,No.4,2007
[2] D. Hounam, S. Baumgartner, K. H. Bethke, M. etc. , “An autonomous, non-cooperative, wide-area traffic monitoring system using spacebased radar (TRAMRAD),” in Proc. IGARSS, Seoul, Korea, Jul. 2005, pp. 2917–2920.
Motivation
• Analysis of the influence of vehicle
motion and velocity
Related
traffic
monitorin
g
research
• Parking or moving Vehicle
characteristic
• Detector designing
• DPCA, ATI, FM, Integration detector
• Verification and performance analysis
Their researches are based on the air-born E-SAR data.
Outline
•
•
•
•
Motivation
Experiment data
Analysis method and discussion
Conclusion
Experiment data
Radarsat-2 quad polarimetric SAR images
Site
Center
frequency
(Hz)
Pixel space
(m) (RA)
Incidence
angle
Hainan
5.4E9
4.734.92
Jiangsu
5.4E9
Hubei
5.4E9
what size of the truck
can be detected?
Orbit
Range
bandwidth
(Hz)
Look
numbe
rs
22.16°24.09°
Ascending
3.0E7
11
4.734.74
38.37°39.84°
Descending
3.0E7
11
4.735.06
47.56°48.74°
Descending
3.0E7
11
How to change the characteristics
with aspect angle?
How do truck structure
affect characteristics?
（A）Medium truck （B）Carriage
（C）larger truck
（D）Tank truck
Experiment data
Incidence angle
Truck size
Aspect angle
Background
2009-2
23.2° 8.7，2.3，3.4
soil-rock
mixture
roadbed
23.2°
Time
5.7, 2.2, 2.6
2009-4
2009-9
39.7°
11.9, 2.5, 3.8
Asphalt road
2010-3
2010-6
48.1°
15.8, 2.5, 3.98
10.9, 2.47, 3.22
Concrete road
2010-10
Outline
•
•
•
•
Motivation
Experiment data
Analysis method and discussion
Conclusion
Analysis methods and discussion
Angles measurement
aspect angle: ∠S = A + ∆A+∆B
SAR Orbit
x
Z
A:
True north
ΔB
Incidence angle
ΔA
∆A:
local magnetic declination
∆B:
inverse calculated by the
four corners’ geographic
coordinates in SAR image
Magnetic north
θ
A
Truck heading
measured by compass
y
Incidence angle:
Calculated on the ellipsoid surface
SAR swath width
Analysis methods and discussion
Aspect angle
Intersection angle
0/0,225/45,270/90
As the left and right sides of truck
are symmetrical, the scope of
aspect angle can be reduced from
[0, 360] to [0, 180].
180/0,225/45,270/90
The front and rear shape of truck
are almost similar. To facilitate
comparison, the aspect angle can
181/1,193/13,206/26
be approximately replaced by the
217/37,223/43,229/49
minimum intersection angle which
239/59,251/71,262/82
is the angle between x-direction
,272/92
and long side of truck. So the
intersection angle is in the range
of [0, 90].
2/2,351/9,151/29,45/45
Analysis methods and discussion
Target and background RCS measurement

 
 
 
0
( x, y )dxdy  x y    0 (c, t )
c ,t
x  y
the area of one pixel in SAR image

stands for the area integral at the position of (c, t)
c ,t
 0  c, t 
k  [a, b, c, d ]

1
( Shh  Svv
2
Shh  Svv
Shv  Svh i(Svh  Shvvh ))
SPAN = Shh
2
+ Shv
2
+ Svh
2
+ Svv
2
Discussion of SPAN value
A
B
C
Four types truck SPAN value characteristic pattern with
intersection angle and incidence angle.
Truck size :
A<C<D
which factor is more impacted
on RCS value within incidence
angle and size?
SPAN value:
D<A<C
structure is the key factor
Incidence angle:
D
A<C<D
Discussion of background value
Four types truck SPAN value characteristic
For the wavelength of Raradarsat-2 beam is 5.5 cm and roads are relatively smooth, the
clutter of background shows lower at larger incidence angle, which will improve truck
detection ratio. Considering the impact of incidence angle on the translation of slant range to
ground range, it can be concluded that same truck will occupy more pixels on slant range
and bring stronger backscatter on larger incidence angle image. In short, the larger incidence
angle SAR image will be more favorable to truck detection.
Discussion of the impact aspect angle
the even bounce is always bigger than other Pauli components except at the
intersection angle around 45°.
the higher SPAN value between 43° and 71° is due to the odd bounce which may
be caused by the rough truck tarpaulin roof.
The smooth and bare cylindrical structure of tank truck lead to the odd backscatter
bounce very weak.
Conclusion
 Structure rather than size is the key factor
which affects the truck characteristics.
Structure
 When the truck heading turning form
perpendicular to parallel to the SAR
illumination, the even bounce intensity will
be decreased at first and then increased,
the alter angle is 45°.
RCS
Incidence
angle
Aspect
angle
 Incidence angle also impact the RCS
value. But its impact on the background
will be even greater . it can be confident
that SAR image at larger incidence angle
is beneficial to increase the detection ratio
for truck detection.