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Extraction and Analysis of Polarimetric Interferometry Information of SAR Targets
Available online at www.sciencedirect.com Available online at www.sciencedirect.com
Procedia Engineering
Procedia Engineering 00 (2011) 000–000 Procedia Engineering 15 (2011) 2057 – 2061 www.elsevier.com/locate/procedia
Advanced in Control Engineeringand Information Science
Extraction and Analysis of Polarimetric Interferometry Information of SAR Targets Huang Shiqi ∗ a, Liu Zhiganga, , Zhang Qingmina ,Yuan Yia a
Xi’an Research Institute of Hi-Tech, Hongqing Town, 710025, Xi’an, P. R. China
Abstract The polarimetric interferometry synthetic aperture radar (SAR) imaging not only can obtain spacial information of a target, but also can obtain height information of a target. Therefore, it is applied widely, and it is also a focus of remote sensing field. This paper combines the mechanism of a target scattering and the theory of polarimetric interferometry, and some correlated information is extracted, which is explained by physics meaning. Polarimetric SAR; Interferometry SAR; information extraction, physical meanting
© 2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of [CEIS 2011] Keywords: Polarimetric SAR; Interferometry SAR; information extraction, physical meanting
1. Introduction The traditional SAR only uses the energy of the electromagnetic wave scattering echo to perform imaging under the transmitting and receiving antenna of special polarization. However, the polarimetric information is the scattering characteristics which the ground objects aim at the different polarimetric electromagnetic wave, and it supplies more exact information for target recognition and classification. The polarimetric SAR (Pol-SAR) uses the different polarization channels obtain complex images to distinguish the physical parameters, such as objective small structures, objective directions, objective proportions and physical composition, and extracts the ground object information [1-4].
∗
Corresponding author. Tel.:+8615349226380
E-mail address:[email protected]
1877-7058 © 2011 Published by Elsevier Ltd. doi:10.1016/j.proeng.2011.08.384
2058 2
Huang Shiqialet/ al. / Procedia Engineering 15 (2011) 2057 – 2061 Huang S Q,et Procedia Engineering 00 (2011) 000–000
The interferometry SAR (In-SAR) can supply the vertical structure information of remote sensing objects and reflect the physical parameters of the ground object scattering mechanism. The basic theory of In-SAR is using two complex SAR images of the same area and different incidence angles to found the polarimetric interferometry spectrum, and on the basic of it, to extract the remote sensing object information. Because of the nonuniformity of the geometrical features, for example, the ground inclination and the roughness, the affection of the terrene vegetation and the volume scattering, the process of electromagnetic wave scattering is greatly complex. There are a lot of scattering mechanism in a resolution cell, and the uncertainty of the phase center of all kinds of scattering mechanism affects the precision of the interferometry measurement. These reasons limit the applications of In-SAR [5-6]. The polarimetric interferometry SAR (Pol-In-SAR) is a new technique of the Earth observation which has been developed in recent years, combining the advantages of Plo-SAR and In-SAR. Therefore, PolIn-SAR has the characteristics of being sensitive to not only the spacial distribution and the height, but also the configuration and direction. At present, the full Pol-In-SAR is the radar which can obtain the most abundant remote sensing data. This is the advantage that the general SAR cannot reach, and it is quite in favor of improve the ability of sesoving the practial application problems. This paper discusses the imaging mechanism of Pol-In-SAR and the polarimetric interferometry information extracting, and explains them from the physical mechanism. 2. The imaging mechanism and physical meaning of Pol-In-SAR A random symmetry scattering matrix can be defined by the Equation (1).
⎡a b ⎤ [S ] = ⎢ ⎥ ⎣b c ⎦
(1)
r The scattering vector k of the corresponding Pauli matrix can be simplified as follow.
r 1 r r T k= [ a + c a − c 2b] = k ω 2
(2)
r Where ω is a normalized complex vector, and it denotes the scattering mechanism, and the expression is
⎡ cos α exp(iφ ) ⎤ ω = ⎢⎢sin α cos β exp(iδ ) ⎥⎥ ⎢⎣ sin α sin β exp(iγ ) ⎥⎦ r
(3)
It drawns out a greatly important simplifying criteria of the scattering vector, that is a random r scattering mechanism which abides by reciprocity and is discripted by the complex vector ω can be simplified in to [1 0 0]T through the next series of matrix thrnsform.
⎡1 ⎤ ⎡ cos α ⎢ ⎥ ⎢ ⎢ 0 ⎥ = ⎢ − sin α ⎢⎣0 ⎥⎦ ⎢⎣ 0
sin α cos α 0
0 ⎤ ⎡1 0 ⎥ ⎢ 0 ⎥ ⎢0 cos β 1 ⎥⎦ ⎢⎣0 − sin β
0 ⎤ ⎡ exp( −iφ ) 0 0 ⎤ ⎥ ⎢ ⎥ sin β ⎥ ⎢ 0 exp(−iδ ) 0 ⎥ω cos β ⎥⎦ ⎢⎣ 0 0 exp( −iγ ) ⎥⎦
(4)
In Equation (4), the third matrix denotes a set of scattering phase angle at right. For the first matrix and the second matrix, if it is thought from the mathematical view, they are a sort of specification expression of the revolution of plane, if it is thought from the physical view, only does β denotes the physical revolution that the scatterer relatives to the direction of the radar line sight. What α stand for is the freedom degrees within scatterers, which denotes the type of the scattering mechanism, and the range of its value is 0o ≤ α ≤ 90o . When α = 0o , it denotes the surface reflection of the isotropism; when
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et al. / Q Procedia (2011) 205700– (2011) 2061 000–000 Huang SHuang Q, Liu Shiqi Z G, Zhang M, YuanEngineering Y / Procedia15Engineering
α = 90o , it denotes the dihedral reflection of the isotropism, when α = 90o ; when α is other values , it denotes the scattering mechanism of the anisotropism, here, HH is unequal to VV ; when α = 45o , it is corresponding to the dipole scattering, here, there is a co-polarization scattering coefficient and the value is zero. r r For full polarimetric interferometry, if ω 1 and ω 2 denote two special scattering mechanisms, and the r r r r r r r r projections of k1 and k2 on ω 1 and ω 2 are μ 1 and μ 2 , respectively, μ 1 and μ 2 denote the scattering components that are corresponding to two special scattering mechanisms. They are defined by
r r ⎧⎪ μ1 = ω *1T k 1 ⎨ r *T r ⎪⎩ μ2 = ω 2 k 2
(5)
r r The scalar functions μ 1 and μ 2 denote the linear combination of the element of the scattering matrix [ S1 ] and [ S2 ] , respectively, and they are the basic of forming the vector interferometric image. Here, the coherent matrix [ J ] is defined by
r r r r ⎡ ω *1T [T11 ]ω 1 ω *1T [Ω12 ]ω 2 ⎤ μ ⎤⎦ = ⎢ r *T r *T r ⎥ *T r ⎣ω 2 [Ω12 ] ω 1 ω 2 [T22 ]ω 2 ⎦
⎡μ ⎤ [ J ] = ⎢ 1 ⎥ ⎡⎣ μ1* ⎣ μ2 ⎦
* 2
(6)
The definition of interferometric image can be obtained by Equation (5) and Equation (6) and it is defined by
(
r r
)(
r r
μ1μ2* = ω *1T k1 ω *2T k2
)
*T
r r = ω *1T [Ω12 ]ω 2
(7)
From Equation (7), the expression of the interferometric phase can be given by
(r
r r r
)
φi = arg ω *1T k1 k *2T ω 2 = arg (ω *1T [Ω12 ]ω 2 ) r
r
(8)
And the vector expression of polarimetric interferometry coefficients is given by
γ=
μ1μ2* μ1μ1* μ2 μ2*
=
J12 J11 J 22
r
=
r
ω *1T [Ω12 ]ω 2 r
r
r
r
ω *1T [T11 ]ω 1 ω *2T [T22 ]ω 2
(9)
3. Extraction of polarimetric interferometry information The polarimetric interferometry SAR measurement technique is developed on basic of the Pol-SAR and In-SAR techniques, and it is also the production that the interferential measurement algorthim is applied the polarimetric SAR. Therefore, the Pol-In-SAR measurement algorithm is on the basic of interferential algorithm, and then combines the processing methods of polarimetric information. The PolIn-SAR algorithm includes the next main parts, such as the SAR image pre-processing operations, the image registration operations, the produced phase image, the removing flat effect, the phase unwrapping, the digital elevation model (EMD) extracting, and the fig.1 shows the flow chart of the polarimetric interferometry SAR processing.
Fig.1 The flow chart of the Pol-In-SAR processing
2060 4
Huang Shiqialet/ al. / Procedia Engineering 15 (2011) 2057 – 2061 Huang S Q,et Procedia Engineering 00 (2011) 000–000
4. Experimental results and analysis 4.1 The experiment of extracting interferometric information of SAR targets The experimental data comes from SIR-C/X-SAR imaging system, and the imaging area is Etna volcano in Italy, and the time is 1994. The flight track height H is 220 km, the baseline B is 60 m, the radar frequency f 0 is 9.602 GHz, the wavelength λ is 0. 03122285m. The experimental data is near the volcano entrance, and the size of the image is 1024 × 1024 , which is shown in Fig.2. Where Fig.2(a) is the single look complex image of the master image, and Fig.2(b) is the single look complex image of the track image.
(a) (b) Fig.2 The master and track images
What Fig.3 shows is the DEM which is obtained by the single polarization. Fig.3(a) is the interferometric stripe image of Fig.2, Fig.3(b) is the DEM, Fig.3(c) is the three dimension shape of DEM. In Fig.3(b), it uses a window to smooth noise and the size of it is 3 × 3 .
azim uth
e rang
(a) (b) (c) Fig.3 The DEM obtained by single polarization SAR images
4.2 The experiment of extracting polarimetric interferometry information of SAR targets The simulation data is produced by the Polsarpro4.0. The simulative area is a flat ground, and there are seventeen deciduous trees at the center of the area. The vegetated area model is shown in Fig.4 and the simulative parameters are show in Table 1. Although the ground is flat, there are some roughness.
Fig.4 The simulative data model Table 1 The parameters of producing full polarimetric interferometry imaging data Type Value Type Value platform centre frequency
f 0 = 1.3 GHz
incidence angle
tree height
horizontal baseline
azimuth resolution
h = 18 m ρ a = 1.5 m
range resolution
ρ r = 1.06
platform height
H = 3000 m
vertical baseline
Bv = 1 m
θ = 300
Bh = 10 m
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et al. / Q Procedia (2011) 205700– (2011) 2061 000–000 Huang SHuang Q, Liu Shiqi Z G, Zhang M, YuanEngineering Y / Procedia15Engineering
The polarimetric information and the scattering information of every antenna can be analysized through the polarimetric interferometry scattering matrix T6 , and it includes the amplitude and phase information of all channels. In experiments, assume that HV = VH , that is the symmetric target and they can exchange with each other. The definition of T6 is given by ⎡ T 11 ⎢T 21 ⎢ ⎢T 31 T6 = ⎢ ⎢T 41 ⎢T 51 ⎢ ⎣⎢T 61
T 12 T 13 T 14 T 15 T 16 ⎤ T 22 T 23 T 24 T 25 T 26 ⎥⎥ T 32 T 33 T 34 T 35 T 36 ⎥ ⎡ T11 ⎥=⎢ H T 42 T 43 T 44 T 45 T 46 ⎥ ⎢⎣Ω12 T 52 T 53 T 54 T 55 T 56 ⎥ ⎥ T 62 T 63 T 64 T 65 T 66 ⎦⎥
Ω12 ⎤ ⎥ T22 ⎥⎦
(10)
Through the analysis of the mentioned full polarimetric interferometry SAR imaging mechanism, choosing different polarimetric scattering mechanism ω1 and ω2 , six different polarimetric interferometry models can be obtained, i.e. HH interferometry, HV interferometry, VV interferometry, HH-VV interferometry, HH+VV interferometry and HV+VH interferometry. The phase center elevation estimations of six different polarimetric interferometry methods are shown in Fig.5. It can be seen from Fig.5 that the different polarimetric combination can obtain different polarimetric information and it is great in favor of improving the interferometric precision.
(a) HH (b) HV (c) VV (d) HH+VV (e) HH-VV (f) HV+VH Fig.5 The estimated results of the elevation information of different polarimetric interferometry center phase
5. Conclusions
The polarimetric interferometry SAR is one of the great important field which modern radars develop, it not only can supply abundant targtet information, but also obtain the DEM of a target, therefore, the applications is more and more wider. This paper mainly discusses the imaging mechanism of Pol-In-SAR and extracting the polarimetric interferometry information, what’s more, these information is explained from the scattering mechanism. References [1] Nord M E, et al.. Comparison of compact polarimetric synthetic aperture radar modes. IEEE Transactions on Geoscience and Remote Sensing, 2009, 47(1): 174-188. [2] Cloude S R and Pnpnthnnnssiou K P. Three-stage process for polnrimetric SAR
interferometriy. IEE Proceeding of
Radar Sonar Navigation, 2003, 150(3): 125-134. [3] Tan L L, Yank L B, Yang R L. Investigation on vegetation height retrieval technique with compact PolInSAR data. Journal of Electronics & Information Technology (In China), 2010, 32(12): 2814-2819. [4] Luo H M, Chen E X, Cheng J, Li X W. Forest height estimation methods using polarimetric SAR interferometry. Journal of Remote Sensing (In China), 2010, 14(4): 806-821. [5] Zhou M, Wang X H, Tang L L, Li C R. Developments and applications of polarimetric SAR interferometry techniques. Science and Technology Guide Report (In China), 2008, 26(21): 90-93. [6] Zou B, Zhang L M, Sun D M, Wang W. Information extraction using polarimetric interferometric SAR Data: Present and Future.. Journal of Electronics & Information Technology (In China), 2006, 28(10): 1979-1984.
Procedia Engineering
Procedia Engineering 00 (2011) 000–000 Procedia Engineering 15 (2011) 2057 – 2061 www.elsevier.com/locate/procedia
Advanced in Control Engineeringand Information Science
Extraction and Analysis of Polarimetric Interferometry Information of SAR Targets Huang Shiqi ∗ a, Liu Zhiganga, , Zhang Qingmina ,Yuan Yia a
Xi’an Research Institute of Hi-Tech, Hongqing Town, 710025, Xi’an, P. R. China
Abstract The polarimetric interferometry synthetic aperture radar (SAR) imaging not only can obtain spacial information of a target, but also can obtain height information of a target. Therefore, it is applied widely, and it is also a focus of remote sensing field. This paper combines the mechanism of a target scattering and the theory of polarimetric interferometry, and some correlated information is extracted, which is explained by physics meaning. Polarimetric SAR; Interferometry SAR; information extraction, physical meanting
© 2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of [CEIS 2011] Keywords: Polarimetric SAR; Interferometry SAR; information extraction, physical meanting
1. Introduction The traditional SAR only uses the energy of the electromagnetic wave scattering echo to perform imaging under the transmitting and receiving antenna of special polarization. However, the polarimetric information is the scattering characteristics which the ground objects aim at the different polarimetric electromagnetic wave, and it supplies more exact information for target recognition and classification. The polarimetric SAR (Pol-SAR) uses the different polarization channels obtain complex images to distinguish the physical parameters, such as objective small structures, objective directions, objective proportions and physical composition, and extracts the ground object information [1-4].
∗
Corresponding author. Tel.:+8615349226380
E-mail address:[email protected]
1877-7058 © 2011 Published by Elsevier Ltd. doi:10.1016/j.proeng.2011.08.384
2058 2
Huang Shiqialet/ al. / Procedia Engineering 15 (2011) 2057 – 2061 Huang S Q,et Procedia Engineering 00 (2011) 000–000
The interferometry SAR (In-SAR) can supply the vertical structure information of remote sensing objects and reflect the physical parameters of the ground object scattering mechanism. The basic theory of In-SAR is using two complex SAR images of the same area and different incidence angles to found the polarimetric interferometry spectrum, and on the basic of it, to extract the remote sensing object information. Because of the nonuniformity of the geometrical features, for example, the ground inclination and the roughness, the affection of the terrene vegetation and the volume scattering, the process of electromagnetic wave scattering is greatly complex. There are a lot of scattering mechanism in a resolution cell, and the uncertainty of the phase center of all kinds of scattering mechanism affects the precision of the interferometry measurement. These reasons limit the applications of In-SAR [5-6]. The polarimetric interferometry SAR (Pol-In-SAR) is a new technique of the Earth observation which has been developed in recent years, combining the advantages of Plo-SAR and In-SAR. Therefore, PolIn-SAR has the characteristics of being sensitive to not only the spacial distribution and the height, but also the configuration and direction. At present, the full Pol-In-SAR is the radar which can obtain the most abundant remote sensing data. This is the advantage that the general SAR cannot reach, and it is quite in favor of improve the ability of sesoving the practial application problems. This paper discusses the imaging mechanism of Pol-In-SAR and the polarimetric interferometry information extracting, and explains them from the physical mechanism. 2. The imaging mechanism and physical meaning of Pol-In-SAR A random symmetry scattering matrix can be defined by the Equation (1).
⎡a b ⎤ [S ] = ⎢ ⎥ ⎣b c ⎦
(1)
r The scattering vector k of the corresponding Pauli matrix can be simplified as follow.
r 1 r r T k= [ a + c a − c 2b] = k ω 2
(2)
r Where ω is a normalized complex vector, and it denotes the scattering mechanism, and the expression is
⎡ cos α exp(iφ ) ⎤ ω = ⎢⎢sin α cos β exp(iδ ) ⎥⎥ ⎢⎣ sin α sin β exp(iγ ) ⎥⎦ r
(3)
It drawns out a greatly important simplifying criteria of the scattering vector, that is a random r scattering mechanism which abides by reciprocity and is discripted by the complex vector ω can be simplified in to [1 0 0]T through the next series of matrix thrnsform.
⎡1 ⎤ ⎡ cos α ⎢ ⎥ ⎢ ⎢ 0 ⎥ = ⎢ − sin α ⎢⎣0 ⎥⎦ ⎢⎣ 0
sin α cos α 0
0 ⎤ ⎡1 0 ⎥ ⎢ 0 ⎥ ⎢0 cos β 1 ⎥⎦ ⎢⎣0 − sin β
0 ⎤ ⎡ exp( −iφ ) 0 0 ⎤ ⎥ ⎢ ⎥ sin β ⎥ ⎢ 0 exp(−iδ ) 0 ⎥ω cos β ⎥⎦ ⎢⎣ 0 0 exp( −iγ ) ⎥⎦
(4)
In Equation (4), the third matrix denotes a set of scattering phase angle at right. For the first matrix and the second matrix, if it is thought from the mathematical view, they are a sort of specification expression of the revolution of plane, if it is thought from the physical view, only does β denotes the physical revolution that the scatterer relatives to the direction of the radar line sight. What α stand for is the freedom degrees within scatterers, which denotes the type of the scattering mechanism, and the range of its value is 0o ≤ α ≤ 90o . When α = 0o , it denotes the surface reflection of the isotropism; when
2059 3
et al. / Q Procedia (2011) 205700– (2011) 2061 000–000 Huang SHuang Q, Liu Shiqi Z G, Zhang M, YuanEngineering Y / Procedia15Engineering
α = 90o , it denotes the dihedral reflection of the isotropism, when α = 90o ; when α is other values , it denotes the scattering mechanism of the anisotropism, here, HH is unequal to VV ; when α = 45o , it is corresponding to the dipole scattering, here, there is a co-polarization scattering coefficient and the value is zero. r r For full polarimetric interferometry, if ω 1 and ω 2 denote two special scattering mechanisms, and the r r r r r r r r projections of k1 and k2 on ω 1 and ω 2 are μ 1 and μ 2 , respectively, μ 1 and μ 2 denote the scattering components that are corresponding to two special scattering mechanisms. They are defined by
r r ⎧⎪ μ1 = ω *1T k 1 ⎨ r *T r ⎪⎩ μ2 = ω 2 k 2
(5)
r r The scalar functions μ 1 and μ 2 denote the linear combination of the element of the scattering matrix [ S1 ] and [ S2 ] , respectively, and they are the basic of forming the vector interferometric image. Here, the coherent matrix [ J ] is defined by
r r r r ⎡ ω *1T [T11 ]ω 1 ω *1T [Ω12 ]ω 2 ⎤ μ ⎤⎦ = ⎢ r *T r *T r ⎥ *T r ⎣ω 2 [Ω12 ] ω 1 ω 2 [T22 ]ω 2 ⎦
⎡μ ⎤ [ J ] = ⎢ 1 ⎥ ⎡⎣ μ1* ⎣ μ2 ⎦
* 2
(6)
The definition of interferometric image can be obtained by Equation (5) and Equation (6) and it is defined by
(
r r
)(
r r
μ1μ2* = ω *1T k1 ω *2T k2
)
*T
r r = ω *1T [Ω12 ]ω 2
(7)
From Equation (7), the expression of the interferometric phase can be given by
(r
r r r
)
φi = arg ω *1T k1 k *2T ω 2 = arg (ω *1T [Ω12 ]ω 2 ) r
r
(8)
And the vector expression of polarimetric interferometry coefficients is given by
γ=
μ1μ2* μ1μ1* μ2 μ2*
=
J12 J11 J 22
r
=
r
ω *1T [Ω12 ]ω 2 r
r
r
r
ω *1T [T11 ]ω 1 ω *2T [T22 ]ω 2
(9)
3. Extraction of polarimetric interferometry information The polarimetric interferometry SAR measurement technique is developed on basic of the Pol-SAR and In-SAR techniques, and it is also the production that the interferential measurement algorthim is applied the polarimetric SAR. Therefore, the Pol-In-SAR measurement algorithm is on the basic of interferential algorithm, and then combines the processing methods of polarimetric information. The PolIn-SAR algorithm includes the next main parts, such as the SAR image pre-processing operations, the image registration operations, the produced phase image, the removing flat effect, the phase unwrapping, the digital elevation model (EMD) extracting, and the fig.1 shows the flow chart of the polarimetric interferometry SAR processing.
Fig.1 The flow chart of the Pol-In-SAR processing
2060 4
Huang Shiqialet/ al. / Procedia Engineering 15 (2011) 2057 – 2061 Huang S Q,et Procedia Engineering 00 (2011) 000–000
4. Experimental results and analysis 4.1 The experiment of extracting interferometric information of SAR targets The experimental data comes from SIR-C/X-SAR imaging system, and the imaging area is Etna volcano in Italy, and the time is 1994. The flight track height H is 220 km, the baseline B is 60 m, the radar frequency f 0 is 9.602 GHz, the wavelength λ is 0. 03122285m. The experimental data is near the volcano entrance, and the size of the image is 1024 × 1024 , which is shown in Fig.2. Where Fig.2(a) is the single look complex image of the master image, and Fig.2(b) is the single look complex image of the track image.
(a) (b) Fig.2 The master and track images
What Fig.3 shows is the DEM which is obtained by the single polarization. Fig.3(a) is the interferometric stripe image of Fig.2, Fig.3(b) is the DEM, Fig.3(c) is the three dimension shape of DEM. In Fig.3(b), it uses a window to smooth noise and the size of it is 3 × 3 .
azim uth
e rang
(a) (b) (c) Fig.3 The DEM obtained by single polarization SAR images
4.2 The experiment of extracting polarimetric interferometry information of SAR targets The simulation data is produced by the Polsarpro4.0. The simulative area is a flat ground, and there are seventeen deciduous trees at the center of the area. The vegetated area model is shown in Fig.4 and the simulative parameters are show in Table 1. Although the ground is flat, there are some roughness.
Fig.4 The simulative data model Table 1 The parameters of producing full polarimetric interferometry imaging data Type Value Type Value platform centre frequency
f 0 = 1.3 GHz
incidence angle
tree height
horizontal baseline
azimuth resolution
h = 18 m ρ a = 1.5 m
range resolution
ρ r = 1.06
platform height
H = 3000 m
vertical baseline
Bv = 1 m
θ = 300
Bh = 10 m
2061 5
et al. / Q Procedia (2011) 205700– (2011) 2061 000–000 Huang SHuang Q, Liu Shiqi Z G, Zhang M, YuanEngineering Y / Procedia15Engineering
The polarimetric information and the scattering information of every antenna can be analysized through the polarimetric interferometry scattering matrix T6 , and it includes the amplitude and phase information of all channels. In experiments, assume that HV = VH , that is the symmetric target and they can exchange with each other. The definition of T6 is given by ⎡ T 11 ⎢T 21 ⎢ ⎢T 31 T6 = ⎢ ⎢T 41 ⎢T 51 ⎢ ⎣⎢T 61
T 12 T 13 T 14 T 15 T 16 ⎤ T 22 T 23 T 24 T 25 T 26 ⎥⎥ T 32 T 33 T 34 T 35 T 36 ⎥ ⎡ T11 ⎥=⎢ H T 42 T 43 T 44 T 45 T 46 ⎥ ⎢⎣Ω12 T 52 T 53 T 54 T 55 T 56 ⎥ ⎥ T 62 T 63 T 64 T 65 T 66 ⎦⎥
Ω12 ⎤ ⎥ T22 ⎥⎦
(10)
Through the analysis of the mentioned full polarimetric interferometry SAR imaging mechanism, choosing different polarimetric scattering mechanism ω1 and ω2 , six different polarimetric interferometry models can be obtained, i.e. HH interferometry, HV interferometry, VV interferometry, HH-VV interferometry, HH+VV interferometry and HV+VH interferometry. The phase center elevation estimations of six different polarimetric interferometry methods are shown in Fig.5. It can be seen from Fig.5 that the different polarimetric combination can obtain different polarimetric information and it is great in favor of improving the interferometric precision.
(a) HH (b) HV (c) VV (d) HH+VV (e) HH-VV (f) HV+VH Fig.5 The estimated results of the elevation information of different polarimetric interferometry center phase
5. Conclusions
The polarimetric interferometry SAR is one of the great important field which modern radars develop, it not only can supply abundant targtet information, but also obtain the DEM of a target, therefore, the applications is more and more wider. This paper mainly discusses the imaging mechanism of Pol-In-SAR and extracting the polarimetric interferometry information, what’s more, these information is explained from the scattering mechanism. References [1] Nord M E, et al.. Comparison of compact polarimetric synthetic aperture radar modes. IEEE Transactions on Geoscience and Remote Sensing, 2009, 47(1): 174-188. [2] Cloude S R and Pnpnthnnnssiou K P. Three-stage process for polnrimetric SAR
interferometriy. IEE Proceeding of
Radar Sonar Navigation, 2003, 150(3): 125-134. [3] Tan L L, Yank L B, Yang R L. Investigation on vegetation height retrieval technique with compact PolInSAR data. Journal of Electronics & Information Technology (In China), 2010, 32(12): 2814-2819. [4] Luo H M, Chen E X, Cheng J, Li X W. Forest height estimation methods using polarimetric SAR interferometry. Journal of Remote Sensing (In China), 2010, 14(4): 806-821. [5] Zhou M, Wang X H, Tang L L, Li C R. Developments and applications of polarimetric SAR interferometry techniques. Science and Technology Guide Report (In China), 2008, 26(21): 90-93. [6] Zou B, Zhang L M, Sun D M, Wang W. Information extraction using polarimetric interferometric SAR Data: Present and Future.. Journal of Electronics & Information Technology (In China), 2006, 28(10): 1979-1984.