Theoretical Analysis and Applications of Tomographic SAR Imaging
TELKOMNIKA, Vol.14, No.2A, June 2016, pp. 217~222
ISSN: 1693-6930, accredited A by DIKTI, Decree No: 58/DIKTI/Kep/2013
DOI: 10.12928/TELKOMNIKA.v14i2A.4325
217
Theoretical Analysis and Applications of Tomographic
SAR Imaging
Liu Hui*, Wu Jianjiang, Li Ling, Li Zhizhe
Department of Electrical and Information Engineering, Beijing University of Civil Engineering and
Architecture, Beijing, 100044, China
*Corresponding author, e-mail: [email protected]
Abstract
Tomographic Synthetic Aperture Radar extends the traditional 2D SAR imaging to multi
dimension imaging by reconstructing the real scene of SAR sensor on the ground. It is very important to
realize the 3D mapping of urban areas, the identification of artificial targets and so on. The mathematical
model of Tomographic SAR Imaging is deduced and its significance in physics are introduced herein, then
the resolution ability in nsr direction is analyzed. At last, the applications of tomographic SAR imaging
technology are prospected.
Keywords: Tomographic SAR; SAR three-dimensional imaging; Tomographic SAR imaging algorithm
1. Introduction
Tomographic Synthetic Aperture Radar Imaging Technology (Tomographic Synthetic
Aperture Radar, referred to as TomoSAR or SAR Tomography) is remote sensing means which
extends theory of imaging technology of two-dimension in tradition to height dimension, gaining
ground three-dimensional information. Different from Interferometric SAR, Tomographic SAR
Three-dimensional Imaging Technology adopts the idea of height dimension synthetic aperture
to solve problem of several base lines interference, realizing resolution capability of height
dimension [1, 2]. In the early of 90s of last century, Tomographic Technology has been brought
in SAR field. But image data which can be used for research was rare. With levitation of a new
generation high resolution satellite in succession after 2007, a large number of high-quality SAR
tomographic image was provided Error! Reference source not found.. Density of scatterer with
high resolution data increased rapidly, and signal to noise ratio improved sharply. Compared
with original medium resolution ratio data, it is more suitable to carry out SAR tomographic
research. Tomographic SAR Imaging Technology provides above rubies technical support in
terms of fine application of topographic surveys of high precision, accurate assessment of
disasters, dynamic monitoring of topography, three-dimensional reconstruction of urban region
etc. Several base lines SAR Tomographic Imaging Technology becomes research direction
which is relatively hot in present SAR field.
2. Theoretical Analysis to Tomographic SAR Model
2.1. Mathematic Model and Physical Significance of Tomographic SAR
Geometric model of Tomographic SAR is as shown in Figure 1, where direction of S is
Normal-Slant Range (referred to as NSR, i.e. height direction), and b is parallel with height
direction, showing position of synthetic aperture.
Received January 26, 2016; Revised April 29, 2016; Accepted May 15, 2016
218
ISSN: 1693-6930
Figure 1. Geometric model of tomographic SAR Error! Reference source not found.
bn
Sn
bn
Rni
Sm
s
r
Pi ( r , si )
P0 (r , s0 )
Figure 2. Analysis graphics about tomographic SAR principle
As shown in Figure 2, supposing S m as main satellite, image gained as g m , and g n as
synthetic aperture radar image gained by satellite S n , then
K
g n i exp( j
i 0
4
Rni )
(1)
i ( i 0,1, , K ) is rear scattering coefficient of scattering point Pi
( i 0,1, , K )in Normal-Slant Range of S direction. Rni ( i 0,1, , K ) is distance of
scattering point Pi ( i 0,1, , K ) in Normal-Slant Range of S direction to satellite S n . is
wave length of radar. K is number of scattering point in Normal-Slant Range of S direction.
In the formula (1),
According to geometrical relationship in Figure 2, it is
Rni (r bn ) 2 ( si bn )2
i 0,1, , K
TELKOMNIKA Vol. 14, No. 2A, June 2016 : 217 – 222
(2)
TELKOMNIKA
ISSN: 1693-6930
219
In the formula (2), si ( i 0,1, , K ) is distance of scattering point Pi in Normal-Slant
Range of S direction to reference point P0 . r is distance of main satellite S m to Normal-Slant
Range of S direction. bn / / and bn are components of vertical track base line between satellite
Sn to main satellite S m in Slant Range r direction and Normal-Slant Range of S direction.
According to geometrical relationship in Figure 2 and taylor expansion of function, formula (2) is
approximate to
Rni ( r bn )
( si bn ) 2
2( r bn )
i 0,1, , K
(3)
For r bn , formula (3) can be written as
R ni r
( s i bn ) 2
2r
i 0,1, , K
Supposing that formula (1) is multiplied by plural factor
Gn g n exp(
4
(4)
exp(
4
Rn 0 ) , and
Rn 0 ) , then it is
K
Gn i exp[ j
i 0
4
( Rni Rn 0 )]
(5)
Where, Rn 0 is slant-range of reference point P0 in Normal-Slant Range of S direction
to satellite S n . Supposing that coordinate value of reference point P0 in Normal-Slant Range of
S direction is s0 0 , then it is
bn 2
Rn 0 r
2r
(6)
Further we can get
R ni R n 0
bn
s2
si i
r
2r
i 0,1, , K
(7)
So, formula (5) can be changed to
K
Gn i exp[ j
4
(
bn
s2
si i )]
2r
r
K
2 si 2
2b
= i exp( j
) exp( j 2 n si )
r
r
i0
i0
Supposing
( si ) i exp( j
(8)
2 si 2
) , and define it as repeated backscattering
r
coefficient of target Pi , and then formula (8) can be simplified as the following form
Theoretical Analysis and Applications of Tomographic SAR Imaging (Liu Hui)
220
ISSN: 1693-6930
Gn
K
( s ) exp( j 2
i
i0
Supposing f n
(9)
2 bn
, then formula (9) is
r
Gn DFT[ ( si )] f f
In formula (10),
2 bn
s)
r i
(10)
n
DFT[] is discrete Fourier transform operation. So, above derivation
process shows that Gn is result of discrete Fourier transform of repeated backscattering
coefficient of Normal-Slant Range target in frequency f n . We know that different position of
satellite corresponds to different vertical base lines. Coming here, we can get the conclusion
that satellite position which is distributed on base lines has something to do with frequency
domain distribution of Normal-Slant Range target scattering point. Corresponding frequency is
relevant with base lines. If it is written in the form of continuous signal, it is
Gn ( s ) exp( j 2 f n s )ds
(11)
Gn represents that frequency component is image of f n . When image registration of
enough images with different frequency component is finished, its sequence can be seen as
Fourier transform of distribution function ( s ) of scattering coefficient of Normal-Slant Range
target. For Fourier inverse transform, information of distribution function
coefficient of Normal-Slant Range target can be gained immediately.
(s)
of scattering
2.2. Resolution Capability Analysis on Tomographic SAR in Normal-Slant Range Error!
Reference source not found.
When vertical base lines are sampled uniformly and sample interval is b , then
f
2 b
r
(12)
According to theorem of Nyquist, when sample interval of frequency domain is
time domain range which can be reconstructed without fuzziness is
f ,
2t 1 f . Applied to
above process, reconstructed range 2smax (without fuzziness and with Normal-Slant Range) is
2smax
r
(13)
2b
[ smax , smax ] is span of Normal-Slant Range. Its equivalent synthetic aperture length in
Normal-Slant Range depends on span B of vertical base lines. So image sequence can be
specifically written as
Gn
smax
smax
( s) exp( j 2 f n s)ds
(14)
Rayleigh resolution ratio of Normal-Slant Range which is corresponding to equivalent
synthetic aperture is
TELKOMNIKA Vol. 14, No. 2A, June 2016 : 217 – 222
TELKOMNIKA
s
2B
r
ISSN: 1693-6930
221
(15)
3. Results and Discussion
In recent years, with constant launch of satellite borne SAR satellite, data precision
which can be used for Tomographic SAR applied research is higher and higher, and applied
research of Tomographic SAR technology in many fields is being carried out [5-8]. For example,
many research findings Error! Reference source not found. have been gained in elevation
reconstruction of urban architecture, height of man-made target and extraction of shape change
parameter, early warning in urban s
3.1. Reconstruction of Urban Building Elevation
Data set used in Tomographic SAR is all from same side of target. So Tomographic
SAR can be carried out only in part elevation of building, i.e. building elevation shined by SAR.
With stored quantity of SAR data becoming richer and richer, Tomographic SAR data set in
different angles of the same area is richer and richer, bringing opportunity to three-dimensional
reconstruction of total building elevation. Condition near urban architecture is complex, so
adopting means of SAR to realize reconstruction is a challenging research. Appearance of
Tomographic SAR makes effectiveness of application of microwave remote sensing means
improved to a higher level. Previously, workers engaged in SAR technology research carried out
many researches that adopted SAR images in aspect of urban building. One kind of method is
to detect and extract building Error! Reference source not found. from single SAR image Error!
Reference source not found. or by using Interferometric SAR. But these methods failed to realize
reconstruction of height dimension. They are all SAR images shined from same side of building
and it is impossible to gain elevation not shined in building. Technology of research on building
reconstruction by adopting several angles InSAR Error! Reference source not found. was put
forward, but complex urban scene and existence of speckle effect and layover effect which was
immanent in SAR image made above researches limited to building reconstruction in a certain
extent.
With acquisition of data of high resolution satellite borne SAR and appearance of
Duohangguo In SAR technology, permanent scatterer InSAR technology and even TomoSAR
technology, accurate three-dimensional reconstruction can be realized aimed at individual
building in complicated background. Up to now, Zhu Xiaoxiang and Shahzad have carried out
fruitful research [12, 13] in this aspect, and Zhu Xiaoxiang etc. have used multi-angles
Tomographic SAR to gain building elevation point cloud of Hotel Bellagio in Las Vegas in
America.
3.2. Running Parameter Extraction of Objects on the Ground
Using Three-dimensional Tomographic SAR Technology can gain height information of
objects in ground. Using Multi-dimensional Tomographic SAR can gain shape change
information of objects in ground. Through Tomography in height dimension and time dimension,
height and shape change speed information can be gained. For example, in city, with time going
by, slow movement of building facilities and thermal expansion range etc. parameter can be
extracted through different tomography. Tomographic SAR difference imaging is the typical
multi-dimensional Tomographic SAR imaging.
What’s more, global glacier change (including mountain land glacier, polar glacier, sea
ice etc.) has important denotative significance on the researches in field of climatic environment
and water resource. SAR Tomographic Technology can be used to extract fault construction of
glacier in different seasons, so thickness of glacier can be evaluated. Movement Error!
Reference source not found. of global glacier can be monitored through thickness change of ice
layer every year.
3.3. Evaluation of Biomass on Vegetation
Evaluation of biomass on vegetation is of great importance to ecosystem assessment,
atmosphere and environmental pollution etc. research. It spends a lot of time and energy to
evaluate biomass on artificial vegetation of extensiveness. Tomographic SAR Technology can
invert vertically scattered power spectrum of forest directly from radar imaging angle. That is to
invert upward scattering intensity of forest in different height, thus extracting height, density etc.
Theoretical Analysis and Applications of Tomographic SAR Imaging (Liu Hui)
222
ISSN: 1693-6930
information of forest through position of scattering central point and scattering intensity,
providing effective parameter for evaluation of biomass. Because appropriate scattering
mechanism of vegetation relies deeply on polarization mode, tomographic representation under
different polarization modes is usually adopted to improve precision of parameter estimation.
Compared with application of SAR tomography in city, its potential in aspect of biomass
estimation is greater Error! Reference source not found..
4. Conclusion
SAR tomography expands traditional bidimensional SAR image to multidimensional
imaging by rebuilding real scenario where SAR sensor shines ground, which provides above
rubies technical support in terms of fine application of topographic surveys of high precision,
accurate assessment of disasters, dynamic monitoring of topography, three-dimensional
reconstruction of urban region and biomass estimation of vegetation etc. This paper deduces
mathematic model of Tomographic SAR, showing its physical significance, and analyzing
resolving power of Tomographic SAR Normal-Slant Range. At last it introduces major
application fields of Tomographic SAR at present. I hope this paper can make more scholars
know about application fields of this technology, continually expanding direction of application of
the technology.
Acknowledgements
The National Natural Science Foundation Foundation of China under Grant No.
61501019. The open research fund program of Beijing key laboratory of robot bionics and
function research (Grant No.07080915001).
References
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
[9]
[10]
[11]
[12]
[13]
[14]
[15]
Pang Bo, Dai Dahai, Xing Shiqi, Wang Xuesong, Liu Qingfu. Development and Prospect of SAR
Tomographic Technology. System Engineering and Electronic Technique. 2013; 35(7): 1421-1429.
Subchan SS. A direct multiple shooting method for missile trajectory optimization with the terminal
bunt manoeuvre. IPTEK The Journal for Technology and Science. 2011; 22(3): 147-151.
Liao Mingsheng, Wei Lianhuan, BALZ Timo (Germany), Zhang Lu. Application of TomoSAR
Technology in Urban Shape Change Monitoring. Shanghai Territorial Resources. 2013; 34(4): 7-16.
Sun Xilong, Yu Anxi, Dong Zhen, Sun Zaoyu, Liang Dianlong. SAR Tomographic Method with High
Resolution. Journal of National University of Defense Technology. 2012; 34(3): 125-130.
Wei Lianhuan, Liao Mingsheng, BALZ Timo, Zhang Lu. Extraction of Building Layover Scatterer by
SAR Tomographic Method with High Resolution. Forum of Information Science in Journal of Wuhan
University. 2014; 39(5): 536-540.
Zhang Fubo, Liu Mei. SAR Tomographic Algorithm based on Frequency Domain Least Squares
APES and Inhomogeneous Multi-baselines. Journal of Electronics and Information. 2012; 34(7):
1568-1573.
Ren Xiaozhen, Yang Ruliang. RELAX Improved Algorithm of SAR Tomography. Data Acquisition and
Processing. 2010; 25(3): 302-306.
Cui Y, Zhang S, Chen Z, Zheng W. A New Digital Image Hiding Algorithm Based on Wavelet Packet
Transform and Singular Value Decomposition. TELKOMNIKA Indonesian Journal of Electrical
Engineering. 2014; 12(7): 5408-5413.
Dadkhah M, Obeidat MM, Jazi MD, Sutikno T, Riyadi MA. How Can We Identify Hijacked journals?
Bulletin of Electrical Engineering and Informatics. 2015; 4(2): 83-87.
K Firdausy, T Sutikno, E Prasetyo. Image enhancement using contrast stretching on RGB and IHS
digital image. TELKOMNIKA (Telecommunication Computing Electronics and Control). 2007; 5 (1):
45-50.
Lv Z, Halawani A, Fen S. Touch-less Interactive Augmented Reality Game on Vision Based
Wearable Device. Personal and Ubiquitous Computing. 2015; 19(3): 551-567.
Guanqun Bao, Liang Mi, Yishuang Geng, Mingda Zhou, Kaveh Pahlavan. A video-based speed
estimation technique for localizing the wireless capsule endoscope inside gastrointestinal tract. 2014
36th Annual International Conference of the IEEE Engineering in Medicine and Biology Society.
IEEE. 2014: 5615-5618.
Degui Zeng, Yishuang Geng. Content distribution mechanism in mobile P2P network. Journal of
Networks. 2014; 9(5): 1229-1236.
Gu W, Lv Z, Hao M. Change detection method for remote sensing images based on an improved
Markov random field. Multimedia Tools and Applications. 2015: 1-16.
Chen Z, Huang W, Lv Z. Towards a face recognition method based on uncorrelated discriminant
sparse preserving projection. Multimedia Tools and Applications. 2015: 1-15.
TELKOMNIKA Vol. 14, No. 2A, June 2016 : 217 – 222
ISSN: 1693-6930, accredited A by DIKTI, Decree No: 58/DIKTI/Kep/2013
DOI: 10.12928/TELKOMNIKA.v14i2A.4325
217
Theoretical Analysis and Applications of Tomographic
SAR Imaging
Liu Hui*, Wu Jianjiang, Li Ling, Li Zhizhe
Department of Electrical and Information Engineering, Beijing University of Civil Engineering and
Architecture, Beijing, 100044, China
*Corresponding author, e-mail: [email protected]
Abstract
Tomographic Synthetic Aperture Radar extends the traditional 2D SAR imaging to multi
dimension imaging by reconstructing the real scene of SAR sensor on the ground. It is very important to
realize the 3D mapping of urban areas, the identification of artificial targets and so on. The mathematical
model of Tomographic SAR Imaging is deduced and its significance in physics are introduced herein, then
the resolution ability in nsr direction is analyzed. At last, the applications of tomographic SAR imaging
technology are prospected.
Keywords: Tomographic SAR; SAR three-dimensional imaging; Tomographic SAR imaging algorithm
1. Introduction
Tomographic Synthetic Aperture Radar Imaging Technology (Tomographic Synthetic
Aperture Radar, referred to as TomoSAR or SAR Tomography) is remote sensing means which
extends theory of imaging technology of two-dimension in tradition to height dimension, gaining
ground three-dimensional information. Different from Interferometric SAR, Tomographic SAR
Three-dimensional Imaging Technology adopts the idea of height dimension synthetic aperture
to solve problem of several base lines interference, realizing resolution capability of height
dimension [1, 2]. In the early of 90s of last century, Tomographic Technology has been brought
in SAR field. But image data which can be used for research was rare. With levitation of a new
generation high resolution satellite in succession after 2007, a large number of high-quality SAR
tomographic image was provided Error! Reference source not found.. Density of scatterer with
high resolution data increased rapidly, and signal to noise ratio improved sharply. Compared
with original medium resolution ratio data, it is more suitable to carry out SAR tomographic
research. Tomographic SAR Imaging Technology provides above rubies technical support in
terms of fine application of topographic surveys of high precision, accurate assessment of
disasters, dynamic monitoring of topography, three-dimensional reconstruction of urban region
etc. Several base lines SAR Tomographic Imaging Technology becomes research direction
which is relatively hot in present SAR field.
2. Theoretical Analysis to Tomographic SAR Model
2.1. Mathematic Model and Physical Significance of Tomographic SAR
Geometric model of Tomographic SAR is as shown in Figure 1, where direction of S is
Normal-Slant Range (referred to as NSR, i.e. height direction), and b is parallel with height
direction, showing position of synthetic aperture.
Received January 26, 2016; Revised April 29, 2016; Accepted May 15, 2016
218
ISSN: 1693-6930
Figure 1. Geometric model of tomographic SAR Error! Reference source not found.
bn
Sn
bn
Rni
Sm
s
r
Pi ( r , si )
P0 (r , s0 )
Figure 2. Analysis graphics about tomographic SAR principle
As shown in Figure 2, supposing S m as main satellite, image gained as g m , and g n as
synthetic aperture radar image gained by satellite S n , then
K
g n i exp( j
i 0
4
Rni )
(1)
i ( i 0,1, , K ) is rear scattering coefficient of scattering point Pi
( i 0,1, , K )in Normal-Slant Range of S direction. Rni ( i 0,1, , K ) is distance of
scattering point Pi ( i 0,1, , K ) in Normal-Slant Range of S direction to satellite S n . is
wave length of radar. K is number of scattering point in Normal-Slant Range of S direction.
In the formula (1),
According to geometrical relationship in Figure 2, it is
Rni (r bn ) 2 ( si bn )2
i 0,1, , K
TELKOMNIKA Vol. 14, No. 2A, June 2016 : 217 – 222
(2)
TELKOMNIKA
ISSN: 1693-6930
219
In the formula (2), si ( i 0,1, , K ) is distance of scattering point Pi in Normal-Slant
Range of S direction to reference point P0 . r is distance of main satellite S m to Normal-Slant
Range of S direction. bn / / and bn are components of vertical track base line between satellite
Sn to main satellite S m in Slant Range r direction and Normal-Slant Range of S direction.
According to geometrical relationship in Figure 2 and taylor expansion of function, formula (2) is
approximate to
Rni ( r bn )
( si bn ) 2
2( r bn )
i 0,1, , K
(3)
For r bn , formula (3) can be written as
R ni r
( s i bn ) 2
2r
i 0,1, , K
Supposing that formula (1) is multiplied by plural factor
Gn g n exp(
4
(4)
exp(
4
Rn 0 ) , and
Rn 0 ) , then it is
K
Gn i exp[ j
i 0
4
( Rni Rn 0 )]
(5)
Where, Rn 0 is slant-range of reference point P0 in Normal-Slant Range of S direction
to satellite S n . Supposing that coordinate value of reference point P0 in Normal-Slant Range of
S direction is s0 0 , then it is
bn 2
Rn 0 r
2r
(6)
Further we can get
R ni R n 0
bn
s2
si i
r
2r
i 0,1, , K
(7)
So, formula (5) can be changed to
K
Gn i exp[ j
4
(
bn
s2
si i )]
2r
r
K
2 si 2
2b
= i exp( j
) exp( j 2 n si )
r
r
i0
i0
Supposing
( si ) i exp( j
(8)
2 si 2
) , and define it as repeated backscattering
r
coefficient of target Pi , and then formula (8) can be simplified as the following form
Theoretical Analysis and Applications of Tomographic SAR Imaging (Liu Hui)
220
ISSN: 1693-6930
Gn
K
( s ) exp( j 2
i
i0
Supposing f n
(9)
2 bn
, then formula (9) is
r
Gn DFT[ ( si )] f f
In formula (10),
2 bn
s)
r i
(10)
n
DFT[] is discrete Fourier transform operation. So, above derivation
process shows that Gn is result of discrete Fourier transform of repeated backscattering
coefficient of Normal-Slant Range target in frequency f n . We know that different position of
satellite corresponds to different vertical base lines. Coming here, we can get the conclusion
that satellite position which is distributed on base lines has something to do with frequency
domain distribution of Normal-Slant Range target scattering point. Corresponding frequency is
relevant with base lines. If it is written in the form of continuous signal, it is
Gn ( s ) exp( j 2 f n s )ds
(11)
Gn represents that frequency component is image of f n . When image registration of
enough images with different frequency component is finished, its sequence can be seen as
Fourier transform of distribution function ( s ) of scattering coefficient of Normal-Slant Range
target. For Fourier inverse transform, information of distribution function
coefficient of Normal-Slant Range target can be gained immediately.
(s)
of scattering
2.2. Resolution Capability Analysis on Tomographic SAR in Normal-Slant Range Error!
Reference source not found.
When vertical base lines are sampled uniformly and sample interval is b , then
f
2 b
r
(12)
According to theorem of Nyquist, when sample interval of frequency domain is
time domain range which can be reconstructed without fuzziness is
f ,
2t 1 f . Applied to
above process, reconstructed range 2smax (without fuzziness and with Normal-Slant Range) is
2smax
r
(13)
2b
[ smax , smax ] is span of Normal-Slant Range. Its equivalent synthetic aperture length in
Normal-Slant Range depends on span B of vertical base lines. So image sequence can be
specifically written as
Gn
smax
smax
( s) exp( j 2 f n s)ds
(14)
Rayleigh resolution ratio of Normal-Slant Range which is corresponding to equivalent
synthetic aperture is
TELKOMNIKA Vol. 14, No. 2A, June 2016 : 217 – 222
TELKOMNIKA
s
2B
r
ISSN: 1693-6930
221
(15)
3. Results and Discussion
In recent years, with constant launch of satellite borne SAR satellite, data precision
which can be used for Tomographic SAR applied research is higher and higher, and applied
research of Tomographic SAR technology in many fields is being carried out [5-8]. For example,
many research findings Error! Reference source not found. have been gained in elevation
reconstruction of urban architecture, height of man-made target and extraction of shape change
parameter, early warning in urban s
3.1. Reconstruction of Urban Building Elevation
Data set used in Tomographic SAR is all from same side of target. So Tomographic
SAR can be carried out only in part elevation of building, i.e. building elevation shined by SAR.
With stored quantity of SAR data becoming richer and richer, Tomographic SAR data set in
different angles of the same area is richer and richer, bringing opportunity to three-dimensional
reconstruction of total building elevation. Condition near urban architecture is complex, so
adopting means of SAR to realize reconstruction is a challenging research. Appearance of
Tomographic SAR makes effectiveness of application of microwave remote sensing means
improved to a higher level. Previously, workers engaged in SAR technology research carried out
many researches that adopted SAR images in aspect of urban building. One kind of method is
to detect and extract building Error! Reference source not found. from single SAR image Error!
Reference source not found. or by using Interferometric SAR. But these methods failed to realize
reconstruction of height dimension. They are all SAR images shined from same side of building
and it is impossible to gain elevation not shined in building. Technology of research on building
reconstruction by adopting several angles InSAR Error! Reference source not found. was put
forward, but complex urban scene and existence of speckle effect and layover effect which was
immanent in SAR image made above researches limited to building reconstruction in a certain
extent.
With acquisition of data of high resolution satellite borne SAR and appearance of
Duohangguo In SAR technology, permanent scatterer InSAR technology and even TomoSAR
technology, accurate three-dimensional reconstruction can be realized aimed at individual
building in complicated background. Up to now, Zhu Xiaoxiang and Shahzad have carried out
fruitful research [12, 13] in this aspect, and Zhu Xiaoxiang etc. have used multi-angles
Tomographic SAR to gain building elevation point cloud of Hotel Bellagio in Las Vegas in
America.
3.2. Running Parameter Extraction of Objects on the Ground
Using Three-dimensional Tomographic SAR Technology can gain height information of
objects in ground. Using Multi-dimensional Tomographic SAR can gain shape change
information of objects in ground. Through Tomography in height dimension and time dimension,
height and shape change speed information can be gained. For example, in city, with time going
by, slow movement of building facilities and thermal expansion range etc. parameter can be
extracted through different tomography. Tomographic SAR difference imaging is the typical
multi-dimensional Tomographic SAR imaging.
What’s more, global glacier change (including mountain land glacier, polar glacier, sea
ice etc.) has important denotative significance on the researches in field of climatic environment
and water resource. SAR Tomographic Technology can be used to extract fault construction of
glacier in different seasons, so thickness of glacier can be evaluated. Movement Error!
Reference source not found. of global glacier can be monitored through thickness change of ice
layer every year.
3.3. Evaluation of Biomass on Vegetation
Evaluation of biomass on vegetation is of great importance to ecosystem assessment,
atmosphere and environmental pollution etc. research. It spends a lot of time and energy to
evaluate biomass on artificial vegetation of extensiveness. Tomographic SAR Technology can
invert vertically scattered power spectrum of forest directly from radar imaging angle. That is to
invert upward scattering intensity of forest in different height, thus extracting height, density etc.
Theoretical Analysis and Applications of Tomographic SAR Imaging (Liu Hui)
222
ISSN: 1693-6930
information of forest through position of scattering central point and scattering intensity,
providing effective parameter for evaluation of biomass. Because appropriate scattering
mechanism of vegetation relies deeply on polarization mode, tomographic representation under
different polarization modes is usually adopted to improve precision of parameter estimation.
Compared with application of SAR tomography in city, its potential in aspect of biomass
estimation is greater Error! Reference source not found..
4. Conclusion
SAR tomography expands traditional bidimensional SAR image to multidimensional
imaging by rebuilding real scenario where SAR sensor shines ground, which provides above
rubies technical support in terms of fine application of topographic surveys of high precision,
accurate assessment of disasters, dynamic monitoring of topography, three-dimensional
reconstruction of urban region and biomass estimation of vegetation etc. This paper deduces
mathematic model of Tomographic SAR, showing its physical significance, and analyzing
resolving power of Tomographic SAR Normal-Slant Range. At last it introduces major
application fields of Tomographic SAR at present. I hope this paper can make more scholars
know about application fields of this technology, continually expanding direction of application of
the technology.
Acknowledgements
The National Natural Science Foundation Foundation of China under Grant No.
61501019. The open research fund program of Beijing key laboratory of robot bionics and
function research (Grant No.07080915001).
References
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
[9]
[10]
[11]
[12]
[13]
[14]
[15]
Pang Bo, Dai Dahai, Xing Shiqi, Wang Xuesong, Liu Qingfu. Development and Prospect of SAR
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Subchan SS. A direct multiple shooting method for missile trajectory optimization with the terminal
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