The Wavenumber Shift in SAR Interferometry - Semantic Scholar
The Wavenumber Shift in SAR Interferometry Fabio Galelli, Andrea Monti Guarnieri. Francesco Parizzl, Paolo Pasquali, Claudio Prati, and Fabio Rocca
Abstrac/-SAR surveys from separate passes show relative shifts of the ground wavcnu m ber spectra thaI depend on the local slope and the off-nadir angle. We discuss the exploitation of this spectral sllift for different app] ications: I) generation of "low noise" intcrferograms benefiting phase unwrapping, 2) generation of quick-look interferograms, 3) decorrelation redllction by means of tunable SAl{ systems (TINSAR), 1 4) range resolution enhancement, and 5) the combination of SAR data gathered by different platforms (airborne and satell ite) for a "long-lime coherence" sludy.
1.
INTRODUCTION
AR interferomelry was introduced 20 years ago by
S
Graham I II, However, only afcer recent studie~ in Europe ano at the Jet Propulsion Laboratory, has its potential becll fully demonstrated. The growing interest in SAR interferomelry is also due to the impressive amount of data suitable for interferometry from the firSt European remote sensing satellite (ERS-I) and (he many airborne systems available. The information added by inlerferometry 10 delected SAR images is clearly shown in the example of Fig. 1 and 2. In Fig. 1, the ERS-l detected image of the area of Naples, ItUble a.!l a function of the 00 line Hhc difference 01 Ihe (omple, samples) as lolgnal For the saL:e of l.lmphmy lei us u..e the folio.... 10& appro'lm:'!lun 1C!.J. +.141
= :1(1..1.1
+ al·~ - .14.
11",1,
a
r\
- A(k
I-J
(J; , +
A.J
k:.::>1 J\ d..::
J.hoB. -8 VII. l,). tan
•n nl\
(\61
Here. VeA,. 1..) llo the re'\uh 01' Ihe double IOtegral. Thus. If we ha\'c ro.my Inlcrfemmelfl( llh~cn allan!> with different baselines. we can l.plll cach ob..cn'3I1nn A,O:, . .t:l mto n "l>urfacc contribution" A (A,. A ) :lnu U "volumelric contribution" proportional III lhe hu..cllllc; lhis lenn is proportional to the moment of the rcfiCCllVHy along the ..:: axi ..
AI1,.11 • All .. I)
J·h8~
- - .- VII,. II In.. (an 0
.rma.,,,
rofttrn.l'_ lma,c.&«;
_ .JUk • J; ) _ J !w:.18 ;;of _' • .::) c: 108 J~ e'(p
F" ' \"hllnc ~!flk"nl ~I. US I lrna,." larel col Bo>flIl'Iu"c ~ J"'I"1"C"'loCd I" IIoCPIr»IC cmwtnPft~" Pd voJlvrntllX C1lc..:n T,"P ~ 01 llle L,c,h "aIoiJ.... ~ ~ put" Roll_ I\Itld Udot .otuJlll:lfll.
(111
Fmm mo\(' obs.ervatlon~. It Il. then p.l\\lblc to dcri\'e an LM c\llmate of the ..urface and (he \'olumetr1\.' contribullOIb Juo;t IUo an eumple. \IX ERS-I un'e)" of me Bonn arca h.1\e been e,plolted for thl" i!( I afler n=g~lra lion tn pace and trequenC) The C'!>lU1lllIIed urfOs art' hmlon In Fig 7. The) are not reprc-.enled .... 11h" (he Qme '\Cale. 1Iince the a\crAge 3mpll1ud~ of the urf;l!,;e ronlnbutton IS roughl) 20 urnes that of the \olumetnL cuntnbuu n. A~ of )et. no delinl· tlve L"OflI:lu",on ha\C' bttn demed from thiS example. For ooe. II can be noted thJlthe \olumetnc conlribullon sho\loS loldelobe, nlended 10 the r.J.nge dlrectlon (\'ertlc:.l In the
UlJIII;dll tkJrU-.11 • ~ Lilli QJI1C' ncr
Image) Thl (eallut: comel. fmm !>Idelo~ of "'mng POint "C3uerers la) Ing on adJacenl range billS Due to me lopeCInti ..hilt compeno;atlon. the \Idelobc.. arc ph~ ~hl(ted .... lIh rt pC':et to (he maIO lobe. proponJonal both to the b.u.ellne .nd to Iheir dl'\UIOC'C' lrom the milln lobe. Hence. the) lend 10 be canceled from the "urfa(c comnbulJon • but leM"o from lhe volumetnc conlnbullon.:b far as the linear dcpha.. ing approAlmale.. a linear eh.mge propor· Ilonal to the baseline Different re,ulh (uuld N: obtuincd by rc~rcs"JOg wllh Ihe baselme pha ..e anl.! modulus JOstead of real lind IInagllllJry pam.. a.. ha~ been done JO lhis example. The concepti> have been checked wilh "ynlhclic l:xllmple.. that for hrc"ily arC' nOI reponed here and could be fUllher te"lcd by mean.!. of controlled c:paR of Ihe Iot)ovcr "lope 1\ lung enough Sho\H
n ugh lant mog am available ~ r rquen timali n nd fill rin ) In Fi . 8 lhe . P clrnl hift a a fun li n f lhe I . I I pi.. hown in the ca. f ERS-I wllh n ba. eline of m and a nommal offnadir angle of .. n ample e layover epararioD lth R -I data of mOunlaln u area in willerland i, . ho\ n In Fig. 9 11 I W nh n ting Lh.at there r a'e where onl a pama! :ep raIl n an be chle cd t. plcal exmple I repre em d by a lep fuo ti n al ng Ih range due 'lion. In uch a a e. \ e uld ha e thre c ntribuLieD from differenL regions ummcd at the !lam im rferogram po. ilion: the first f1aL l. n al the lever I vaLlon. the second flal lOne at the hIgher elevatIOn. and th 'lep transiuon. The ·tep lran.-iUon can be eparated from the th r LWO IOC 1\ h w a dilli r nl frequenc I Ih fnnge!>. H \ e r. lh' Iw f1al .lone h the same sp ctroJ shift and cannol bt:panned th r Ihan u ing a cend10 and de e ndin p e The lep ar'a w uld in a hadow. I f In ov r area euld b eparat d fr m Ih re t f the ima e. I pe in the range dIre ClOll from 0 10 9 0 (lOth r Ilh th e from -67 0 \0 .7 0 could b by ER -) in[erfer m \ with round pend nL nlope. a u uaJ M re r. b. e pI iting b th ascendin and de. ending ER -I pa.. e. ,almost 11:1 pc from 0 t +9 0 with hat cr azimuth orienLUti n are re vercd: lhi ilUa[ioD I ho n in Figure I . Th different urv f Fi . 10 Identify the .. I pe areca ere able fr m ER - I ( e ig 8) a. a unction IIf their azimuth ori nlalion ( e the I wer pan of I . 10). Thick nd thlD lin refer I a: ending and de. endin pa e. re pe II ely. Here. th ~ w comb," 11 n entati n Ihal c uld n I r h wn (bl ck areas . On th th r hand. if we able t d al With lao ver ar a', the n n b erv bination' would be more (the haded areas)
(i.e. .
D. A Tunable Interferomt'tric
R \'. (
4"10'
3
blind 8"511a
2
i, t:
z
i
o~~+-~-~-=------------tIow
U
~-1
en
-2
·3 ...L-.L----'--'-_-'"_ _"-_-'-_---'-L-L-''-_-'--_-'--' ~ ~ ~ ~ 0 W 00 00
LOCAL SlOPE (dag'-l
FIt!
pcclral shlfl
lunrnaJi r .Ihitude of the ai m with re pe I t I:. AT. the airborne R I king-an}8" hange more r.lpldl' han (J \ ilh the ground range \ (al< a uS! apr im Ii n 8, 'an ben Id rcd con. lam in :J few-hundred meter ulh). tn ther word. the band the ground Rectl\ II} pe trum c llected b E A T is aim I conslanl ith the ground range. wherea it rno e qUlle rapid I In Ih 81 muse. h lar t ground-ran e. ath ~\ lhat all w a partIal crlap of Ih I g und n livil.:p ctm can be c mpUI d from (6) In facI, the large. I .1110 cd °pectral hift I ~ Hz (in lhat c w h uld h n 10Hz frequem: rlap), r m I (With ex = 0). the angular eparatt n thaI rre ponL! I( _ 5 H.l spectral hi fl can mputed':::'O = 017 rad. The corresponding b g und-rung ulh is .l~'
FIg I
r "r tlk
Irna:~cJ
ar
,If Bunn
\ here H IS lh' re u. ed:
2IJaO =-c . 0,
irb m altitude. If lh
H= 0.•
=
Itt PIUl lIf 1\"" p been dbcu-llsed for the monostauc and blstatic SAR inlerferometer. Thl" relation has been ex· ploned to Improve well· known SAR Inlerferometry technlquell and 10 Inlroduce the idea of the tunable interfero· metric
Andrei MOllll GlIllrnlerl "'Il~ horn '" !t.lllIR. 11 II)', on Februlf)' 9, 1962 He n:,cl.cd the "Iftu· n:1-' ill c:1Cl:lron,c c:RI,lIttlln. fm", Pnhternleo dl MIlano In 191111. "'l1h • lhc30l~ on lite pll1,pltue Of-, hIler ban1. ,U'II(\II\1: Il'phcli IU l)'ntheur Ip cnllll' I'Id:u dill foclI\"" He tau b«n .... lIlt Ihe Depannlenl of ElCl:uume Eng,nccnng. Puht«lIllX1 d, MIlI.lln ~I",e 199B. D I member mille- SAil n:$ol'Ilth lei'" wllh Prul F
SAR
Fnlnc~o Plrlal Ina.lUllled III e1ectn..I' enll' II«n", frum lite Unl'enll" de,h itud, dl Gc:no"1 In 1990 lie I~ 11o"" wllh Pt11uecn,to dl Mllaoo. ""hen: he Iii "oBlnr 10"" ..nb hI' PI'a 0 decree HIt rllmnl relCuro;h ",l.l're"b ronrem SAil In Ic:rlemmelf) t«hnll,tuc. fOf OEM ,1enenuon. ~ml1l1 cru~1I1 mOllon nhmallon. and Image tCifIlllllon ImptD\'emcnl
ACKNOWLrDG\lENT
The authon. would like to than I. the reyie"'e~ for their useful ~ugge~tlons.
II] R CrlIhm 'i)nltk'lk; ,nll~r1em"""cr ...lb, ' ...r "'POIrlIph...· m.p PIn• .' P,., .. Il:.tl:.. \01 (l,~. pp 16)-768. JIIM l'n4 I~l A Gal>(1ellnJ R GfoldRell. ··Cmd(1'lIel lraJ J \1 Mamn "Tllwn- urad 1k~I.n 01 lnltrlCI\' rr\C',n, S)nlhl.lte lpenul'l' nda". IFF P".. PI F .J>] I \9. no 2, flP 1-11 I ~q ICl9~ 151 P Piau, IC Cue!. M !k)
Abstrac/-SAR surveys from separate passes show relative shifts of the ground wavcnu m ber spectra thaI depend on the local slope and the off-nadir angle. We discuss the exploitation of this spectral sllift for different app] ications: I) generation of "low noise" intcrferograms benefiting phase unwrapping, 2) generation of quick-look interferograms, 3) decorrelation redllction by means of tunable SAl{ systems (TINSAR), 1 4) range resolution enhancement, and 5) the combination of SAR data gathered by different platforms (airborne and satell ite) for a "long-lime coherence" sludy.
1.
INTRODUCTION
AR interferomelry was introduced 20 years ago by
S
Graham I II, However, only afcer recent studie~ in Europe ano at the Jet Propulsion Laboratory, has its potential becll fully demonstrated. The growing interest in SAR interferomelry is also due to the impressive amount of data suitable for interferometry from the firSt European remote sensing satellite (ERS-I) and (he many airborne systems available. The information added by inlerferometry 10 delected SAR images is clearly shown in the example of Fig. 1 and 2. In Fig. 1, the ERS-l detected image of the area of Naples, ItUble a.!l a function of the 00 line Hhc difference 01 Ihe (omple, samples) as lolgnal For the saL:e of l.lmphmy lei us u..e the folio.... 10& appro'lm:'!lun 1C!.J. +.141
= :1(1..1.1
+ al·~ - .14.
11",1,
a
r\
- A(k
I-J
(J; , +
A.J
k:.::>1 J\ d..::
J.hoB. -8 VII. l,). tan
•n nl\
(\61
Here. VeA,. 1..) llo the re'\uh 01' Ihe double IOtegral. Thus. If we ha\'c ro.my Inlcrfemmelfl( llh~cn allan!> with different baselines. we can l.plll cach ob..cn'3I1nn A,O:, . .t:l mto n "l>urfacc contribution" A (A,. A ) :lnu U "volumelric contribution" proportional III lhe hu..cllllc; lhis lenn is proportional to the moment of the rcfiCCllVHy along the ..:: axi ..
AI1,.11 • All .. I)
J·h8~
- - .- VII,. II In.. (an 0
.rma.,,,
rofttrn.l'_ lma,c.&«;
_ .JUk • J; ) _ J !w:.18 ;;of _' • .::) c: 108 J~ e'(p
F" ' \"hllnc ~!flk"nl ~I. US I lrna,." larel col Bo>flIl'Iu"c ~ J"'I"1"C"'loCd I" IIoCPIr»IC cmwtnPft~" Pd voJlvrntllX C1lc..:n T,"P ~ 01 llle L,c,h "aIoiJ.... ~ ~ put" Roll_ I\Itld Udot .otuJlll:lfll.
(111
Fmm mo\(' obs.ervatlon~. It Il. then p.l\\lblc to dcri\'e an LM c\llmate of the ..urface and (he \'olumetr1\.' contribullOIb Juo;t IUo an eumple. \IX ERS-I un'e)" of me Bonn arca h.1\e been e,plolted for thl" i!( I afler n=g~lra lion tn pace and trequenC) The C'!>lU1lllIIed urfOs art' hmlon In Fig 7. The) are not reprc-.enled .... 11h" (he Qme '\Cale. 1Iince the a\crAge 3mpll1ud~ of the urf;l!,;e ronlnbutton IS roughl) 20 urnes that of the \olumetnL cuntnbuu n. A~ of )et. no delinl· tlve L"OflI:lu",on ha\C' bttn demed from thiS example. For ooe. II can be noted thJlthe \olumetnc conlribullon sho\loS loldelobe, nlended 10 the r.J.nge dlrectlon (\'ertlc:.l In the
UlJIII;dll tkJrU-.11 • ~ Lilli QJI1C' ncr
Image) Thl (eallut: comel. fmm !>Idelo~ of "'mng POint "C3uerers la) Ing on adJacenl range billS Due to me lopeCInti ..hilt compeno;atlon. the \Idelobc.. arc ph~ ~hl(ted .... lIh rt pC':et to (he maIO lobe. proponJonal both to the b.u.ellne .nd to Iheir dl'\UIOC'C' lrom the milln lobe. Hence. the) lend 10 be canceled from the "urfa(c comnbulJon • but leM"o from lhe volumetnc conlnbullon.:b far as the linear dcpha.. ing approAlmale.. a linear eh.mge propor· Ilonal to the baseline Different re,ulh (uuld N: obtuincd by rc~rcs"JOg wllh Ihe baselme pha ..e anl.! modulus JOstead of real lind IInagllllJry pam.. a.. ha~ been done JO lhis example. The concepti> have been checked wilh "ynlhclic l:xllmple.. that for hrc"ily arC' nOI reponed here and could be fUllher te"lcd by mean.!. of controlled c:paR of Ihe Iot)ovcr "lope 1\ lung enough Sho\H
n ugh lant mog am available ~ r rquen timali n nd fill rin ) In Fi . 8 lhe . P clrnl hift a a fun li n f lhe I . I I pi.. hown in the ca. f ERS-I wllh n ba. eline of m and a nommal offnadir angle of .. n ample e layover epararioD lth R -I data of mOunlaln u area in willerland i, . ho\ n In Fig. 9 11 I W nh n ting Lh.at there r a'e where onl a pama! :ep raIl n an be chle cd t. plcal exmple I repre em d by a lep fuo ti n al ng Ih range due 'lion. In uch a a e. \ e uld ha e thre c ntribuLieD from differenL regions ummcd at the !lam im rferogram po. ilion: the first f1aL l. n al the lever I vaLlon. the second flal lOne at the hIgher elevatIOn. and th 'lep transiuon. The ·tep lran.-iUon can be eparated from the th r LWO IOC 1\ h w a dilli r nl frequenc I Ih fnnge!>. H \ e r. lh' Iw f1al .lone h the same sp ctroJ shift and cannol bt:panned th r Ihan u ing a cend10 and de e ndin p e The lep ar'a w uld in a hadow. I f In ov r area euld b eparat d fr m Ih re t f the ima e. I pe in the range dIre ClOll from 0 10 9 0 (lOth r Ilh th e from -67 0 \0 .7 0 could b by ER -) in[erfer m \ with round pend nL nlope. a u uaJ M re r. b. e pI iting b th ascendin and de. ending ER -I pa.. e. ,almost 11:1 pc from 0 t +9 0 with hat cr azimuth orienLUti n are re vercd: lhi ilUa[ioD I ho n in Figure I . Th different urv f Fi . 10 Identify the .. I pe areca ere able fr m ER - I ( e ig 8) a. a unction IIf their azimuth ori nlalion ( e the I wer pan of I . 10). Thick nd thlD lin refer I a: ending and de. endin pa e. re pe II ely. Here. th ~ w comb," 11 n entati n Ihal c uld n I r h wn (bl ck areas . On th th r hand. if we able t d al With lao ver ar a', the n n b erv bination' would be more (the haded areas)
(i.e. .
D. A Tunable Interferomt'tric
R \'. (
4"10'
3
blind 8"511a
2
i, t:
z
i
o~~+-~-~-=------------tIow
U
~-1
en
-2
·3 ...L-.L----'--'-_-'"_ _"-_-'-_---'-L-L-''-_-'--_-'--' ~ ~ ~ ~ 0 W 00 00
LOCAL SlOPE (dag'-l
FIt!
pcclral shlfl
lunrnaJi r .Ihitude of the ai m with re pe I t I:. AT. the airborne R I king-an}8" hange more r.lpldl' han (J \ ilh the ground range \ (al< a uS! apr im Ii n 8, 'an ben Id rcd con. lam in :J few-hundred meter ulh). tn ther word. the band the ground Rectl\ II} pe trum c llected b E A T is aim I conslanl ith the ground range. wherea it rno e qUlle rapid I In Ih 81 muse. h lar t ground-ran e. ath ~\ lhat all w a partIal crlap of Ih I g und n livil.:p ctm can be c mpUI d from (6) In facI, the large. I .1110 cd °pectral hift I ~ Hz (in lhat c w h uld h n 10Hz frequem: rlap), r m I (With ex = 0). the angular eparatt n thaI rre ponL! I( _ 5 H.l spectral hi fl can mputed':::'O = 017 rad. The corresponding b g und-rung ulh is .l~'
FIg I
r "r tlk
Irna:~cJ
ar
,If Bunn
\ here H IS lh' re u. ed:
2IJaO =-c . 0,
irb m altitude. If lh
H= 0.•
=
Itt PIUl lIf 1\"" p been dbcu-llsed for the monostauc and blstatic SAR inlerferometer. Thl" relation has been ex· ploned to Improve well· known SAR Inlerferometry technlquell and 10 Inlroduce the idea of the tunable interfero· metric
Andrei MOllll GlIllrnlerl "'Il~ horn '" !t.lllIR. 11 II)', on Februlf)' 9, 1962 He n:,cl.cd the "Iftu· n:1-' ill c:1Cl:lron,c c:RI,lIttlln. fm", Pnhternleo dl MIlano In 191111. "'l1h • lhc30l~ on lite pll1,pltue Of-, hIler ban1. ,U'II(\II\1: Il'phcli IU l)'ntheur Ip cnllll' I'Id:u dill foclI\"" He tau b«n .... lIlt Ihe Depannlenl of ElCl:uume Eng,nccnng. Puht«lIllX1 d, MIlI.lln ~I",e 199B. D I member mille- SAil n:$ol'Ilth lei'" wllh Prul F
SAR
Fnlnc~o Plrlal Ina.lUllled III e1ectn..I' enll' II«n", frum lite Unl'enll" de,h itud, dl Gc:no"1 In 1990 lie I~ 11o"" wllh Pt11uecn,to dl Mllaoo. ""hen: he Iii "oBlnr 10"" ..nb hI' PI'a 0 decree HIt rllmnl relCuro;h ",l.l're"b ronrem SAil In Ic:rlemmelf) t«hnll,tuc. fOf OEM ,1enenuon. ~ml1l1 cru~1I1 mOllon nhmallon. and Image tCifIlllllon ImptD\'emcnl
ACKNOWLrDG\lENT
The authon. would like to than I. the reyie"'e~ for their useful ~ugge~tlons.
II] R CrlIhm 'i)nltk'lk; ,nll~r1em"""cr ...lb, ' ...r "'POIrlIph...· m.p PIn• .' P,., .. Il:.tl:.. \01 (l,~. pp 16)-768. JIIM l'n4 I~l A Gal>(1ellnJ R GfoldRell. ··Cmd(1'lIel lraJ J \1 Mamn "Tllwn- urad 1k~I.n 01 lnltrlCI\' rr\C',n, S)nlhl.lte lpenul'l' nda". IFF P".. PI F .J>] I \9. no 2, flP 1-11 I ~q ICl9~ 151 P Piau, IC Cue!. M !k)
