Synthetic Aperture Radar Processing

Transcript

1 Synthetic Apetue Rd Pocessing SAR nd IFSAR Giogio Fnceschetti Univesit Fedeico II Npoli Itly 1

2 REFERENCE TEXT Giogio Fnceschetti Riccdo Lni SYNTHETIC APERTURE RADAR PROCESSING TECHNIQUES CRC Pess BOCA RATON Fl 1999

3 3

4 Tle of content Bsic concepts Pocessing Intefeometic SAR 4

5 Bsic Concepts Geomety Response in Time Domin Response in Fequency Domin 5

6 I. Geomety 1. Cylindicl efeence coodinte system 6

7 . Boesight stip mode illumintion geomety 7

8 3. Boesight cquisition geomety in the () plne 8

9 9 II. SAR esponse in time-domin 1. Tnsmitted wvefom fo the chip cse () ( ) ( ) τ ω n n t t t t P t j t f ect ep 1 ( ) ( ) α ep n n t t j t t P

10 1. Received wvefom fom unity sctteed t fte heteodine with ( ) [ ] w c R t t c R t t P c R j t t f n n n n n ect ep τ ω ( ) R n + ) ( ϑ

11 3. Chnge of Coodintes ct t t t n R R + ( ) n 4. Nomlize to R L to X cτ 11

12 1 5. Received wvefom with ( ) ( ) ( ) g dd h γ ( ) ( ) τ π γ γ c j ep ( ) [ ] w R L j R c X R c X P g ep ect τ τ L X π

13 III. SAR esponse in fequency-domin 1. SAR signl spectum H ( ) d d h( ) ep( j ) ep( j ) G ddγ ddγ whee ( ) d d g( ) ep( j ) ep( j ) ( ) ep( j) ep( j) G( ) ( ) d d g( ) ep[ j( ) ] ep[ j( ) ] is the SAR tnsfe function. Simplest cse H ( ) ddγ( ) ep( j) ep( j) G( ) Γ( ) G( ) 13

14 Pocessing Asymptotic evlution of integls Tnsfe Function epnsion Now Focus SAR Wide Focus SAR 14

15 I. Asymptotic evlution of integls 1. Type of integl I ( Ω) dtf ( t) ep[ jωq( t) ] with Ω >> 1. Asymptotic evlution q I () t q( t ) s ( ts ) ( ) t t q ( t ) ( Ω) ~ dtf ( t) ep[ jωq( t )] q +! s s s ep jωq s ( t t ) s ~ πj Ωq s f ( t ) ep[ jωq( t )] s s 15

16 3. Emples F ( ) 1/ dq ep[ jq] ep[ jq ] ~ ect ep j 1/ 16

17 17 II. Tnsfe function evlution ( ) f f f X c p X c R f R L p R c X R L p p R c X q p ω π ε τ + τ π τ ε + + τ + + Ψ τ Convenient evlution fom Let we hve ( ) ( ) [ ] [ ] [ ] ( ) [ ] Ψ q q P q j dq p w p j dp G ect ep ep 1

18 Fo chiped signl G with Ψ ( ) dp ep[ jψ ( p) ] w [ p ] dq ep[ j ( q) ] ect[ q] ( q) 1 Ψ q q L ( p) p R Ψ ε π fτ 18

19 19. Asymptotic evlution ( ) ( ) ( ) [ ] ( ) [ ] j w j w G ep ect ep ect ~ π π Ψ Ψ with ( ) + ε + + ε Ψ w L L L ect 1 1 4

20 3. Simplest SAR tnsfe function epession Epnsion ound leds to + ε + ε + ε L L L 1 4 / 1 1 nd with Accodingly ( ) + ε + ε Ψ ( ) j j G 4 ep ect 4 ep ect

21 1 4. Resolution f f f L X L d d G H j j d d G H G H / / 1 / )] ' ( )]sinc[ ' ( )sinc[ ( ) *( ) ( '] ']ep[ ep[ 1 ect ) ect ( ) *( ) ( ) ( ) ( ) ( Γ Γ τ π π γ π

22 III. Tnsfe function epnsion 1. SAR tnsfe function eclled ( ) ( ) ( ) [ ] ( ) [ ] ( ) ep ect ep ect ~ + ε + + ε Ψ Ψ π Ψ π L L L j w j w G

23 3. Tnsfe function phse epnsion ound Let ( ) ( ) ) ( ) ( + Ψ Ψ K with ( ) ( ) ( ) ε + + ε + ε + + ε Ψ Ψ L L L K L L L

24 we hve K with µ v ζ ( ) µ ( ) + v( ) + ζ( ) ( ) ( ) ( ) ε ε 4

25 III. Now focus SAR 1. Simplest ppoimtion Assume µ v ζ G ( ) G ( ). SAR pocessing Fom H ( ) G( ) Γ( ) we get * ( ) H ( ) ( ) Γ G 5

26 3. Emples Refeence Imge 6

27 Uncompensted µ ( ) tem 7

28 Uncompensted v( ) tem 8

29 IV. Wide focus SAR 1. Stting point H G ( ) G ( ) ddγ( ) ep( j) ep[ j( + K( ) ) ] ( ) Γ[ + K( ) ] with K ( ) µ ( ) + v( ) Accodingly H ( ) G( ) Γ[ ( 1+ v( ) ) + µ ( ) ] G( ) Γ[ Ω( ) + µ ( ) ] Ω( ) 1+ v( ) 9

30 . Rnge pocessing FT 1 ep * 1 [ H ( ) G ( ) ] dep[ j ] Γ[ Ω( ) + µ ( ) ] jµ ( ) Ω ˆ π ( ) γ Ω( ) 3

31 3. Simplest cse v so tht Ω 1 H ( ) G ( ) Γ[ + µ ( ) ] 31

32 4. Chip scling Ω B C D A B D ( 1+ B D) ( 1+ B D) 3

33 Rnge pocessing 33

34 Full pocessing 34

35 Intefeometic SAR Bsic pinciples Decoeltion effects Phse Unwpping techniques Emples 35

36 I. Bsic pinciples 1. Geomety Single imging senso Dul imging senso 36

37 Reltions ( + δ ) + l l sin( ϑ β) z led to H cosϑ z z ϑ + δ sin ϑ δ ϑ δ l cos. Intefeometic phse 4π [ ] δ * ( ) Ph γˆ ( ) γˆ ( + δ ) ϕ 1 so tht z sin ϑ l cos ( ϑ β) sin ϑ z ϕ 4πl ϕ 4π sin ϑ ( ϑ β) l cos( ϑ β) sin ϑ ϕ 4πl 37

38 In ode to compute the intefeometic phse the following steps must e implemented () A couple of SLC imges must e geneted 38

39 39 () The two imges must e egisteed fo infinite ndwidth SAR ( ) ( ) ( ) [ ] ( ) [ ] ( ) ( ) ( ) ( ) [ ] ( ) [ ] j dd j dd δ + δ π γ γ π γ γ sinc sinc 4 ep ˆ sinc sinc 4 ep ˆ 1 ( ) ( ) ( ) ( ) π δ γ γ π γ γ j j 4 ep ˆ 4 ep ˆ 1 nd egisttion is equied ( ) ( ) ( ) ( ) + δ π γ + δ γ γ j 4 ep ˆ ˆ

40 Intefeometic finges 4

41 II Decoeltion effects 1. Misegisttion ccucy of 1/ of piel is equied. Sptil decoeltion The sme cell is imged fom two diffeent looking diections l c cotnϑ l l c 41

42 3. Dopple centoid decoeltion The sme cell is imged fom two diffeent squint ngles 4

43 4. Tempol decoeltion Pesent only in dul pss systems 5. Ovell decoeltion estimte Coss-coeltion fcto χ * E[ ~ γ ~ 1γ ] p k ep ~ ~ E[ γ ] E[ γ ] q q 1 1 ( jϕ ) coheency mp 43

44 III. Topogphic mpping 1. Idel Phse Unwpping (PhU)pocedue ϕ m π s π π π ϕ m ϕ π π π π π π 44

45 . Discontinuities pesence () Non-miguous phse jump () Amiguous phse jump 45

46 IV. Phse unwpping techniques 1. Locl pocedue. Glol pocedues: Lest men sque method L [ ϕ] ds[ ( ϕ s) ( ϕ s) ] min S 46

47 3. Glol pocedue: Geen s identity method S ds [ ϕ g + ϕ g] c g dcϕ n ϕ g ( ) δ ( ) ( ) ds g( ) ϕ( ) + dc ϕ( ) S S c g ( ) n 47

48 48 4. Locl nd glol PhU techniques ( ) ( ) ( ) ( ) ( ) ( ) + + s n n s ˆ 1 ˆ ˆ ˆ ˆ ˆ M M M M M M d d d d d θ θ ϕ θ π ϕ π θ ϕ θ θ π θ ϕ π π π

49 V. Emples: Sdini Itly DEM Intefeometic SAR Dt Amplitude Phse Coheence Rw dt ESA copyight 49

50 This shot couse is ove: I do hope ll of you enjoyed it. 5