xu 1981 extraction of geol lineaments

8/8/2019 Xu 1981 Extraction of Geol Lineaments

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LARS Symposia Laboratory for Applications of Remote Sensing

1-1-1981

Extraction of Geological Lineaments fromLANDSAT Imagery by Using Local Variance and

Gradient TrendS. R. XuC. C. Li

N. K. Flint

This document has been made available through Purdue e-Pubs, a service of the Purdue University Libraries. Please contact [email protected] for

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Xu, S. R.; Li, C. C.; and Flint, N. K., "Extraction of Geological Lineaments from LANDSAT Imagery by Using Local Variance andGradient Trend" (1981).LARS Symposia. Paper 415.http://docs.lib.purdue.edu/lars_symp/415
http://docs.lib.purdue.edu/http://docs.lib.purdue.edu/lars_symphttp://docs.lib.purdue.edu/larshttp://docs.lib.purdue.edu/larshttp://docs.lib.purdue.edu/lars_symphttp://docs.lib.purdue.edu/


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Reprinted from

Seventh International Symposium

Machine Processing of

Remotely Sensed Data

with special emphasis on

Range, Forest and Wetlands Assessment

June 23 - 26, 1981

Proceedings

Purdue University

The Laboratory for Applications of Remote Sensing

West Lafayette, Indiana 47907 USA

Copyright 1981

by Purdue Research Foundation, West Lafayette, Indiana 47907. All Rights Reserved.

This paper is provided for personal educational use only,

under permission from Purdue Research Foundation.

Purdue Research Foundation


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EXTRACTION OF GEOLOGICAL LINEAMENTSFROM LANDSAT U1AGERY BY USING LOCALVARIANCE AND GRADIENT TRENDS,R, xU J C,C, LIJ N,K, FLINTuniver s i ty o f P i t t sburghp i t t s bu r gh , Pennsylvania

ABSTRACTA method fo r computer e x t r a c t i o n of

geo log ica l l i neamen t s from LANDSAT imagesi s pr e s en t ed . The va r i ance t h r e sho ldedmap of each image i s sepa ra t ed in to e i g h tg r ad i en t d i r e c t i on maps, where bas i cl i ne a r segments a re de te rmined each ofwhich i s based on th e p r i n c i p a l e igenvec to r of a c l u s t e r o f p i x e l s whosegr ad i en t d i r e c t i on i s or thogona l to itso r i e n t a t i o n . A spe c ia l l i nk i ng a lgo r i t hmopera t e s on th e bas i c l i n e a r segments togive a cand ida t e l ineament segment . Th emethod has been exper imented on LANDSATimages of a sma l l r eg ion southwes t toP i t t s b u r g h . The pr e l i m i na r y r e s u l t i sencourag ing and f u r t h e r work fo r improvement i s sugges t ed .

I . INTRODUCTIONI n t e r p r e t a t i on of l i neamen t s from

LANDSAT images has s i g n i f i c a n t a p p l i c a t i ons to geo l og i ca l s t u d i e s . They ma yr e f le c t s t r u c t u r a l f e a tu re s as s u r f acem an i f e s t a t i on of pos s i b l e f r a c t u r e s an df a u l t s , and may be used to a id i n t heplacement o f geo l og i ca l measurements fo rexp lo ra t i on of pe t ro l eum/gas and minera lr e sou rces . 1 - 4 Lineaments a re us ua l l ys i t ua t ed i n a h igh ly t ex t u r ed image background. Some l i neamen t s appea r r a t h e rprominent whi l e o t he r s s u b t l e ; t h e i rv i s ua l i n t e r p r e t a t i on i s of t en qu i t esUb jec t ive . 5 Linea r enhancement andcomputer-a ided e x t ra c t ion of l i neamen t shave been s tud i ed by Podwysocki , e t a l . 6an d Chavez, e t a l . 7 A t e chn ique fo rd i g i t a l enhancement by combiningpr i nc i pa l component a n a l y s i s with m u l t i s pec t r a l c l a s s i f i c a t i o n wa s deve loped byFon t a ne l , e t a l . 8 and app l i ed byH i l a l i , e t a l . 9 Th e performanc e ofa lgor i thms of l i n e a r , s em i l i nea r , and

non l i nea r d e t e c t o r s was examined . and analgor i thm f e r i t e ra t i . ve pnhancement ofl i ne a r f e a tu re s was deve loped byVanderbrug. 10 Match filters were usedby Ehr ich in pr ep r oces s i ng f o r au toma t i ce x t ra c t ion of l i neamen t segments whichwere then l i nked by means of dynamicprogramming. ll Recen t ly , J ackson , e t a l .conduc ted an ex t ens i ve s tudy by va r i ousmethods on ~ o m p u t e r enhancement of i n t e r pr e t a t i ve l i neamen t s in the remote lysensed images of C o t t a g e v i l l e , WestV i r g i n i a , and deve loped a method ofgr ad i en t f i l t e r i n g fo r enhancement ofd i r e c t i o n a l t r e nds . 12 ,13 A ll o f t he s es tud ie s have been d i r e c t e d towardsproviding an improved c a pa b i l i t y ofcompute r -a ided i n t e r p r e t a t i o n ofgeo l og i ca l l i neam en t s . This pape ri n t ends to pr e s en t our pr og r e s s in t h i sa re a .

Lineaments a re l i n e - l i k e f e a t u r e sin a t e r r a i n . Along a l i neamen t , t het r ans ve r s e changes in gray v a l u e p e r s i s t ,but its edge c h a r a c t e r i s t i c s may v a r y .Hence, it must be pe rce ived bo t h l oc a l l yand g loba l ly . Three c h a r a c t e r i s t i c s ofa l i neamen t a re no ted : (1) wi t h i n itssma l l ne ighborhood, one s i de shows da rke rshade whi l e th e o t h e r s ide i s br i gh t e r ;(2) the var iance of graynes s in it s s ma l lneighborhood i s of t en l a rge to accountfor the change i n g r aynes s ac r os s th el ineament ; and (3) th e p i x e l s a long al i ne a me n t most ly have more or l e s s th esame g r a d i e n t d i r e c t i o n , a l though t h e i rd i r e c t i o n s ma y be r eve r sed a t somep l a c e s , an d t h e i r t r end mus t con t inuefo r a s i g n i f i c a n t l e ng th . These f e a tu re sa re i nco rpo ra t ed in our l i neamen t modelfor a lgor i thm deve lopment .

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I I . DETECTION OF BASIC LINEAR SEGMENTSEach of th e m ul t i s pe c t r a l imagesunder c ons ide ra t ion i s prep roces sed firstby l e ve l s l i c i ng to s t r e t c h its gray

range to 2S 6 l e v e l s . Cons ide r a sma l lnx n window ( fo r example, n = 3) cen te r edaround each p i x e l (i,j), and compute itsmean gray l e ve l "Eij and its va r i ance 0 i jwi t h i n the window. These l oc a lstatistics may be used fo r c o n t r a s tenhancement an d no i s e f i l t e r i n g . 14 Bychoos ing an a pp rop r i a t e t h r e s ho l d value0 t of th e l o c a l va r i a nc e , a r eg ion ofhigh nonhomogeneity i s segmented byl oc a t ing t hose p i x e l s whose l oc a l v a r i ance 0 i j i s g r e a t e r than 0 t . Within sucha va r i ance t h r e s ho l ded map, the narrowreg ion around a l i neamen t segment i sexpec ted to lie. The l o c a l va r i anceparameter has a l s o been used in proce s s i ng SEASAT SAR images fo r c l a s s i f y i n gs t a t i s t i c a l l y homogeneous subregions int he po l a r i c e r e g ion . lS From the pool ofp i x e l s in the va r i ance thresholded map,t h e i r gra d ie n t d i r e c t i o n s a re examinedfo r p o s s i b l e t r ends of l i neamen t s e g m e n t ~

For t hose p i x e l s which e x i s t in th eva r i ance thresholded map, t h e i r Sobelgra d ie n t s a re eva l ua t ed . Each of t he s ep i x e l s , (i,j), and its 3x3 ne ighbor s inth e image a re convolved by ope r a t o r s HIand H2 to g ive the hor i z on ta l and v e r t i c a l d i f f e r e n c e s Sl(i,j) and S 2 ( i , j )r e s pe c t i ve l y . Both th e magni tude an dd i r e c t i on of th e Sobe l gra d ie n t S ( i , j )a re computed . The gra d ie n t d i r e c t i on i squan t i zed i n to e igh t d i r e c t i on numbers( 0 , 1 , 2 , .. , 7 ) , with d i r e c t i onpo i n t i ng to the e a s t and 1 d i r e c t i onpOint ing to th e n o r t h e a s t , e t c . Eachp ixe l i n th e va r i ance t h r e s ho l ded mapmay then be l abe l ed by its d i r e c t i oncode . Eigh t gra d ie n t d i r e c t i on maps a rethen s epa r a t ed , each of which r e p re se n t st hose p i x e l s whose gr ad i en t d i r e c t i onsa re a l ~ coded by the same number q,(q = 0 , 1 , 2 , .... , 7 ) . Search i s thenat tempted in e.ach d i r e c t i on map to ob t a i np i x e l s fo rming poss ib l e l i n e a r segmentswith a d i r e c t i on or t hogona l to thegr ad i en t d i r e c t i on of th e map.

Cons ide r a square wind.ow of mxmp i xe l s (m = 32 in t h i s s tudy) in a d i r e c t i on map with d i r e c t i on q. Examine thenumber and d i s t r i b u t i o n of p i x e l s in th ewindow, and eva l ua t e e igen va l ues (A Iand A2) and e igen ve c to r s ( ~ l an d ~ 2 ) oft h i s c l u s t e r of p i x e l s . I f t he re e x i s t sa s i n g l e c l u s t e r of con t iguous p ixe l swhich a re a l igned l i n e a r l y with a d i r e c -

t ion or thogona l to the gr ad i en t d i r e c t i on q, t he s e p ixe l s na t u r a l l y form asegment of a poss ib l e l i neamen t . I f ac l u s t e r of su f f i c i e n t number of p i xe l s ,not ne c e ssa r i ly con t iguous , i s s i g n i f i can t l y e l onga t ed , the p r i n c i p a l e igenvec t o r pass ing through th e c l u s t e rcen t e r may be an adequa te r e p re se n ta t ionof a l i ne a r segment. Let N be the numberof p ixe l s i n the c l u s t e r in a window, andr = Al/A2 be th e r a t i o of e igen va l ues ofth e c l u s t e r . I f N a n d r are gre a te r thent h e i r r e spe c t ive th reshold va lues Nt andr t , an d fu r the rmore , i f the d i r e c t i on ofits p r i n c i p a l eigen vec t o r i s or thogona lto the gra d ie n t d i r e c t i on with in 22.Sot o l e ra nc e , t h i s e igen vec t o r extendingbetween tw o s i de s of th e squa re window,as shown in Figure 1 , i s accepted as abas ic l i ne a r segment whose or i e n t a t i oni s now no t r e s t r i c t e d to a quant izedd i r e c t i on . Th e use of th e c l u s t e r eigenvec t o r pe rmi t s us to de te c t a poss ib l el ineament segment even when it i si n t e r rup te d i n t he middle as long as thegra d ie n t d i r e c t i ons of th e p ixe l s a rec o n s i s t e n t so as to prov ide a l ineamentt r end .

This proces s i s repea ted in a l ls ucces s i ve windows in a given d i r e c t i onmap and fo r a l l d i r e c t i ons to d e t e c t allbaSic l i ne a r segments in an image. Itshould be noted t ha t any tw o s ucces s i vewindows a re over lapped SO% e i t he rhor i z on ta l ly or v e r t i c a l l y i n o rde r t ot ake care of th e cases where a c l u s t e rmay be s p l i t by a window in to tw o smal lp a r t s below th e th reshold s i z e .I I I . LINKING OF BASIC LINEAR SEGMENTS

The pr oces s of l i nk ing bas i c l i ne a rsegments should be viewed as a meansof approx ima t ion . It i s no t of t en tof ind tw o bas ic l i ne a r segments which a repre c i se ly a l igned or which can be c onnected from en d to end. Thus , th el i nk ing of two n ~ i g h b o r i n g segments i sachieved by connect ing t he i r r e s p e c t i v ec l u s t e r c e n te r s to prov ide a p iecewisel i n e a r approx ima t ion .

For a bas ic l i ne a r segment Lkin "window k", s ea rch i s made to l i nkit with ano the r bas ic l i ne a r segment,i f e x i s t s , in one of its t h r ee ne ighbor ing windows. Depending upon whether theor i e n t a t i on of Lk i s c lo se r to the v e r t i c a l , h o r i z o n t a l , or d iagona l d i r e c t i o n ,t he t h r ee neighbor ing windpws a re spec-\.f i ed by "window k+ l " , "window k+2" an d"window k+3" as shown in Figure 2 ( a ) ,

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(b) an d ( c ) ; an d they are searched int ha t orde r . I f a bas ic l i ne a r segmentLk+l e x i s t s in "window k+l" and i f th ed i f f e r e n c e in or i e n t a t i on between Lk andLk+l i s l e s s than 4S o , they a re a l lowedto be l i nked t oge t he r by connec t ing t h e i rr e spe c t ive c l u s t e r c e n te r s Ck and Ck+l asi l l u s t r a t e d in Figure 3. Otherwise , t h e i rd i r e c t i ons a re i nc ons i s t e n t , so Lk+ lshould no t be l inked to Lk. I f t he re i sno bas ic l i ne a r segment, in "windows k+l ,k+ 2 an d k+3", which can be connec ted toLk , the nex t s e t of t h re e windows shouldbe searched as i nd i ca t ed by "window k+4","window. k+S" and "window k+6" in Figure2 (d ) , (e ) an d ( 0 . I f the search i ssuc c e ss fu l , th e c u r re n t l i nk i ng proces scan be cont inued forward; o t he r wi s e ,the process s tops a t Lk and a ne w l i nk inge f f o r t w i l l s t a r t a t ano the r window. Asshown in Figure 3, the suc c e ss fu l l i nk ingof a s e r i e s of bas i c l i ne a r segments prov ides an extended p iecewise l i n e a rs t r uc t u r e fo l lowing a t r end which i s o r t h ogonal to the ave rage gra d ie n t d i r e c t i onof the p ixe l s on the l i n e . In t h i s way,candida te l i neamen t s a re e x t ra c t e d fromthose p ixe l s having the s imi l a r g ra d ie n td i r e c t i on an d being no t too f a r separa tedeven though no t con t iguous .

IV. EXPERIMENTAL RESULTSA por t ion of LANDSAT-l image of a reg ionsouthwest to Pi t t sbu rgh has been e xpe r i mented by the above -desc r ibed method.Th e images from four s pe c t r a l bands

are shown in Figure 4 ( a ) , ( b ) , (c ) an d(d ) . Each image i s of S12 x 1024 s i z e .A l ineament map in t h i s r eg i on a s viewedby two ge o log i s t s i s shown in Figure S.A t o t a l of 20 l i neamen t s were mapped.

Only one ha l f on each image c ons i s t ingof 51 2 x S12 p ixe l s was processed a t at ime; the r e su l t s were then combined.Th e va r i ance t h r e s ho l d a t fo r each imagewas chosen as t ha t va lue of a such t ha tthe upper 10% under the va r i ance h i s t o gram was covered fo r a > a t . In the d e t e c t ion of bas ic l i ne a r segment s , twose t s of th reshold parameters Nt and rtwere used. I f N > Nt = 32, then r > r t = l . S .I f 322. N>16, then r>r t=8 . Th e l eng t h ofthe bas ic l i ne a r segments va r i ed between16 p ixe l s to 32 p i xe l s , corresponding tothe a c t u a l l eng t h of approximate ly 1 to2 km. .

The proces s ing r e s u l t s ob ta ined fo rthe images of a l l 4 s pe c t r a l bands a reshown in Figure 6 ( a ) , (b ) , (c) and (d) .Combining these r e s u l t s , 13 segments ofl ineaments were e x t ra c t e d by t h i s method.

Many spu r ious sho r t l i n e a r segmentswere found, which were no t t r ue l i n e a ment segment s .V. DISCUSSIONS

It i s appa ren t t h a t th e e xpe r i menta l r e s u l t gave a cons i de r ab l eamount of e r r o r in the automat ic de t e c t i on of l ineaments . A c lo se examinat ion sugges ted s e v e r a l problemsfo r fu r the r c ons ide ra t ion . Longl ineaments were no t f u l l y t r a c t e d bycomputer process ing because the t h r e s h holded var iance maps f a i l e d t o p rov ides u f f i c i e n t reg ions for e x t r a c t i on ofbas i c l i n e a r segments . A more r e f ine dprep roces s ing should be performed ino rde r to improve the de te c t ion a c c u r a c ~ A l a rge r window ( f o r example, 64x64p ixe l s ) and separa te c l u s t e r seekingmay be pre fe r re d fo r more r e l i a b l ei d e n t i f i c a t i o n of bas i c l i n e a r s e g m e n t ~ A more global t rend search should bef u r t h e r developed to i de n t i f y theposs ib l e a l ignment of se ve ra l l i n e a rsegments which a re separa ted f a r a p a r t . Some of the spur ious sho r t segments may then be discarded as they in d iv idua l ly do no t fi t in to a longert rend . These a spe c t s a re being pre se n t ly inve s t iga t e d fo r f u r t he r im provement .

1 .VI. REFERENCES

Smith, W.L., e d . , "Remote-SensingAppl ica t ions for Minera l Explor a t i o n , " Dowden, Hutchinson and Ross,I n c . , St roudsburg , P a . , 1977.

2. Sab ins , F . F . , J r . ,"Remote Sens ings :Pr inc ip les and I n t e r p r e t a t i o n , "W.H. Freeman and Co. , San Fr anc i s o ,Ca. , 1978.

3. Werner , E ., "App l i ca t i on of RemoteSensing St ud i e s to the I n t e r p r e t a t i on of Fr ac t u r e Systems an dS t r uc t u r a l Sty le s in the Pla teauRegions of Eas tern Kentucky, Southwes tern Vi r g i n i a and SouthwesternWest Virgin ia fo r App l i ca t i on toFoss i l Fuel Ext ra c t ion P roc e sse s , "Fina l Repor t , UGR F i l e No . 040,DOE Morgantown Energy TechnologyCenter , December 1977.

4. Goetz, A.F.H. an d L.C. Rowan."Geologic Remote Sens i ng , " Sc i ence ,Vol. 211, pp. 781-791, 20 Februa ry1981.

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5. S i e g a l , B.S. an d N.M.Short , " s i g n i f i c a n c e of Opera tor Var ia t i o nand th e Angle o f I l lumina t ion in L i n e ~ ment Analys is on Synopt ic Images , "Modern Geology, Vol. 6, pp.75-85 ,1977.6. Podwysocki , M.H., J .G . Moik an d W.C.Shoup, "Quant i f i ca t ion of Geologic .Lineaments by Manual and Machine Pro

cess ing Techniques ," Proc . NASAEar th Resources Survey Symposium,Houston , Tx , Vol . I -B , pp. 885-903,June 1975.

7. Chavez, P .S . , Jr., G.L. Ber l in andA.V. Acosta , "Computer Process ingof LANDSAT MSS D i g i s t a l Data fo rLinear Enhancements ," Proc . 2nd

8 .

Annual W.T. Pecora Memorial Symposium,Mapping with Remote Sensing Data,Sioux Fa l l s , S.D. , pp. 235-250,October 1976.Fo n tan e l , A ., C. Blanchet and C.Lal lemand, "Enhancement o f LANDSATImaginery by Combinat ion of Mu l t i sp e c t r a l C l a s s i f i c a t i o n an d Pr i n c i p a l Component An aly s i s , " Pr-oc. NASAEar th Resourcws Survey Symposium,Houston , Tx, Vol. I -B , pp. 991-1012June 1975.

9. H i l a l i , E . , A. Demnat i , J .C. Rivereauand B. Soulho l , "Cont r ibu t ion De sImages LANDSAT A La Prospect ionGeologique Dans L ~ s Regions De LaMedite rranee Occid en ta l e , " Pr oc .I n t e r n a t i o n a l Conference on EarthObserva t ions from Space and Management o f Plan e t a ry Resources , Toulouse,France , European Space Agency SP-134,pp. 133-140 , May 1978.

10. Vanderbrug, G . J . , "Line Detec t ion inS a t e l l i t e Imagery ," IEEE Trans . onGeosc ience E l e c t r o n i c s , Vol. GE-14,N o . 1 , pp. 37-44 , January 1976.11. En r ic h , R.W., "Detect ion of GlobalEdges in Textured Images ," IEEE

Trans . on Computers, Vol. C-26,N o . 6 , pp. 589-603, June 1977.12. Jackson , P . L . , H.L. Wagner and R.A.Schuchman, "Geolog ic Remote SensingOver The C o t t a g e v i l l e , West Virg in i a ,

Ga s Fi e l d , " Fin a l Repor t No . 130700-13-F , Envi ronmenta l Research I n s t i t u t e o f Michigan , Ann Arbor, Mich.February 1979.

13 . Wagner, W.L . . an d P . L ~ , Jackson ,"Fe a tu re Enhancement Using D i g i t a lShaded Rel i e f Process ing Techniques ,"Proc . 13th I n t e r n a t i o n a l Symposiumon Remote Sensing of the Environment ,Ann Arbor, Mich. , pp. 1721-1725,1979.

14. Lee, J . S . , "Dig i ta l Image Process ingby Us e of Local St a t i s t i C S , " Pr oc .IEEE Conference on Pat t e rn Recogni t ion and Image Pro c e s s in g , Chicago,IL , pp. 55-61, 1978.

15. Tang, G.Y. , "Class i f i ca t ion ofSEASAT-1 SAR Images of Polar IceRegions ," presen ted a t the IEEEWorkshop on D i g i t a l Signa l an dWaveform An a ly s i s , Miami Beach,FL, December 5, 1980.

ACKNOWLEDGEMENTTh e p a t t e r n r eco g n i t i o n an d imagep ro c e s s in g r esea rch f ac i l i t y used wa s

supported in par t by the Natura l Sc ience~ o u n d a t i o n gran t s ENG 79-11371 an d~ C S 77-09374.

A c lu s t e r of p i x e l s whose g rad ien td i r e c t i o n i s q

n x 3 2windowc l u s t e r cen te r

P r i n c i p a l e igen vector witho r i e n t a t i o n orthogona l toth e grad ien t d i r e c t i o n q

Pigure 1 - Basic l i n e a r segment d e t e r mined by th e p r i n c i p a l eigen v ec to r ofa c l u s t e r of p i x e l s in a grad ien td i r e c t i o n map.

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Window k

r - - - ~ 1 ; - - - - 1 - - - - - " I, ,

I I: ,I I' ,I ' ,: \ j :LL J = = k 1 - - - - - - - ~ I Window k+l \

Window k+2 Window k+3(a )

W~ I l ( h ) ! l _ Fj-_j", . , ,

( b)r - - ..... -----.,, , Window

Window kJ Window k : ......L!+6'\ ,J t ,,,1ipIhr - - -r=-- 'r----- - - - - - ~

I ! I: :I :: I 'f I I: .Li _L .L_\J __ '.l

\ . Window k+4 \

,I 1____Window k+5

Window k+5 Window k+6(d ) ( e)

r- -------- -:Window k+3- -- , 'II "

I : - - - - - ~ 1 ' ,--;--"'"'{ _ l - _ - _ ~ - . J Window

Window k+2k+l

(c )

Window k+6i----\----:, I, ,I ,L . . . . - - r , . . . . . , ~ , . . . , . j : . . , ; -,:

1 " I ": IL - - - -1 - - -L, I ,I \L I J WindowL _ _ .... k+ 4Window k+ 5

( f )Figure 2 - Neighbouring windows of "window k" spe c i f i e d i n s ea r ch fo r connect ionof bas ic l i n e a r segments ,

'I ," C: : k+l: ,- ----" '"::: Ck+2r - _ . . ! b ~ . ' - _.-

Figure 3 - Linking a se r i e s of bas ic l i ne a r segments

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(3 ) Band 4

(b ) Band 5Figure 4 - LANDSAT - l images of a region southwest to Pi t t sburgh , PA.

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(c ) Band 6

(d ) Band 7Bigure 4 - (Cont inued)

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'r'III

1, 120

Figure 5 _ A l i ne amen t map de te rmined by two geo l og i s t s fo r a r eg iondef ined in Figure 4 .

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(a ) Band 4

(b ) Band 5Figu r e 6 - Lineaments ex t r a c t ed by computer process i ng .

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(e ) Band 6

(d ) Band 7Figu r e 6 - (Cont inued)

1981 h1achine Processing of RemollZly Sensed Data Symposium

xu 1981 extraction of geol lineaments

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