SPECTRAL UNMIXING FOR INFORMATION EXTRACTION. R.Kancheva, D.Borisova*

Transcription

1 SPECTRAL UNMIXING FOR INFORMATION EXTRACTION R.Kanchea, D.Borioa* STIL-BAS Aca.G.Bonche tr., bl.3, 3 Sofia, Bulgaria rumik@ab.bg / borioa@til.ba.bg KEY WORDS: Remote Sening, Agriculture Crop, Data Analyi, Theory Application, Lan Coer Claification ABSTRACT: From piel to procee thi the hortet an mot eential formulation of all tuie, eperiment an inetigation carrie out in the fiel of Earth remote ening oberation. Thi formulation reeal two main irection of ata interpretation: the firt relate to claification an feature retrieal, an the econ aociate with multi-temporal apect of remotely ene ata an concerning change etection an procee tracking an moeling. State aement, tren forecating an preiction are the goal of the enironmental an lan coer monitoring. Further implementation of the inetigation reult reemble the eciion making an problem-oling nature of remotely ene ata output. The eelopment of efficient technologie for ata analyi i one of the mot challenging iue that the remote ening community i facing. Matter of ata reuction, proceing algorithm accuracy, information amount, cot an time aing etermine the efficiency of ata analyi. The importance of thi iue i irectly connecte with the eer-increaing quantity of ata proie by numerou optical, thermal an microwae enor, with their ynergitic ue a well a with the accuracy of ata proceing algorithm an reult erification. With all thi in min we preent here ome reult from a tuy of ifferent pectral unmiing technique oer rock-oil-egetation object in relation to miture ecompoition, object type an proportion etermination an biophyical propertie retrieal. Eperimental ata from fiel an laboratory pectral reflectance meaurement in the iible an near infrare ban hae been ue, ariou ecompoition metho (linear unmiing, clutering, colorimetric analye, etc.) hae been applie an ealuate, comparion between empirical an imulation moel ha been performe.. INTRODUCTION The eelopment of efficient technologie for ata analyi i one of the mot challenging iue that the remote ening community i facing. Matter of ata reuction, proceing algorithm accuracy, information amount, cot an time aing etermine the efficiency of ata analyi. The importance of thi iue i irectly connecte with the eer-increaing quantity of ata proie by numerou airborne, fiel an laboratory operate enor, with their ynergitic ue a well a with the accuracy of ata proceing algorithm an reult erification. With all thi in min we preent here ome reult from a tuy of ifferent pectral unmiing technique oer rock-oilegetation object in relation to miture ecompoition, object type an proportion etermination an biophyical propertie retrieal. Eperimental ata from fiel an laboratory pectral reflectance meaurement in the iible an near infrare ban hae been ue, ariou ecompoition metho (linear unmiing, colorimetric analye, clutering, etc.) hae been applie an ealuate, comparion between empirical an imulation moel ha been performe. Spectral linear unmiing i efficient approach to the pectral ecompoition of multichannel remotely ene ata. A main problem to it proce i that the number of pectral component (en-member) ha to be correctly itinguihe. The applie metho are tuie for their potential to ecompoe miture component from pectral reflectance ata in two cae. In the firt cae on the eample of oil-egetation coer the influence of the ifferent oil backgroun an plant enecence (change in chlorophyll content uring the growing perio) on egetation reflectance an color feature are analyze. Spectral tranformation technique an colorimetrical analyi of eperimental an moele ata et are ue. Some reult of thi tuy concerning the etimation of green egetation fraction coer are hown. In the econ cae on the eample of rock-oil-egetation lan coer the relationhip between pectral reflectance of mie piel an fraction coer of rock, oil an egetation therein an the ealuation the poibility of uing pectral miture ecompoition in relation to their type an proportion etermination are ecribe. 2. MATERIALS AND METHODS Stuy cae one Groun-bae fiel an greenhoue reflectance meaurement of wheat, barley, alfalfa, gralan with ifferent oil backgroun an egree of enecence are carrie out with multichannel raiometer (Krumo, 983; Ilie, 00) in the VIS an NIR pectral ban. The oil ariety wa preente by ark an light oil (chernozem, brown, grey foret, alluial). The pectral reflectance cure of ome of them are preente in Fig.a illutrating the wie range of oil reflectance ignature. The reflectance pectra of meaow with ifferent egetation fraction coer are hown in Fig.b where the impact of the oil type: ark chernozem () an light alluial oil (2) i * Correponing author.

2 The International Archie of the Photogrammetry, Remote Sening an Spatial Information Science, obere. Some pectral tranformation well-known a egetation inice (Table ) ue in egetation tuie are calculate in the green (G 550 nm), re (R 670 nm) an near infrare (NIR 800 nm) ban. In the cae of oil an green egetation, for intance, coniering that pi i : N VI N VI (NIR-R)/(NIR+R) 3 (G-R)/(G+R) 2 NIR/R 4 G+NIR-2R r p r + ( p ) r (2) Table. Vegetation inice ( r r ) r r p + (3) reflectance, % 0 alluial grey chernozem The tritimulu alue X,Y,Z, chromaticity coefficient,y,z an ominant waelength λ of the meaure object an moele miture are compute in the pectral range nm accoring to the CIE 964 metho an D65 light ource. Accoring to the unmiing theory the following equation are worke out (the ame being true for Y, Z an WX+Y+Z) (Mihe, 992; Kanchea, 03): waelength, nm a) 2b b P0.8 X [ p ( r r ) + r ] Δλ D 65 (4) λ ) X X + p (5) reflectance, % 0 2a P a p ( W W ) + W (6) p waelength, nm b) The (,y ) coorinate (Eq. (6)) efine the poition of oilegetation miture on the color locu an epen on the fraction coer of the en-member p. For a three-component miture incluing plant rie foliage: Figure. Reflectance pectra of ifferent oil (a) an oilgreen egetation miture (b) The ariety of green an rie egetation fraction coer the latter relate to chlorophyll ecreae in plant wa achiee uring plant eelopment tage or moele from bare oil an egetation full-canopy reflectance uing the unmiing theory (Mihe, 99): p ) + p p ( W W ) + p ( W W ) + W p ) + p p ( W W ) + p ( W W ) + W (7) (8) r Σ where p r i i i r Σ are the reulting pectral reflectance ignature of the miture, r i - the reflectance of the component (enmember) compoing the miture, () Statitical ata proceing wa carrie out to inetigate ariance in egetation reflectance an color feature ue to ifferent oil backgroun an plant coer (green an rie fraction). Correlation an regreion analyi wa applie to the eperimental an moele ata et to reeal the relationhip between ) the egetation inice an green egetation coer p, an 2) the ominant waelength λ an green egetation coer p. pi - component relatie amount (fraction coer).

3 The International Archie of the Photogrammetry, Remote Sening an Spatial Information Science, Stuy cae two Region of interet (ROI) in the econ tuy area Aarel- Meet i electe bae on TM ataet. Aarel-Meet an open pit copper mine (Figure 2) i ituate on an area of thouan ecare, about 000 m aboe ea leel, 90 km outheat from the capital of Bulgaria, Sofia, in the Sahtinka Srena Gora Mountain. During fiel campaign 05 granite, brown oil an gra ample are collecte. Mineral an chemical reference analye of rock an oil ample are carrie out. Fiel an laboratory pectral meaurement are alo implemente. Pinkih meiumgraine granite ample conit of aerage 50% orthoclae, 35% quartz, 5% plagioclae, % biotite an % magnetite. The parent material of the brown any loam oil ample i granite. The oil ample ha moerate to coare primatic tructure, ery har an friable with neutral ph (6.5) % organic carbon, 2% clay, 25% ilt an 62% an. The gralan egetation type i preente by Green Rye gra. Variou combination of pectral tranformation (Yane, 994; Чимитдоржиев, 998) are eamine for their correlation with plant bioparameter. Many of them emontrate high R 2 alue from 0.86 to A the normalize ifference of the meaure pectral reflectance in the re an near infrare ban i traitionally an mot wiely ue, the preente below eample refer mainly to thi pectral ine. In Figure 3 the tatitical relationhip of NDVI (NIR-R)/(NIR+R) an barley canopy coer (fraction coer) are hown. The epenence are erie eparately for the grey () an chernozem (2) oil plot. Regreion analyi wa applie to reeal the relationhip between λ an p. Strong correlation wa foun between the green canopy coer (fraction coer) an the ominant waelength of oil-egetation miture. The fitte epenence p f(λ ) are econ egree polynomial with coefficient of etermination 0.94 an 0.9 (at p<0.05 probability leel) an tanar error of etimation 0.07 an 0.09 for the ark an light oil cae repectiely. An eplanation of the better preictie accuracy of the ark oil moel coul be the bigger ifference of λ alue between miture with ifferent p (Figure 4). 0.8 R R NDVI canopy coer Figure 2. Open pit mine Aarel Multi-temporal pectral ignature are acquire in ROI in ummer 05 to monitor inter-annual change at the urface. The fiel reflectance pectra are obtaine with a TOMS (Thematically Oriente Multichannel Spectrometer) eigne an contructe in Remote Sening Department at STIL-BAS in collaboration with AAMU-USA (Petko, 05). Laboratory meaurement are performe with SPS- pectrometric ytem (Ilie, 00) alo eigne an built in the Dept. Fie pectra a aerage of 0 internal pectra are acquire oer each target. After being acquire, the pectra are correcte for relatie reflectance with the pectrum of a barium ulphate urface ue a white reference, to obtain abolute reflectance meaurement. Pot-proceing of the fiel an laboratory reflectance ata inclue remoal of ba ata, aeraging of the fie pectra per target, an if neceary moothing of the reulting pectra. The moele miture of en-member (pure lan coer clae) in piel are compare with the obtaine ata. The rockoil baeline an the relate to TM ban pectral tranformation for biophyical propertie retrieal are applie to en-member an moele ata. 3. RESULTS AND DISCUSSION Stuy cae one Figure 3. Depenence of the NDVI on barley canopy coer oer grey () an chernozem (2) oil green canopy coer (P) ominant waelength, nm 580 Figure 4. Green coer fitting moel p f(λ ) for ark ( ) an light (- - -) oil-egetation miture If the combine moel i applie the green coer alue are oeretimate for light oil miture (aeragely % in the whole p range) wherea in the cae of ark oil the p alue are uneretimate (5%) Table 2. Jut the oppoite i the ituation with VI. Thi proie a poibility for a mutual checking of the p alue etimate by λ or VI. The accuracy of the colorimetric miture ecompoition increae with increaing egetation fraction coer. One reaon i the maller ifference between λ of miture with equal coer an ifferent oil component (Table 3).

4 The International Archie of the Photogrammetry, Remote Sening an Spatial Information Science, meaure etimate error etimate error coerage (light oil) % (ark oil) % (-) (-) (-) proportionally increae oil impact. An eience i preente on Figure 6 where the poition on the color locu of two an three component miture of oil (ark or light), green an rie egetation are preente. y ark oil light oil 566 nm Table 2. Relatie error of green coer etimation uing the integrate p f (λ ) moel nm p Δλ, nm Table 3. Difference between λ for light an ark oilegetation miture The moel tuie i not reeal ignificant ifference aociate with egetation type. An eience i the narrow fullegetation canopy cluter ( nm) on the color locu in Figure 5 i clearly een a well a the wier ban of bare oil location where ry an wet oil with mooth an rough urface ( nm) are inclue. Thi i another reaon for the wort accuracy of low egetation coer aement, epecially when uing not-ifferentiate moel. The wier λ range of the oil cluter within the color locu an the narrower one of ariou full-coer green canopie uppoe bigger error in aement of pare egetation coer if the oil type an tate propertie are not taken into account. y nm 575 nm rie egetation green egetation Figure 6. Dominant waelength of 2- an 3-component miture Stuy cae two In 2-D pace of waelength (Figure 7) three type lan coer an their 2- an 3-component miture are preente. R-NIR pace i choen concerning well-known rock-oil baeline (Elige, 985) which i forme in relation to TM ban. For further comparion correponing pectral range of SPS- are ue. The alue of mi between two en-member fall on line connecting repectie lan coer type. Applying the regreion analyi we obtain the well-efine line for rock, oil an rockoil miture in R-NIR pace. The coorinate of egetation are ignificant ifferent becaue of pecific chlorophyll aborption in re ban an high reflectie in NIR ban. The coorinate of 3-compomemt mi fall in triangle oil-rock-egetation D65 oil rie eg. green eg NIR reflectance, % a a 2b +2b Figure 5. Dominant waelength of ariou oil type an fullcoer egetation canopie A an aitional eample ery light aline oil (λ 57 nm) an laterite re oil (λ 583 nm) in Figure 5 are left outie the cluter of the mot common an wiely prea oil type. One important thing to point out here i that rie egetation canopie an their oil miture lie within the oil ban an hae an aerage ominant waelength of 577 nm which i the ame a the aerage λ of the oil cluter. The enecence effect on egetation reflectance are quite imilar to the oil impact. Thi mean that the enecence influence on plant pectral an color feature can be conier equal to a 0 2a 0 40 RED reflectance, % Figure 7. NIR. RED reflectance (SPS- ata) of granite (), brown oil (2a) re oil (2b), gra (3) an 2- an 3- component miture (+) A another reult the poibility to obtain information about iron itribution in ROI from pectral ata i analyze. The ore mineral in Aarel-Meet opencat mine contain the iron an thi chemical element i a potential pollutant in the region. The iron aborption at 0.8 um i reuce in epth accoring to it

5 The International Archie of the Photogrammetry, Remote Sening an Spatial Information Science, content. The 0.9-um-aborption line hift poition with element ubtitute for iron (Clark, 999). pectral tranformation (.0 μm μm) / 0.9 μm iron content, % Figure 8. Depenence of the pectral tranformation (.0 um um)/0.9 um оn iron content in granite ( ), antone ( ), an brown oil ( ) On Figure 8 the epenence of the pectral tranformation (.0 um um)/0.9 um on iron content in the tuie ample from ROI (the embeing granite, antone an brown oil) i preente. With the increaing of the iron content the pectral tranformation alue ecreae a well. Thi epenence i bae on content of wieprea iron an i one promiing approach for etection of a patial itribution of iron content in the tuy area. Ilie I., 00. Spectrometric Sytem for Solar an Atmopheric Meaurement, E+E, 3-4, 43-47, (in Bulgarian). Kanchea R., D. Borioa, 03. Two Technique for Spectral Clae Decompoition from Their Miture Reflectance. Compt. Ren. Aca. bulg. Sci., T.56, Nо2, pp Krumo A. et al., 983. Spectral Reflectance Meaurement of Volcanite, Granitoie an Gneie, Space Re. in Bulgaria, 4, pp Mihe D., 992. Colour Coorinate of a Mie Cla, Compt. Ren. Aca. bulg. Sci., T.45, N5, pp Petko D., Nikolo H., Georgie G. 05. Thematically Oriente Multichannel Spectrometer (TOMS). Aeropace Reearch in Bulgaria, ol.9, (in pre) Yane Т., R. Kanchea, G. Georgie, 994. Senitiity of Vegetation Inice to alfalfa C-pollution, Compt. Ren. Aca. bulg. Sci., T.47, 8, pp Чимитдоржиев T., В. Ефременко, 998. Об использовании различных индексов вегетации в дистанционном зондировании экосистем. Исследования Земли из космоса, 3, стр ACKNOWLEDGMENTS Thi tuy wa upporte by National Science Fun of Bulgaria uner Contract NZ40/04 an MUNZ502/ CONCLUSIONS The aantage in uing color feature i that the iible pectral range i cloely relate to bio-phyical parameter an that the whole reflectance cure i ue normalize on the pectral itribution of the incient raiation. Beie, λ allow the comparion of lightly iffering color timuli aociate with plant coer change. A iaantage may be the neceity of uing oil-ifferentiate moel. Howeer, thi approach for crop fraction coer etimation can proie ueful information in egetation monitoring. Regreion moel ecribing thi relationhip are erie uing big ata et. Fraction coer alue retriee by λ are with atifying accuracy. Of the ame orer i the coer retrieal accuracy uing pectral ine moel. So both approache are equally applicable an gie better reult when ue together. It might be worth to conier the iea of wier eperimental tuy in orer to tet the preictie potential of color moeling in repect to p retrieal accuracy a well a to inetigate moel enitiity to illumination an atmopheric conition. The preente here promiing reult from a tuy of ifferent pectral unmiing technique oer rock-oil-egetation object in relation to object type an proportion etermination an biophyical propertie retrieal are bae for further analye of larger eperimental ataet from airborne, fiel an laboratory pectral reflectance meaurement. REFERENCE Elige С., Lyon R., 985. Influence of Rock-Soil Spectral Variation on the Aement of Green Bioma. Rem. Sen. En., ol.7,