EVALUATION OF SPOT DATA FOR TOPOGRAPHIC MAPPING WITHOUT GCP. Rutaro Tateishi, Youichoro Kuronuma and Fujio Anzai

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1 EVALUATON OF SPOT DATA FOR TOPOGRAPHC MAPPNG WTHOUT GCP Rutar Tateishi, Yuichr Kurnuma and Fuji Anzai Remte Sensing and mage Research Center Chiba University -33 Yayi-ch, Chiba 260 Japan ABSTRACT Stere triplet f Level A SPOT panchrmatic CCT images were studied t cmpute three dimensinal crdinates f the crrespnding pints n the earth surface using n grund cntrl pint. Only gemetric data such as satellite psitin, velcity and lk directin were used fr the cmputatin f the crdinates. t is fund ut that the abslute accuracy (mean) is mre than several hundred meters but that the relative accuracy (standard deviatin) is less than 0 meters in all X, Y and Z directins. This study shws the ptential f SPOT data t prduce relative tpgraphic map in the areas where GCP is nt available.. ntrductin Since SPOT stere images were available, there have been many researches n cartgraphic applicatin using SPOT images bth by whlly digital methd and by phtgrammetric instruments. Under the tendency that mst researches in bth methds use GCP, this paper aims t study the ptential f SPOT data fr tpgraphic mapping by digital methd withut GCP at the view pint f accuracy_ 2. SPOT images The fllwing stere triplet images cvered Mt. Fuji in Japan were used in this study. Fig. shws viewing angles and angles between vertical lines frm three satellite psitins. Spectral mde Sensr Obsevatin date Viewing angle Prcessing level Path-rw ( ) Panchrmatic HRV2 March 7 ' degree East A ( 2 ) Panchrimatic HRV2 March 8 ' degree West A ( 3 ) Panchrmatic HRV March 7 ' degree East A

2 3. Check pints The crrespnding pints in the three images and tpgraphic map with the scale f :2,500 were cllected manually. 22 gd crrespnding pints were selected fr check pints frm the riginally cllected 63 pints. Fig. 2 shws the lcatins f the check pints in the image. Plane rectangular crdinates, elevatin and image crdinates f the check pints were read frm the map and images. 4.. Methdlgy 4. Cmputatin f three dimensinal crdinates f the check pints Basically, three dimensinal crdinates f the check pints are cmputed as the intersectin f the viewing line which is defined by satellite psitin and viewing directin. () Viewing line The satellite psitin and viewing directin(lk directin) f a specific pixel in a image in the gecentric crdinate system are derived frm the image crdinates f the pixel and gemetric da ta recrded in SPOT CCT by the flw shwn in Fig. 3. (2) ntersectin The intersectin f tw viewing lines in stere pair is defined as the middle f the shrtest line segment between the tw viewing lines. The intersectin f three viewing lines in stere triplet was defined by the fllwing three methds in this study. a) Mean methd b) Weighted mean mehd c) Least square mehd By the methd a), intersectin is defined as ( (X +X2+X 3 )/3, (Y +Y 2 +Y 3 )/3, (Z+Z2+Zs)/3 ) where O<t,Y t,zi)(i=,3) is the intersectin f tw viewing lines in three cmbinatins f stere pairs. By the methd b), intersectin is defined as ( (W*X+W2*X2+WS*Xs)/(W+W2+W3), (W*Vi+W2*V2+WS*Vs)/(W+W2+WS), (W*Z+W2*Z2+W3*Z3)/(W+W2+W3) ) where W'j (i=,3) are the weights which are equivalent t B/H ratis f three cmbinatins f stere pairs. By the methd c), intersectin is defined as the pint which has the least square value f three distances t the three viewing lines. 4.2 Use f cllinearity equatins By using cllinearity equatins at the crrespnding pints, satellite psitins and viewing directins are 406

3 adjusted relatively and accuracy f intersectin is expected t becme better. There are many ways t assume unknwn parameters which are included in satellite psitin and viewing directin. One can assume time-variant parameters. Hwever we assume here very simple time-invariant parameters f (dx i,dy i,dz i ) and (k\,pi,wi) (i=,3 : image N.) as fllws. (dx,dyhdz i ) : parallel shift f satellite psitin Xi Xieet dx Vi Yieet dy i Z\ = Z\eet + dz i (Xi,Y\,Zi) : relatively adjusted satellite psitin used fr the cmputatin f intersectin (Xieet,V!eet,Zieet) : satellite psitin frm SPOT CCT in the gecentric cdinate system (k,pt,wi) : attitude angle in the lcal rbital crdinate system Three cases (P-P3) fr stere pair and three cases (T- T3) fr stere triplet were cnsidered as is shwn in Table. Table Unknwn parameters fr relative adjustment i Parameters Case lst image 2nd image 3rd image dx i dy i dz i k i Pi Wi dx 2 dy 2 dz 2 k2 P2 W2 dx s dy s dz s ks Ps Ws P 0 P2 0 P3! 0 T T2 i T3 ~ 0 ~ ~ ~ ~ j i Parameters are fixed and nt cnsidered fr relative adjustment. The value f these parameters is zer. Unknwn parameters fr relative adjustment P-P3 Cases fr stere pairs Tl-T3 Cases fr stere triplet 5. Results cmputed intersectins f the 22 check pints in the gecentric crdinate system by varius methds were transfrmed t the map crdinates and elevatins and calculated lcatin errrs cmpared with the map crdinates frm :2,500 tpgraphic map_ The hrizntal errrs in the map crdinate system were transfrmed t Xc(crss track directin: apprximately east) and Ya(alng track directin 407

4 : apprximately suth) crdinates. Table 2 shws abslute accuracy (mean) and relative accuracy (standard deviatin) in the case f stere pairs withut using cllinearity equatins. Table 3 shws the ne in the case f stere triplet withut usig cllinearity equatins. Wrse accuracies were btained by the methd using cllinearity equatins than the methd nt using cllineari ty equa tins. 6. Cnclusins () n the case f stere pairs, fairly gd relative accuracies were btained. The relative accuracies in the Xc and Y a directins are independent n B/H rati, while the ne in the Ze directin is dependent n B/H rati. (2) n the case f stere triplet, very gd relative accuracies within 0 meters in all Xc' Y a and Ze directins were btained by the least square methd r the weighted mean methd. (3) Thugh the methd using cllinearity equatins wuld be cnsidered t have a pssibility t imprve relative accuracy, wrse relative accuracies were btained. (4) The relative accuracies btained by stere triplet shws the ptential f SPOT data t prduce relative tpgraphic map in the area where GCP in nt available. Reference Galtier, B., 987. Operatinal prductin chain f tpgraphic maps at the scale f /50000 frm SPOT imagery. Dcument f SPOT meeting at Singapre in Dec. 7-0 Knecny, G., P.Lhmann, H.Engel and E.Kruck, 987. Evaluatin f SPOT imagery n analytical phtgrammetric instruments. Phtgrammeric Engineering and Remte Sensing, Vl.53,NO.9,pp Millt, M., S.Gavann and P.Rebillard, 987. Digital terrain mdel cmputatin using SPOT data. Prceedings f the 8th Asian Cnference n Remte Sensing, pp.(3-2- )-(3-2-8) Tateishi, R., F.Anzai, Y.Kurnuma and K.Tsuchiya, 987. Gemetric Crrectin f SPOT mage. Prceedings f the 8th Asian Cnference n Remte Sensing, pp.(p-2- )-(p-2-0) 408

5 3/7 3/7 3/8.~---. 3', 9 ~...<---- 5".0 Fig. Viewing angles f stere triplet images Fig. 2 Lcatins f check pints 409

6 () Lk! angi es (L) (0) Lk directin (L) (2) Pixel N. (3) (4) Line Scene N. parameters (02) Observatin time (03) Satel J i te psitin (5) Sate! i te! psi ti n data, (04) Satel J i te velcity (6) Sate! lite velcity data (7) Oifference f the tw systems (06), Lk direct i n! (07) Ll< directin (j) (08) Satell ite psitin CD (ll)~(9) nput data (0)--(00) Oerived data (L) Lcal rbital crdinate system SPOT gecentric crdinate system (j) japan gecentric crdinate system Fig. 3 Flw f cmputing satell ite psitin and viewing directin 40

7 Table 2 Abslute and relative accuracy in the case f stere pairs \ \ View i ng ang es B H (degree) ra t i , , , -5.4 Abs ute accu racy Re at i ve accu racy (mean) (standard deviatin) Xc(east)! Ya(suth) Ze(e eva t in) i ' unit meter Table 3 Abslute and relative accuracy in the casef stere triplet Abslute accuracy Relative accuracy Viewing angles Methd! (mean) (standard deviatin) (degree) Xc(east) Ya(suth) Ze(elevatin) +23.8, -4.3 a) and -5.4 b) -656 / c) -79 / a) : Mean methd b) : Weighted mean methd c) : Least square methd unit meter 4

TILTED PHOTOGRAPHS DEFINITIONS. Center for Photogrammetric Training Ferris State University

TILTED PHOTOGRAPHS DEFINITIONS. Center for Photogrammetric Training Ferris State University TILTED PHOTOGRAPHS Center fr Phtgrammetric Training Ferris State University RCB DEFINITIONS Nadir pint (n) Grund nadir pint (N) Principal plane Principal line Azimuth (α) Tilt (t) Swing (s) Church angles