USING PAVEMENT MARKINGS TO SUPPORT THE QA/QC OF LIDAR DATA

Transcription

1 In: Silla U e al (Ed) PIA07. Inernaional Archive of Phoogrammery, Remoe Sening and Spaial Informaion Science, 6 (/W49B) USING PAVEMENT MARKINGS TO SUPPORT THE QA/QC OF LIDAR DATA C. Toh a, *, E. Paka a, D. Brzezinka b a Cener for Mapping, OSU, 116 Kinnear Road, Columbu, OH 41 USA - (oh, eva-paka)@cfm.ohio-ae.edu b Dep. of Civil and Environmenal Engineering and Geodeic Science, OSU, dbrzezinka@ou.edu Commiion I, WG I/ KEY WORDS: LiDAR, LiDAR ineniy, Feaure exracion, QA/QC ABSTRACT: LiDAR echnology became an indipenable airborne mapping ool in recen year and i he primary ource of highly accurae urface daa a large cale. Alhough, he ranging accuracy of he laer enor rongly depend on he urface characeriic, by and large, i fall in o he few cm range. Thi alo implie ha he achieved accuracy of a LiDAR yem, defined in erm of he abolue accuracy of he laer poin, i predominanly deermined by he qualiy of he navigaion oluion (ypically baed on GPS/IMU enor inegraion). Depie ignifican advancemen in navigaion echnologie recenly, o achieve and uain a high accuracy navigaion oluion of an airborne plaform for exended ime i ill a difficul ak. Furhermore, here i no reliable way o ae he poiioning qualiy of he daa capured by any imaging enor yem, which are baed on direc georeferencing. Therefore, uing ome ground conrol i almo mandaory if high accuracy i required. Thi paper inroduce a mehod o ue road pavemen marking a ground conrol ha could be ued for QA/QC. Thee linear feaure are widely available in urban area and along ranporaion corridor, where mo of he governmen and commercial mapping ake place. A key advanage of uing pavemen marking i ha hey can be quickly urveyed wih GPS VRS echnique. 1. INTRODUCTION The inroducion of airborne LiDAR (Ligh Deecion And Ranging) in he lae nineie wa followed by a quick proliferaion of he echnology, and LiDAR i now he primary urface daa exracion mapping echnique. Thi remarkable ucce i mainly due o he fac ha LiDAR daa are explici and he proceing can be highly auomaed plu ha an unprecedened verical accuracy could be obained relaively eaily. The horizonal accuracy of he LiDAR daa wa no a concern in he early ue of hi echnology. In fac, he fir LiDAR daa QA/QC and produc characerizaion effor did only deal wih he verical accuracy (ASPRS, 004). A he LiDAR marke ared o grow rapidly, oon he LiDAR yem howed ruly phenomenal performance improvemen. In le han five year, he pule rae improved by an order and now 100 and 150 khz yem are widely ued (Opech, 006 and Leica, 006) and experimenal wo-pule yem are alo available. More imporanly, he ranging accuracy ha increaed ubanially and now and cloe o he level of aic GPS urvey, i.e., 1- cm for hard urface, which i pracically negligible o he ypical navigaion error budge. Thi remarkable performance poenial of he newer LiDAR yem, combined wih beer operaional echnique, opened he door oward applicaion where large-cale or engineering-cale accuracy i required. A hi poin he georeferencing error budge and, o a leer exen, he enor calibraion qualiy, are criical o achieving engineering deign level accuracy (few cm). Uing ground conrol i an effecive way o compenae for georeferencing and enor modeling error. In addiion, ground conrol can provide for independen and highly reliable QA/QC procee. Thi paper propoe a mehod o ue road pavemen marking a ground conrol o ae he qualiy of he LiDAR daa a well a o improve he poin cloud accuracy by po-proceing. Beyond heir wide availabiliy, he ue of pavemen marking i primarily moivaed by he fac ha hey can be raher eaily urveyed uing GPS VRS (Virual Reference Syem) echnology; he proce i fa, ypically i ake one minue o urvey a poin, and he accuracy, in general, i abou - and - 6 cm horizonally and verically, repecively.. LIDAR ACCURACY AND ERROR CORRECTION TECHNIQUES The error in laer canning daa can come from individual enor calibraion or meauremen error, lack of ynchronizaion, or mialignmen beween he differen enor. Balavia (1999) preen an overview of he baic relaion and error formulae concerning airborne laer canning. Schenk (001) provide a ummary of he major error ource for airborne laer canner and error formula focuing on he effec of yemaic error on poin poiioning. In general, LiDAR enor calibraion include can angle, range calibraion and ineniy-baed range correcion. The LiDAR enor plaform orienaion i alway provided by a GPS/IMU-baed inegraed navigaion yem. The connecion beween he navigaion and LiDAR enor frame i decribed by he mouning bia, which i compoed of he offe beween he origin of he wo coordinae yem and he boreigh mialignmen (he boreigh mialignmen decribe he roaion beween he wo coordinae yem, and i uually expreed by roll, pich and heading angle). To achieve opimal error compenaion ha aure he highe accuracy of he final produc, all of hee parameer hould be calibraed. Since no all of he parameer can be calibraed in a laboraory * Correponding auhor. 17

2 PIA07 - Phoogrammeric Image Analyi --- Munich, Germany, Sepember 19-1, 007 environmen, a combinaion of laboraory and in iu calibraion i he only viable opion for LiDAR yem calibraion. Typical anomalie in he LiDAR daa indicaing yem calibraion error are: edge of he rip could bend up or down (can angle error), horizonal urface have a viible mimach beween he known and he LiDAR poin-defined urface (boreigh mialignmen or navigaion error), verical coordinae of LiDAR poin over fla area do no mach he known verical coordinae of he area (ranging or navigaion error), objec, uch a pavemen marking made of rero reflecive coaing, may how up above he urface level, alhough hey hould pracically have idenical verical coordinae (lack of ineniy correcion of he range daa), ec. The echnique o deec and ulimaely compenae for error fall ino wo broad caegorie baed on wheher hey ue abolue conrol or no. The fir group include mo of he rip adjumen echnique and ome of he enor and boreigh calibraion mehod. The ground conrol-baed echnique encompa comparion o reference urface, uch a parking lo and building, and mehod uing LiDARpecific conrol arge. Srip adjumen mehod primarily minimize he verical dicrepancie beween overlapping rip or beween rip and horizonal conrol urface. Thee rip adjumen can be referred o a one-dimenional rip adjumen mehod (Crombagh e al., 000; Kager and Krau, 001); ie or abolue conrol feaure ued for hi adjumen are fla horizonal urface. The problem wih hi kind of adjumen i ha exiing planimeric error are likely o remain in he daa. Voelman and Maa (001) have hown ha yemaic planimeric error are ofen much more ignifican han verical error in LiDAR daa and, herefore, a D rip adjumen i he deirable oluion minimizing he D dicrepancie beween overlapping rip and a conrol poin. A number of D adjumen mehod have been publihed. Kilian e al. (1996) preened a mehod of ranforming overlapping LiDAR rip o make hem coincide wih each oher uing conrol and ie poin in a way imilar o phoogrammeric block adjumen. Burman (00) reaed he dicrepancie beween overlapping rip a poiioning and orienaion error wih pecial aenion given o he alignmen error beween he IMU and laer canner (Soininen, 005). Filin (00) preened a imilar mehod for recovering he yemaic error; he mehod i baed on conraining he poiion of he laer poin o he urface from which i wa refleced. Toh e al. (00) preened a mehod ha ried o make overlapping rip coincide, wih he primary objecive of recovering he boreigh mialignmen beween he IMU and laer enor. LiDAR-pecific ground conrol arge were inroduced by Toh and Brzezinka (005; Canyi e al., 005). The propoed echnique ue ground conrol arge pecifically deigned for LiDAR daa o provide qualiy conrol for applicaion ha require cm-level, engineering cale mapping accuracy. Simulaion reul confirmed ha he opimal arge i roaion invarian, circular-haped, elevaed from he ground and ha a fla arge wih 1 m circle radiu can provide ufficien accuracy from a poin deniy of abou 5 p/m. Targe larger han m in diameer will no lead o ignifican improvemen. In addiion, a wo-concenric-circle deign (he inner circle ha one-half he radiu of he ouer circle) wih differen coaing can produce coniderable accuracy improvemen in he horizonal poiion. Deail and performance evaluaion can be found in (Canyi and Toh, 007).. LIDAR INTENSITY DATA The inroducion of ineniy daa a few year ago produced unrealiically high iniial expecaion. On one ide, he viualizaion value provided a major help for ineracive proceing, and hu, uer could immediaely benefi from he new ource of daa, a LiDAR ineniy wa comparable o opical image ype of daa ha had been mied by praciioner from he early beginning. On he oher ide, he algorihmic advanage of uing ineniy daa for providing beer LiDAR daa proceing were largely overeimaed. While reearch inanly ared o addre he exploiaion of he new ource of informaion, he problem eemed o be harder han expeced. In imple erm, he major difficuly of working wih LiDAR ineniy daa i he relaive naure of hi ignal. For example, differen urface, daa from differen flying heigh, and differen urface orienaion can produce exacly he ame ineniy value. Therefore, echnique o calibrae he ineniy and range value wih repec o each oher ared o become more common. One of he fir aemp on uing ineniy daa dae back o he ime when LiDAR ineniy daa were no ye commercially available. Maa (001) decribe he exenion of a TIN-baed maching echnique uing reflecance daa (LiDAR ineniy daa) o replace urface heigh exure for he deerminaion of planimeric rip offe in fla area wih ufficien reflecance exure. A an exenion, Voelman (00) offer anoher oluion, kind of a feaure-baed maching, o avoid inerpolaion of he daa, uing linear feaure, gable roof, and diche, modeled by analyical funcion ha can provide accurae offe deerminaion. Laer, reearch inere eered oward convenional claificaion ue of he ineniy daa. Song e al. (00) propoed a echnique o ue ineniy daa for land-cover claificaion. A imilar udy on uing ineniy for glacier claificaion i preened in Luz e al. (00). A recen review of more advanced verion of hee echnique i offered by Haegawa (006). A comprehenive udy on proceing boh range and ineniy daa i provided by Sihole (005). Kaaaalainen e al. (005) provide a review on ineniy daa wih repec o calibraion. Nobrega and O Hara (006) compare wo echnique for filering ineniy daa for objec exracion. Finally, Ahoka e al. (006) preen he reul of a calibraion e on ineniy daa uing he Opech ALTM 100. Figure 1 and how imulaneouly acquired orhoimage and he LiDAR ineniy image, repecively, of an inerecion. The LiDAR poin deniy wa abou 4 p/m wih foo prin ize of 15 cm. Noe ha he pavemen marking in he LiDAR image are quie viible and diinc from he pavemen. Conequenly, if he approximae locaion of he pavemen marking i known, hen heir exracion i a fairly raighforward ak. To illurae ha LiDAR elevaion and ineniy daa are correlaed and ineniy informaion can indicae he preence of ranging error, Figure how he elevaion daa of he ame inerecion. Noe ha he pavemen marking can be een quie well, which conflic wih he fac ha elevaion value of he marking and he pavemen around hem hould be idenical (he few mm hickne of he marking i negligible compared o he few cm ranging accuracy of he laer yem). Thi phenomenon i known and correcion able are available o parially compenae for hi effec. The imporance of hi anomaly from our perpecive i ha during he comparaive analyi laer, he elevaion value of he marking hould be replaced by he average elevaion of he pavemen. 174

3 In: Silla U e al (Ed) PIA07. Inernaional Archive of Phoogrammery, Remoe Sening and Spaial Informaion Science, 6 (/W49B) Sraigh edge Sop bar Curved edge Figure 1. Typical pavemen marking a an inerecion. 4. EXTRACTING PAVEMENT MARKINGS AND USING THEM AS GROUND CONTROL The concep of he propoed mehod, including pavemen marking exracion a well a parameerizaion of he mark baed on LiDAR ineniy daa, he comparion wih ground ruh, and he deerminaion of a ranformaion o correc he poin cloud, analyi of reul, ec., i hown in Figure 4. General aumpion are ha he urvey daa of he pavemen marking are available a priori and he individual poin accuracy, decribing he mark, i known a he cm-level. To achieve good performance, ufficien number of pavemen marking i required wih good paial diribuion. A hi poin only hree ype of pavemen marking are conidered: Sop bar, raigh edge line and curved edge line; Figure 1 how he hree pavemen marking ype. The urvey daa of he pavemen marking i provided a poin obervaion along he cenerline of he marking. The LiDAR daa, including range and ineniy componen, are aumed o be of reaonable qualiy; i.e., he poin cloud accuracy i beer han a meer. Exracion of pavemen marking from LiDAR, baed on ineniy GPS-urveyed ground conrol poin Piecewie weighed lea quare curve Piecewie weighed lea quare curve Maching curve, eablihing a D (D) ranformaion Analyzing reul, baed on magniude and diribuion of reidual, creaing QA/QC repor; if needed, deciding on he complexiy of he ranformaion ha will be applied o he LiDAR poin cloud Figure. LiDAR ineniy image. Figure. LiDAR elevaion daa. Figure 4. Block diagram of he propoed mehod. Baed on he comparion of he wo decripion of pavemen marking, one obained from he GPS urvey and he oher one form LiDAR ineniy daa, offe and orienaion difference can be deeced. Depending on he magniude of he oberved difference and heir paial diribuion, a variey of correcion can be applied o he LiDAR poin cloud o improve he poin poiion accuracy. For example, if here i a imilar verical hif deeced a he conrol feaure, a common verical offe correcion can be applied. If he amoun of verical hif deeced varie by locaion and/or combined wih non negligible horizonal difference, a more complex model, uch a a D imilariy ranformaion can be applied. Noe ha aeing he horizonal accuracy i difficul, a i i mainly defined by he fooprin of he laer pule, which depend on flying heigh and beam convergence; in addiion, he impac of objec urface characeriic could be alo ignifican. The ranformaion baed on he oberved difference can be formulaed on boh, poin- and linear feaure-baed lea quare adjumen echnique. The convenional conrol poin-baed mehod i raher raighforward; imilar o an abolue orienaion of a ereo model wih fixed cale. Linear feaure-baed orienaion i le widely ued, bu could be feaible given he availabiliy of mached linear feaure. Finally, if he difference are ou of 175

4 PIA07 - Phoogrammeric Image Analyi --- Munich, Germany, Sepember 19-1, 007 he uual range (gro error), he proce can indicae yem malfuncioning. In our cae, he poin-baed ranformaion i direcly no applicable, a here i no poin-o-poin correpondence beween he wo poin e ha decribe he ame linear feaure. Auming ha he wo repreenaion provide an adequae decripion of he ame hape, he problem i imply how o mach wo free-hape curve. In he following, he wo key componen of he propoed mehod, curve fiing and maching are dicued a deail. 4.1 Curve fiing The exraced LiDAR poin of he pavemen marking and heir urveyed daa hould be modeled a linear feaure in order o be mached wih each oher. The eleced mehod i an exended verion of he algorihm, originally propoed by Ichida and Kiyono in 1977, and i a piecewie weighed lea quare curve fiing baed on cubic (hird-order polynomial) model, which eemed o be adequae for our condiion. To handle any kind of curve, defined a he locu of poin f(x, y) = 0 where f(x, y) i a polynomial, he curve fiing i performed for maller egmen in local coordinae yem, which are defined by he end poin of he curve egmen. The primary advanage of uing a local coordinae yem i o avoid problem when curve become verical in he mapping coordinae yem. Figure 5 how he concep of he local coordinae yem ued for curve fiing; obviouly, he fiing reul a well a he fiing conrain are alway convered forh and back beween he local and mapping coordinae frame. S(x) Figure 6. Piecewie weighed lea quare curve fiing mehod. The core proceing include he following ep: 1) a S and b S, he coefficien of he econd and hird order erm of he fied curve for inerval i are eimaed; conider he conan erm (y S ) and he coefficien of he fir order erm (m S ) fixed, known from he curve fiing from he previou egmen. In he adjumen, he poin in inerval i + i+ i 1 (pa, preen, and fuure daa poin) are ued, ) he value (y ) and he lope (m ) a x= are compued; hee value a fixed conrain are ued in he curve fiing for he nex egmen, and ) ep 1 i repeaed o proce he nex egmen. Sep 1 Sep Sep i 1 y m S k (x) i y m y y m ( x ) = a ( x ) + b ( x ) LS for poin in inerval i ˆ ˆ 1 + i + i a, b ˆ S ( x) y m ( x ) aˆ k = + + ( x ) + b ( x ) x = yˆ = Sk ( ) = y + m ( ) + aˆ ( ) + bˆ ( ) mˆ Sk ( ) m aˆ ( x ) bˆ = = + + ( x ) y = yˆ and m = mˆ Sk + 1( x) y m ( x ) = a ( x ) + b ( x ) LS for poin in inerval i + i + i aˆ, bˆ 1 i S k+1 (x) i 1 i i x 4. Maching curve Figure 5. The curve fiing i done in local coordinae yem, oriened o curve egmen. The main ep of he piecewie cubic fiing (PCF) proce are horly dicued below; he noaion ued in he dicuion i inroduced in Figure 6. To achieve a mooh curve, he curve fiing o any egmen i conrained by i neighbor by enforcing an idenical curvaure a he egmen connecion poin; in oher word, PCF polynomial i coninuou wih i fir derivaive a connecion poin x=, x=, ec. The equaion decribing he hird-order polynomial and i fir derivaive are: Sk (x) = y + m (x ) + a (x ) + b (x ) lope = S (x) = m + a (x ) + b (x ) k Ieraive regiraion algorihm are increaingly ued for regiering D/D curve and range image recenly. The wellknown Ieraive Cloe Poin (ICP) algorihm (Bel and McKay, 199; Madhavan e al., 005) i adoped here o mach curve decribing pavemen marking obained from LiDAR ineniy and GPS meauremen. The ICP algorihm find he be correpondence beween wo curve (poin e) by ieraively deermining he ranlaion and roaion parameer of a D/D rigid body ranformaion. min ( R, T ) M i ( RDi + T ) i Where R i a * roaion marix, T i a *1 ranlaion vecor and ubcrip i refer o he correponding poin of he e M (model) and D (daa). The ICP algorihm can be ummarized a follow: 1. For each poin in D, compue he cloe poin in M. Compue he incremenal ranformaion (R, T). Apply incremenal ranformaion from ep () o D 4. If relaive change in R and T are le han a given hrehold, erminae, oherwie go o ep (1) Our D ICP wa implemened in Malab and pace-cale opimizaion wa incorporaed o reduce execuion ime. 176

5 In: Silla U e al (Ed) PIA07. Inernaional Archive of Phoogrammery, Remoe Sening and Spaial Informaion Science, 6 (/W49B) 5. EXPRIMENTAL RESULTS To perform an iniial performance e of he propoed mehod, a ypical inerecion wa eleced from a recenly flown LiDAR urvey, where GPS-urveyed pavemen marking were available. Figure 7 how he area wih linear pavemen marking meaured from he LiDAR ineniy daa a well a he GPS poin. Noe he clearly viible mifi beween he wo poin e; he horizonal accuracy of he GPS-urveyed poin, provided by he Ohio Deparmen of Tranporaion VRS yem i 1- cm. The reul of he ICP-baed curve maching for all he four curve line i hown in Figure 9. Viually, he ranformaion how a good fi; he blue poin nicely fall on he GPS-defined curve. Noe ha he original curve poin, derived from LiDAR, moved o he conrol curve imilarly, a oppoed o hey would move if he individual curve had mached. Figure 10 how he reul of curve maching for he lower raigh pavemen line, including boh he ranformaion reul; a expeced he individual ranformaion implemen a perpendicular projecion o he conrol curve. The LiDAR poin-baed decripion of he pavemen marking wa obained by filering. The earch pace wa defined by he GPS conrol poin (pavemen marking are aumed o be wihin ±1 m of heir rue locaion) and ineniy hreholding wa ued o exrac he linear feaure; he road pavemen ha low ineniy value while he pavemen marking exhibi higher ineniie. The hrehold i adapively defined by analyzing he hiogram of he LiDAR ineniy value of he road urface around he urveyed road pavemen marking and/or by examining ineniy value of road urface profile (LiDAR can-line). Figure 9. Curve maching baed on all he four curve; magena: curve fied o conrol poin, red: GPS conrol poin, blue: curve poin derived from LiDAR, and cyan: ranformed curve poin (derived from LiDAR). Figure 7. Inerecion wih pavemen marking meaured from LiDAR ineniy daa (whie) and GPS-urveyed (blue). In he curve-fiing ep, boh repreenaion of he linear feaure are compued according he algorihm decribed in 4.1. Figure 8 how one example of he fied curve for he we curb line. Figure 8. Curve fiing baed on LiDAR and GPS poin. Figure 10. Comparing individual and combined curve fiing o a raigh feaure; magena: reference curve, cyan: poin derived from LiDAR, blue: ranformed poin baed on ingle curve maching, and black: ranformed poin baed on maching all he four curve ogeher. To ae in acual number he accuracy of he ranformaion, obained by he ICP-baed curve maching, correpondence beween he LiDAR-derived curve and he conrol curve were eablihed. Since he wo curve in general are no oally idenical, even afer he final ICP ieraion, he ranformed LiDAR-derived poin are cloe bu no necearily fall on he conrol curve. However, he locaion of he ranformed LiDAR-derived poin repreen he be fi o he conrol curve in lea quare ene. Therefore, hee poin are projeced o he cloe poin of he conrol curve, and hen hey are conidered a conjugae poin. The ranformaion parameer beween hee wo poin e (he original LiDARderived poin and heir correponding poin on he conrol curve) are calculaed in a lea quare adjumen. In hi compuaion, he ranformaion parameer for he e daa were eimaed a σ X = ± 0.01m, σ Y = ± 0.017m, and σ angle = ± 1.95 arcmin, indicaing ha a good mach wa found wih he 177

6 PIA07 - Phoogrammeric Image Analyi --- Munich, Germany, Sepember 19-1, 007 ICP mehod for he paially well diribued e daa e. The numerical value, including he ranformaion parameer, error erm, and diperion marix are lied in Table I and II. ICP-adjued reul [m, ] X Y ϕ Table I. Tranformaion reul (D). Tranformaion parameer Eimaed accuracy [cm, ] e-00 * Table II. A poeriori diperion marix. The ~ cm horizonal accuracy i reaonable given he fac ha he GPS-urveyed poin are known a 1 cm-level accuracy and he LiDAR-baed pavemen marking poiioning accuracy i eimaed a he few cm range. 6. CONCLUSION The inroduced mehod o auomae he ue of pavemen marking a ground conrol howed good iniial performance. Boh he curve fiing and ICP-baed maching delivered robu reul. Furher reearch will conider he exenion of echnique o D. Reference: Ahoka, E., Kaaalainen, S., Hyyppa, J. and Suomalainen, J., 006. Calibraion of he Opech ALTM 100 Laer Scanner Ineniy Daa Uing Brighne Targe, Proceeding of ISPRS Commiion I. Sympoium. ASPRS LiDAR Commiee, 004. ASPRS Guideline Verical Accuracy Reporing for LiDAR Daa hp:// _Accuracy_Reporing_for_Lidar_Daa.pdf Balavia, E.P., Airborne Laer Scanning: Baic Relaion and Formula. ISPRS Journal of Phoogrammery & Remoe Sening, Vol. 54: Bel, P. J. and McKay, N. D. A mehod for regiraion of -d hape. IEEE Tran. Pa. Anal. and Mach. Inel. 14(), pp 9-56, Feb 199. Burman, H.,00. Laer Srip Adjumen for Daa Calibraion and Verificaion. Inernaional Archive of Phoogrammery and Remoe Sening, 4 (Par A): Crombagh, M. J.E., R. Brügelmann, E.J. de Min, 000. On he Adjumen of Overlapping Srip of Laeralimeer Heigh Daa. Inernaional Archive of Phoogrammery and Remoe Sening,, (Par B/1):4-1. Canyi N, Toh C., Grejner-Brzezinka D. and Ray J., 005. Improving LiDAR daa accuracy uing LiDAR-pecific ground arge, ASPRS Annual Conference, Balimore, MD, March 7-11, CD-ROM. Canyi, N. and Toh, C., 007. Improvemen of LiDAR Daa Accuracy Uing LiDAR-Specific Ground Targe, Phoogrammeric Engineering & Remoe Sening, Vol. 7, No. 4, pp Filin, S., and Voelman, G., 004. Adjumen of Airborne Laer Alimery Srip. Inernaional Archive of Phoogrammery, Remoe Sening and Spaial Informaion Science 4 (Par B) pp Haegawa, H., 006. Evaluaion of LiDAR Reflecance Ampliude Seniiviy Toward Land Cover Condiion, Bullein of he Geographical Survey Iniue, Vol. 5. Ichida, K. and Kiyono, T Curve Fiing wih One-Pa Mehod wih a Piecewie Cubic Polynomial, ACM Tranacion on Mahemaical Sofware, Vol., No., pp Kager, H. and Krau, K., 001. Heigh Dicrepancie beween Overlapping Laer Scanner Srip. Proceeding of Opical D Meauremen Technique V, Vienna, Auria: Kaaalainen, S., Ahoka, E., Hyyppa, J. and Suomalainen, J., 005. Sudy of Surface Brighne from Backcaered Laer Ineniy: Calibraion of Laer Daa, IEEE Geocience and Remoe Sening Leer, (): Kilian J., Haala, N., Englich, M., Capure and Evaluaion of Airborne Laer Scanner Daa. Inernaional Archive of Phoogrammery and Remoe Sening, 1 (Par B):8-88. Leica Geoyem, ALS50, hp://gi.leica-geoyem.com Luz, E., Gei, Th. and Söer, J., 00. Inveigaion of Airborne Laer Scanning Signal Ineniy on Glacial Surface - Uilizing Comprehenive Laer Geomery Modeling and Orhophoo Surface Modeling (A Cae Sudy: Svariheibreen, Norway), proceeding of ISPRS Commiion III, WG. Maa, H.-G., 001. On he Ue of Pule Reflecance Daa for Laercanner Srip Adjumen. Inernaional Archive of Phoogrammery, Remoe Sening and Spaial Informaion Science, (Par /W4): Madhavan, R., Hong, T., Meina, E. Temporal Range Regiraion for Unmanned Ground and Aerial Vehicle, Journal of Inelligen and Roboic Syem, Volume 44, Number 1 / Sepember, 005, pp Nobrega, R. and O Hara, C., 006. Segmenaion and Objec Exracion from Anioropic Diffuion Filered LiDAR Ineniy Daa. Opech, ALTM 100AE, 006, Schenk, T., 001. Modeling and Analyzing Syemaic Error in Airborne Laer Scanner. Technical Noe in Phoogrammery, vol. 19. The Ohio Sae Univeriy, Columbu, USA. Sihole, G., 005. Segmenaion and Claificaion of Airborne Laer Scanner Daa, Publicaion of Geodey 59, Nederlande Commiie voor Geodeie, Delf (184 page). Song, J-H., Han, S-H., Yu, K, and Kim, Y., 00. Aeing he Poibiliy of Land-Cover Claificaion Uing LiDAR Ineniy Daa, Inernaional Archive of Phoogrammery, 4. pp. 4. Toh C., Canyi N. and Grejner-Brzezinka D. 00. Auomaing he Calibraion of Airborne Mulienor Imaging Syem, Proc. ACSM-ASPRS Annual Conference, Wahingon, DC, April 19-6, CD ROM. Toh, C. and Grejner-Brzezinka, D., 005. Geo-referenced Digial Daa Acquiiion and Proceing Syem Uing LiDAR Technology Final repor, ODOT Sae Job No Voelman, G., and Ma, H.-G., 001. Adjumen and Filering of Raw Laer Alimery Daa. Proc. OEEPE Workhop on Airborne Laercanning and Inerferomeric SAR for Deailed Digial Elevaion Model. OEEPE Publicaion 40, Sockholm, Sweden. pp Voelman, G., 00. On he Eimaion of Planimeric Offe in Laer Alimery Daa. Inernaional Archive of Phoogrammery and Remoe Sening, 4 (Par A): Voelman, G., 00. Srip Offe Eimaion Uing Linear Feaure. rd Inernaional LIDAR Workhop, Ocober 7-9, Columbu, hp:// bu.pdf 178