3D Geospatial modeling of accident scene using Laser Scanner data

Transcription

1 Cvl and Envronental Research ISSN (Paper ISSN -863 (Onlne Vol, No.10, Geospatal odelng of accdent scene usng Laser Scanner data R. Ehgator Irughe 1*, M. O. Ehgator,1 1 Sberan State Geodesy cadey, epartent of Engneerng Geodesy and GeoInforaton Systes, Novosbrsk, Russa. Faculty of asc Scence, epartent of Physcs and Energy, enson- Idahosa Unversty, enn Cty, Ngera. *raphehgator@yahoo.co, 1 geosystes_004@yahoo.co bstract The a of traffc reconstructon s to recreate otor vehcle collson scenes n order to analyze the dynacs of the collson events, to provde evdence n court cases and allow the anufacturers to evaluate the vehcle s desgn. However, at the scene of the accdent t s not known exactly the aount of nforaton that wll be requred for the analyss and often relevant data are ssng. The eergence of terrestral laser scannng has enabled the 3 docuentaton of accdent events n a safer way, as nforaton can be collected wthout any lane closures or traffc nterruptons, and n a ore flexble and faster way, as a sngle user can operate the nstruent n coplete darkness or drect sunlght. The noton of ths paper s to odel accdent scene usng terrestral laser scannng data. Wth the ntersecton-related crashes akng up a hgh proporton of total fatal crashes, there s a need for recordng ther current status n order to prove the desgn and operaton of road ntersectons. Terrestral laser scannng provdes the capablty of recordng such nfrastructures n a fast and relable way, where a nuber of dfferent nforaton, ncludng traffc control features, volues, accdent characterstcs and detaled spatal data, can be easly obtaned. Ths nforaton can then be ntegrated wthn traffc anageent ntegrated systes and be used for accdent preventon purposes. Keywords: Terrestral laser scanner (TLS, Moentu, speed, ccuracy. 1.0 Introducton Traffc accdents can occur whenever sgnfcant defcences, oversghts, errors, ossons, or unantcpated changes are present. ny one of these condtons can be a precursor for an accdent; the only uncertanty s when the accdent wll occur and the degree of the accdent. To conduct a coplete accdent/ncdent nvestgaton, the factors contrbutng to an accdent, as well as the eans to prevent accdents, ust be clearly understood. However, ost are caused. Understandng how to prevent or control traffc accdents requres knowledge of the sequence of events leadng to an accdent, n order to dentfy and pleent counter easures. Therefore, the process of accdent reconstructon can be consdered as a sequence of operatons nvolvng the collecton of data about the road transportaton coponents (road, vehcles and people and contnues through nferences and conclusons about the sequence of events that consttute the accdent and the relatonshp of these coponents durng the events [6] Fve levels of actvty n accdent nvestgaton are: (a reportng, where basc data collecton s used to dentfy and classfy an accdent, (b at-scene nvestgaton, whereby extra data are collected at the accdent scene along wth the results of the accdent, such as arks on the road and debrs, tre arks etc, (c techncal follow-up, whch studes all avalable data relatng to an accdent, such as speed and acceleraton of vehcles, vsblty of vehcles, pedestrans etc, and s undertaken for legal and other specfc purposes, (d professonal reconstructon whch deternes fro the avalable data how the road, drver and vehcle contrbuted to a partcular accdent, and (e cause analyss, whch deternes fro the avalable data why the accdent happened (e.g. defcences of road or vehcle desgn. Clearly, the data collecton and recordng at the accdent scene s the ost crtcal aspect as they are needed n all the aforeentoned fve levels of nvestgaton. Furtherore, traffc recordng systes should be technologcally sophstcated to provde ore tely, fast, accurate, ntegrated, accessble and ore standardzed and unfor data. lso, the easureent process should be as least dsruptve to traffc as possble and provde end products that are easly transfored to drawngs. 39

2 Cvl and Envronental Research ISSN (Paper ISSN -863 (Onlne Vol, No.10, 01 The ost coonly easurng approach s surveyng where easureents of dstances along and offset fro a road edge or centerlne are perfored. Frequently, total statons and laser range fnders are eployed but wth the dsadvantage of beng dsruptve to traffc. GPS surveyng s successfully used but only n unobstructed areas. Recently, close-range dgtal photograetrc or 3 Laser Scannng for Road Safety and Traffc ccdent systes have been developed whch provde fast and accurate data acquston but can be relatvely expensve and coplex to use for local polce and traffc agences[6]. More recently, the eergence of terrestral laser scannng has enabled the 3 docuentaton of accdent events n a safer way, as nforaton can be collected wthout any lane closures or traffc nterruptons, and n a ore flexble and faster way, as a sngle user can operate the nstruent n coplete darkness or drect sunlght. The end products of the laser scanner data nclude 3 anatons of scenes, and even 3 physcal odels that can be used nto the ury roo. The advantage of the 3 dgtal odels s that they provde further help n analysng what happened n a crash, for exaple easurng the vehcle deforaton helps to deterne the speed at pact and other contrbutng factors. Scene capture that s both fast and coplete s another advantage. The huge volues of data collected wth a laser scanner ay not always be used at each level of traffc nvestgaton but certanly allow the return vsts to the accdent scene be ade vrtually[6]. Fgure 1 Soe types of terrestral laser scanners.0 ccuracy of Terrestral Laser Scanner observatons (TLS To achevng the results that eet the specfcatons of a gven proect, the knowledge of the accuracy of the surveyng equpent s nevtable. Surveyng results ust eet certan specfcatons n order to provde the necessary accuracy standards for a certan applcaton. On the other hand, f nstruents and ethods are used whch yeld accuracy far above the needed standard, ths wll result n unnecessary cost and expendture. Therefore, any geoetrc surveyng task coprses not only the dervaton of the relatve postons of ponts and obects but also an estaton of the accuracy of the results [5]. There are dfferent accuraces for the sngle pont easureent. Wth the total staton, the sngle pont accuracy s hgher. successful accdent schee usng a terrestral laser scanner ay call for easureents of hgh precson and accuracy. The nstruent anufacturers quoted precson and accuracy rarely atches the actual capabltes of the nstruent. 3.0 Matheatcal odel of Terrestral Laser Scanner Range of scans s a functon of the laser ntensty and reflectvty of the obect scanned. The rangng capablty of a laser scanner s ore portant than t frst sees. In soe cases, the lack of rangng ablty wll copletely elnate the ablty to do certan proects [1, ]. Rangng errors can be observed when known dstances n range drecton are easured wth the scanner. If scanners are not equpped wth a defned reference pont (such as forced 40

3 Cvl and Envronental Research ISSN (Paper ISSN -863 (Onlne Vol, No.10, ( ( ( S S S S. cos / / / / O O O O α centerng, t s only possble to deterne the range accuracy of laser scanner by coparng the accuracy of the calculated dstance between reflectve arks resulted fro laser scanner and the calculated dstance fro other accurate nstruent (for exaple total staton. The length of sde, fro ts end coordnates, can be calculated by: (1 y dfferentaton equaton (1 and by usng propagaton law, the accuracy of the sde length between two ponts can be deterned by usng the followng forula: ( If the coordnates of laser scanner poston equal (0, 0, 0 at any scan, then the length of sde fro any scanned pont to the laser scanner poston wll be expressed n the for: (3 Then, accuracy of the length of sde fro any ark to the laser scanner by applyng equaton ( can be calculated by usng the error propagaton as: (4 4.0 Horzontal angles (Horzontal Plane s shown n fgure, the horzontal angle α can be calculated fro the geoetry of horzontal trangle O / / as followng: (5

4 Cvl and Envronental Research ISSN (Paper ISSN -863 (Onlne Vol, No.10, 01 TLS Mark (,, / (, S γ О γ А α АВ Horzontal plane S Mark (,, / (, Fgure Scannng two ponts by usng terrestral laser scanner (TLS If the coordnates of laser scanner poston equal (0, 0, 0 at any scan, the equaton (5 can be reconstructed by usng the ponts coordnates as followng: cos α., (6 The accuracy of horzontal angle has the for: α α ( α ( α ( α (. (7 5.0 Vertcal angles (Vertcal Plane Fro each pont n the scanned obect t s possble to deterne the vertcal angle of the laser scanner. If the coordnates of occuped laser scanner staton s (0, 0, 0 then the vertcal angle fro pont (for exaple can be deterned as followng: γ tan 1 ( 4 (8

5 Cvl and Envronental Research ISSN (Paper ISSN -863 (Onlne Vol, No.10, 01 y usng the law of propagaton, the accuracy of vertcal angle can be deterned as followng: γ ( ( (.( ( 4 4 (9 Fgure 3: Leca C10 3 Laser Scanner The ScanStaton C10 fro Leca Geosystes s a versatle 3 laser scannng soluton whch rapdly photographs then easures everythng at a scene, not ust what ay be consdered portant at the te. Ideal for coplex envronents and wth a 100% acceptance record n U.S. Ths s one of the ost useful forensc advances for processng cre scenes snce the creaton of photography. It allows an nvestgator to capture a scene totally and copletely; everythng s preserved fro the oent the scanner s deployed. 6.0 Moentu In classcal echancs, oentu or, equvalently s the product of the ass and velocty of an obect (p v. Lke velocty, oentu s a vector quantty, possessng a drecton as well as a agntude. Moentu s a conserved quantty (law of conservaton of lnear oentu, eanng that f a closed syste s not affected by external forces, ts total oentu cannot change. Moentu s soetes referred to as lnear oentu to dstngush t fro the related subect of angular oentu [7] lthough orgnally expressed n Newton's Second Law, the conservaton of oentu also holds n specal relatvty and, wth approprate defntons, a (generalzed oentu conservaton law holds n electrodynacs, quantu echancs, quantu feld theory, and general relatvty. In relatvstc echancs, non-relatvstc oentu s further ultpled by the Lorentz factor. 43

6 Cvl and Envronental Research ISSN (Paper ISSN -863 (Onlne Vol, No.10, 01 The lnear oentu of a syste of partcles s the vector su of the oent of all the ndvdual obects n the syste [7]: where p s the total oentu of the partcle syste, and v are the respectve ass and velocty of the -th obect, and n s the nuber of obects n the syste. The Total oentu before a crash ust equal the total oentu after a crash. Therefore the nlne crash s gven as [8]: [ W 1 S1] [ W S] [ W1 S3] [ W S4] (10 (11 The angular crash for both cars can be express as follows [ W S1 Snα ] [ W S Snϕ] [ W1 S3 Snϕ] [ W S4 Snϕ] 1 (1 [ W S1 Cosα ] [ W S Cosϕ] [ W1 S3 Cosϕ] [ W S4 Cosϕ] 1 (13 The data fro both cars that are nvolved n accdent are presented n table 1 Table 1 vehcle data Vehcle #1 Vehcle # - 00 pck up 1989 cary Curb weght 311 lbs 3081 lbs Passengers and cargo 1413 lbs 903 lbs Total weght 455 lbs 3984 lbs pproach angle 107 degrees 0 degrees eparture angle 85degrees 67 degrees eparture speed 0 ph 0 ph Rotaton angle 176 degrees 47 degrees stance 9.59feet feet rag factor RR tre locked fro pact oth front tres locked fro pact dusted drag factor Ipact speed.3 or ph or 38 ph Fro equaton (1 the oentu of vehcle can be calculated thus: [ 3984 S 1 Sn0] [ 455 S Sn107] [ Sn67] [ Sn84] 44

7 Cvl and Envronental Research ISSN (Paper ISSN -863 (Onlne Vol, No.10, 01 [ 3984 S 1 0] [ 455 S ] [ ] [ ] [ 3984 S 1 0] [ 455 S ] [ ] [ ] 437.5[ S] S ph lso fro equaton (13 the oentu of vehcle 1 can be calculated thus: [ 3984S 1 Cos0] [ Cos107] [ Cos67] [455 0 Cos85] [ 3984 S1] S S1.33 ph Fro the results presented above, t can be observed that the speed of vehcle (S was found to be 38ph.e. (60.8kph, whle vehcle 1 (S1 was found to be ph.e. 35kph. The results ndcate that vehcle (S approach the bent at an excessve speed thereby lost control. Laser Scannng for Forenscs ffnd Hoeland Securty Fgure 4: 3 Laser scanner crowd ponts of ccdent Scene 45

8 Cvl and Envronental Research ISSN (Paper ISSN -863 (Onlne Vol, No.10, 01 Fgure 5: 3 cloud ponts of ccdent Scene 7.0 Concluson Wth the growng nterest n natonal and nternatonal road safety progras, there s a requreent for relable, accurate, and tely data to ake decsons about traffc safety probles and countereasures. The a of these progras s to docuent and evaluate the characterstcs of traffc accdents and the nteracton of varous coponents n order to support analyss on traffc safety. In the feld of traffc accdent reconstructon, a nuber of easureents tools have been adopted wth terrestral laser scannng beng a prosng technology n ths feld. The greatly reduced on-scene te, resultng to shorter traffc dsrupton perods, and a peranent 3 vsual detaled record of the accdent scene are the notable advantages of terrestral laser scannng. Wth the ntersecton-related crashes akng up a hgh proporton of total fatal crashes, there s a need for recordng ther current status n order to prove the desgn and operaton of road ntersectons. Terrestral laser scannng provdes the capablty of recordng such nfrastructures n a fast and relable way, where a nuber of dfferent nforaton, ncludng traffc control features, volues, accdent characterstcs and detaled spatal data, can be easly obtaned. Ths nforaton can then be ntegrated wthn traffc anageent ntegrated systes and be used for accdent preventon purposes. REFERENCES 1. kca., Gruen. (005: Recent advances n least square 3 surface atchng. Gruen,Kahen H (eds. Optcal 3- Measureent Technques VII, Vol. II, pp lba M., Scaon M. (007: Coparson of technques for terrestral laser Scannng data georeferencng appled to 3- odellng of cultural hertage. In: Proceedngs of the nd ISPRS Internatonal Workshop 3-RCH 007: 3. 3 Vrtual Reconstructon and Vsualzaton of Coplex rchtectures, urch,swtzerland, lba M, Gussan., Roncoron F., Scaon M. (005. Strateges for drect georeferencng of Regl LMS- 40 data. In: Gruen, Kahen H (eds. Optcal 3- Measureent Technques. 46

9 Cvl and Envronental Research ISSN (Paper ISSN -863 (Onlne Vol, No.10, ury Reshetyuk (009. Self-calbraton and drect georeferencng n terrestral laser scannng. octoral thess n Infrastructure, Geodesy Royal Insttute of Technology (KTH epartent of Transport and Econocs vson of Geodesy Stockhol. 6. Vasslos Pagouns, Mara Tsakr, Sprrdon Palaskas, arbara za and Elzabeth alou, Greece ( Laser Scannng for Road Safety and Traffc ccdent Reconstructon. III FIG Congress Traffc Crash Reconstructon case study (003. epartent of Surveyng Engneerng, Unversty of Mchgan, US. bout the authors go to: 47

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