Integrating airborne LiDAR dataset and photographic images towards the construction of 3D building model

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1 IOP Conference Seres: Earth and Envronmental Scence OPEN ACCESS Integratng arborne LDAR dataset and photographc mages towards the constructon of 3D buldng model To cte ths artcle: R Idrs et al 2014 IOP Conf. Ser.: Earth Envron. Sc Related content - Arborne LIDAR pont cloud tower nclnaton judgment Chen lang, Lu zhengjun and Qan janguo - Pxel-based and object-orented classfcatons of arborne LDAR and hgh resoluton satellte data for buldng extracton F Al-Nahas and H Z M Shafr - A comprehensve framework of buldng model reconstructon from arborne LDAR data Y Xao, C Wang, X H X et al. Vew the artcle onlne for updates and enhancements. Ths content was downloaded from IP address on 03/10/2018 at 19:45

2 8th Internatonal Symposum of the Dgtal Earth (ISDE8) Integratng arborne LDAR dataset and photographc mages towards the constructon of 3D buldng model R Idrs1, Z A Latf, J R A Hamd, J Jaafar and M Y Ahmad Centre of Studes for Surveyng Scence & Geomatcs, Faculty of Archtecture, Plannng and Surveyng, Unverst Teknolog MARA, Shah Alam, Selangor D.E. Malaysa E-mal: jaslna01@yahoo.com Abstract. A 3D buldng model of man-made objects s an mportant tool for varous applcatons such as urban plannng, flood mappng and telecommuncaton. The reconstructon of 3D buldng models remans dffcult. No unversal algorthms exst that can extract all objects n an mage successfully. At present, advances n remote sensng such as arborne LDAR (Lght Detecton and Rangng) technology have changed the conventonal method of topographc mappng and ncreased the nterest of these valued datasets towards 3D buldng model constructon. Arborne LDAR has proven accordngly that t can provde three dmensonal (3D) nformaton of the Earth surface wth hgh accuracy. In ths study, wth the avalablty of open source software such as Sketch Up, LDAR datasets and photographc mages could be ntegrated towards the constructon of a 3D buldng model. In order to realze the work an area comprsng resdental areas stuated at Putrajaya n the Klang Valley regon, Malaysa, coverng an area of two square klometer was chosen. The accuracy of the derved 3D buldng model s assessed quanttatvely. It s found that the dfference between the vertcal heght (z) of the 3D buldng models derved from LDAR dataset and ground survey s approxmately ± 0.09 centmeter (cm). For the horzontal component (RMSExy), the accuracy estmates derved for the 3D buldng models were ± 0.31m. The result also shows that the qualtatve assessment of the 3D buldng models constructed seems feasble for the depcton n the standard of LOD 3 (Level of detals). 1. Introducton 3D buldng models have long been useful and requred n a varety of applcatons and act as an mportant n geographc nformaton systems, for urban plannng applcatons, vrtual toursm, analyss of urban clmate and traffc plannng due to ts capabltes n showng real-world features and phenomena n three dmensons. 3D s a new level of spatal data n a dgtal world [1]. Currently, tradtonal method of ground survey to gather buldng nformaton towards the creaton of 3D models n urban areas requres enormous tme; s very costly and labor ntensve. As an alternatve to dervng buldng parameters manually, arborne LDAR datasets are made avalable and the fuson of these datasets wth aeral mage towards 3D buldng constructon seems feasble. LDAR technology enables large area to be surveyed wth three dmenson (3D) or (x, y, z) nformaton for the constructon of Dgtal Surface Model (DSM) wth hgh accuracy n a short delvery tme, wth vertcal accuraces reported of less than 15 centmetres [2]. LDAR ntegrates 1 To whom any correspondence should be addressed. Content from ths work may be used under the terms of the Creatve Commons Attrbuton 3.0 lcence. Any further dstrbuton of ths work must mantan attrbuton to the author(s) and the ttle of the work, journal ctaton and DOI. Publshed under lcence by Ltd 1

3 8th Internatonal Symposum of the Dgtal Earth (ISDE8) three matured technologes: a rugged compact laser scanner, a hghly accurate Inertal Navgaton System (INS) and the Global Postonng System (GPS) [3] as a depcted n Fgure 1. Fgure 1. Arborne LDAR [15]. Integratng these subsystems nto a sngle nstrument, a 3D data pont cloud s collected. It s possble to rapdly produce an accurate DSM of the terran beneath the flght path of the arcraft wth samples the surface of an urban ste n 3 dmensonal [4]. Certanly, ths technology has become an accurate, cost-effectve for collectng topographc elevaton data LDAR DSM for large areas whch wll eventually benefts a dversty of applcatons namely, forest [5], archtecture, town planners, telecommuncatons and cty councls wth hgh accuracy n a short delvery tme [6]. 2. Study area and data The study area chosen for the study s wthn the Klang valley stuated at Putrajaya, Malaysa. The choces of study area are based on the followng crtera; the area exhbts a varaton n topography (heght) and experencng rapd development especally for resdental areas. The LDAR data tle for the study area conssts of 2 x 1 km was extracted from the orgnal dataset wth a grd spacng of less than 1m nterval. The LDAR datasets were acqured usng Brtsh Nomad 2 arcraft wth frst class nfrared laser sensor (Optech System) n The LDAR DSM and photographc mage are shown n Fgure 2 and Fgure 3 respectvely. Front vew Back vew Top vew Sde vew Fgure 2. LDAR DSM. Fgure 3. Photographc mage Control ponts and feld vector lne Fgure 4 shows control ponts and vector lnes were establshed wthn the study area whch acts as reference ponts for the quanttatve assessment. Forty two (42) well-defned ponts (control ponts) were observed usng Global Postonng System (GPS) and tachometrc surveyng method n the determnaton of the control ponts wthn the survey area (Putrajaya). For the horzontal accuracy (RMSExy) assessment, the dfferent at known poston (x, y) for the buldng edges on LDAR DSM are nvestgated. Forty (40) ponts was establshed to represent vector lne s dentfed to compute RMSExy. 2

4 8th Internatonal Symposum of the Dgtal Earth (ISDE8) - Dstrbuton of control ponts - vector lne from ground data - vector lne from LDAR DSM Fgure 4. The locaton of control ponts and vector lnes on Lght Detecton And Rangng DSM. 3. Methodology The step taken to accomplsh the task n the reconstructon of 3D buldng models s shown n Fgure 5. The result also shows the 3D buldng models from standard LOD 3 (Level of detals)[7]. LDAR DSM Buldng footprnts Buldng character Generalsaton Slope Aspect Segmentaton Roof of Buldng Valdaton (RMSE) LDAR data (x,y,z) GPS derved ground data (x,y,z) Photographc mage 3D model Accuracy of 3D buldng model Fgure 5. Workflow for reconstructon of 3D buldng models. 3

5 8th Internatonal Symposum of the Dgtal Earth (ISDE8) Referrng to Fgure 5, Arborne LDAR pont clouds were frstly converted nto a DSM to retreve the x, y and z nformatons are the frst step of the process. In ths study, three (3) processes were carred out to construct of 3D buldng models namely extracton of buldng footprnts, generalzaton and segmentaton. Hence, wth derved slope and aspect from Arborne LDAR DSM represent a good way for the detecton of buldng roof ponts. The generalsaton proses of buldng footprnt are shown n Fgure 6 below. (a) (b) (c) (d) Fgure 6. (a) Orgnal buldng footprnt, (b) generalzed buldng, (c) clpped and (d) segmented pont cloud. The Douglas Pucker algorthm [8] has been appled to reduce lne beng performed by removng ntermedate vertces n generalzaton process (Fgure 6(a)). The removal of ntermedate vertces was done by selectng the mnmum subsequence of the orgnal vertces and usng the outer vertces to create the generalzed lne. The generalzed buldng footprnts were necessary for applcaton of the segmented pont cloud (Fgure 6(b)). If a segment s not known to be part of a buldng t can descrbe other objects lke trees or cars [9]. The pont cloud clpped (Fgure 6(c)) from the generalzed buldng footprnt, were then segmented and converted to ASCII format. In the segmentaton process the ponts reflected by each of the faces are grouped nto a segment whch dentfed by a number or a colour, (Fgure 6(d)). The generalzaton and segmentaton of buldng footprnts combned wth the slope and aspect of buldng classfcaton n order to produce 3D models [10]. In general, slope s the angle between a 3D trangle formed by three random ponts on the surface of a 3D model and the horzontal plane whle aspect s the downslope drecton of the trangle between three random ponts on the surface of a 3D model. As a result, the roofs of a buldng can be detected and then wll be calculated from LIDAR ponts fallng onto t. Meanwhle, LDAR DSM (x,y,z) were used to construct the 3D buldng models, the heght values wth ground data (tacheometrc) are beng calculated. The output of the created s a LoD 0 3D model wth vald accuraces (Table 1). It s because the 3D data n GIS contan x, y and z [11].Ths results n a LoD 1 model by mplementng detecton of footprnt and reconstructon of a roof shape n LOD 2. Unlke natural landscape features, buldngs created by humans are relatvely regular. Moreover, man-made structures are better represented n 3D of vector models [1]. 3D geometrc shapes are normally constructed by exstng GIS,AutoCAD, and photogrammetry methods. In ths study, 3D geometrc shapes of buldngs are edted and extracted from SketchUp wth the selected locaton va geo-locaton functon of SketchUp nterface where the buldng models s obtaned based on heght and wdth of LDAR DSM. Afterwards, these 3D buldng models exported as COLLADA fles [12]. Fnally, the COLLADA fles converted n ArcGIS 10. Fgure 7 shows the reconstructon of 3D buldngs usng SketchUp software [13] n LOD 3 usng photographc mage. 4

6 8th Internatonal Symposum of the Dgtal Earth (ISDE8) Descrpton of nformaton LDAR DATASET (x,y,z) (3D vew) Constructon of 3D model (Sketch Up) Photographc mage Front Footprnt Back Sde Block Top 3D vew Fgure 7. Reconstructon of 3D modelng ntegrated wth photographc mage and Lght Detecton And Rangng dataset. 3D buldngs constructed n ths study were assessed quanttatvely. Quanttatve assessment ncludes the computaton of Root Mean Square Errors (RMSE) of well defne measurements such as buldng heghts, dmensons and the dsplacement n the horzontal component wth respect to known ground surveyed ponts [2]. The quanttatve assessment for the vertcal component (RMSEz) s computed based on Equaton 1 [14]. n Z RMSE Z ± 1 Z n * 2 (1) where n s the number of check ponts; s the s heght derved from LDAR DSM at control pont and s the control pont heght at the same poston on the ground. For the horzontal components, Equaton 2 wll be utlzed for dstnct or well defned ponts on the LDAR DSM and control pont such as representng the buldng edges. RMSE ( x, y) ± 2 * 2 n (X X * ) ( Y Y ) 1 n where n s the number of check ponts; X and (2) Y are the coordnates of the control ponts derved from LDAR DSM, and, are the coordnates of control ponts at the same poston on the ground. 4. Results and dscusson The result for the vertcal and horzontal component (RMSEz and RMSExy) for the evaluated dataset s shown n Table 1. Table 1. RMSEz and RMSExy for the LDAR datasets wth ground data. 5

7 8th Internatonal Symposum of the Dgtal Earth (ISDE8) RMSEz RMSExy LDAR data (± m) Referrng to Table 1, t s shown that the accuracy for the LDAR dataset n the vertcal component (RMSEz) s ± 0.09 m and t s wthn the acceptable lmt stated by the manufacturer (10-30 cm) and verfes the fndngs reported by varous researchers [4,15]. For the horzontal component (RMSExy), the accuracy estmates derved from the dataset s ± 0.31m. Referrng to the accuracy stated by the manufacturer, LDAR dataset seems to be suffcent n supportng the constructon of 3D model, both n the horzontal and vertcal specfcatons stated. However, t should be ponted out that, LDAR s desgned for the creaton of accurate dgtal surface model (heght of ground and above-surface features), the mage of features on the LDAR DSM are not dstnct to certan extent throughout the dataset. 5. Concluson The development of 3D cty model has rased great attenton n term of data sources, method to generate the 3D buldng model. The data source and 3D model generaton are the current ssues on 3D cty model development. Understandng the accuracy of the dataset n used for any applcatons s crucal, as errors propagate through processes. In ths research, the step taken towards for constructon of 3D buldng models usng Arborne LDAR datasets are shown. LDAR data have become the major sources for hgh accuracy 3D (dmensonal) dgtal models representatons. LDAR technology has been accepted n most of the mega engneerng projects n Malaysa as the technology could supply accurate Dgtal Surface Model n short delvery tme. Compared to tradtonal methods, LDAR seems to be an effectve way for terran data collecton, especally for wde area wth reasonable cost and tme consumng [10]. The ntegraton of Arborne LDAR and photographc mage s acheved nto LoD 3 n 3D buldng model development usng of Sketch Up software s contrbutes n terms of updatng the buldng model n 3D buldng model data. Meanwhle, n term of accuracy assessment, the vertcal accuracy of the derved models (LDAR data wth ground data) s ± 0.09 m whle the accuracy for the horzontal component s ± 0.31m. It s clearly shown that, the accuracy of the LDAR dataset s wthn the centmetre range as specfed by the manufacturer [2,4], whch sutable for plannng works towards creaton of 3D cty models. The prototype of 3D buldng model developed from ntegraton of Arborne LDAR technology and photographc mage can be used for mappng purpose and t has a potental to moves forward from 2D mappng nto 3D mappng. Arborne LDAR technology s an actve remote sensng and has become an effectve soluton n acqurng dense and accurate 3D data of the earth topography [16]. Acknowledgment Many thanks to the Research Intensve Fund (600-RMI/DANA 5/3/RIF (439/2012)) RMI, Unversty of Technology MARA for fundng ths research. Specal thanks to the Department of Survey and Mappng Malaysa (JUPEM) especally to all the staff at Data Acquston Secton for ther contnuous support and gudance and data provder from the Arborne Informatc Company. Research and computng facltes were made avalable by the Department of Surveyng Scence & Geomatcs. References [1] Alexander, C., Smth-Voysey, S., Jarvs, C., & Tansey, K 2009 Integratng buldng footprnts and LDAR elevaton data to classfy roof structures and vsualse buldngs. Computers, Envronment and Urban Systems [2] Lu, X Accuracy assessment of LDAR elevaton data usng survey marks. Survey Revew, [3] Idrs, R., Abd Latf, Z., Jaafar, J Accuracy Assessment of Elevaton Models Derved from LDAR. 10th Internatonal Symposum & Exhbton On Geonformaton And ISPRS 2011, Unverst Teknolog MARA, Malaysa [4] Lloyd, C. D., & Atknson, P. M Dervng ground surface dgtal elevaton models from 6

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