XXI International CIPA Symposium, 01-06 October, Athens, Greece
3D Laser Scanner and Reflectorless Total Station: A Comparative Study of the Slots of ElKhazneh at Petra in Jordan Naif Haddad, Fawwas Ishakat
Department of Conservation Science, Queen Rania Institute of Tourism and Heritage, the Hashemite University, Zarqa 13115, Jordan. E-mail: firstname.lastname@example.org, email@example.com Key Words: Compression, Laser scanning, Application, Accuracy, Point Cloud, Surveying, Acquisition, Processing. ABSTRACT Today, the laser scanners are widely used in the field of architectural, archaeological and environmental surveying because of their practicality and flexibility. A laser scanning machine can be considered as a high automation reflectorless total station; by means of a laser based measurement of distance and accurate angular movement, a target object is sampled in a regular mesh of 3D points. To achieve a real comparison between the technical qualities of the laser scanning machine and reflectorless total station, the case of a high slots and in a vertical position, had been chosen at El-Khazneh (the treasury) at Petra in Jordan, where the use of traditional measuring methods, if not impossible, at least are very difficult to achieve. These slots are located in an inaccessible place beside ElKhazneh, on both the right and the left side. Until now there are no satisfactory measurements of those slots. There are two rows of approximately square holes. The problem of how to choose the viewpoint positions and the time represents important factors of the survey for those slots where the mountainous environment surrounding El-Khazneh restricts potential sensor stations. To overcome this problem and to achieve precise measurements of those slots, we used a 3D laser scanner (Mensi GS 100) to build a 3D mesh model, and a modern reflector-less total station (Leica), which has the ability to use a visible laser beam. The two techniques, the problems and difficulties that arose during the survey process are shown in the paper. The obtained result of these two techniques will be discussed and evaluated. 1. INTRODUCTION A surveyor collecting data using pre-electronic techniques could have used the tape to take the measurements, together with a cross section for elevation information and quantity estimates, or the survey could have been completed using such polar techniques as transit or theodolite / EDM surveys. In fact, cultural heritage documentation frequently requires integrating survey data from different sources. Currently, the preferred way to achieve this goal is through an integrated use of different documentation technologies. Actually, partitioning processes and integration of different measurement and modeling techniques appear to be useful in cultural heritage documentation and representation. As a general rule, the greater the accuracy required the more time and money will be required to achieve it. However, a laser scanning machine can be considered as a high automation reflectorless total station; by means of a laser based measurement of distance and accurate angular movement, a target object is sampled in a regular mesh of 3D points. Meanwhile the objects that can be documented range from the sizes of coins or potsherds to whole cultural landscapes. To achieve a real comparison between the technical qualities of the laser scanning machine and reflectorless total station, the case of a high slots and in a vertical position, had been chosen at El-Khazneh (the treasury) at Petra in Jordan, where the use of traditional measuring methods, if not impossible, at least are very difficult to achieve. 2. EL-KHAZNEH OF PETRA AND THE SLOTS The architecture of Petra reflects the spirit of the Hellenistic and Roman period, where architects moved among different cultures to create high artistic standards in architecture in cooperation with the local tradition in order to achieve a new approach to the stylistic aspect. Thus, the façades are...
References: -Agosto, E., Ardissone, P. and Bornaz, L., The Castle Of Graines: Different Survey Methodologies For The Documentation Of Historical Buildings, CIPA, XX, Torino, Italy, Vol. 1, 2005, 55-58. -Boehler, W., Heinz, G. and Marbs, A., The potential of noncontact close range laser scanners for cultural heritage recording, In: CIPA, Working group VI, 2001, 431-436. -McKenzie, J. (1990). The Architecture of Petra. Oxford: Oxford University Press. -Parr, P. (1968). “The Investigation of Some ‘inaccessible’ Rock-cut Chambers at Petra”. PEQ 100: 5-16. -Rababeh, Sh. M., 2005, How Petra was Built: An analysis of the construction techniques of the Nabataean freestanding buildings and rock-cut monuments in Petra, Jordan, The Basingstoke Press , Oxford.(dissertation).
Table 3 Measurement recorded using reflectorless Total station of the right side slots of the El-Khazneh.
measurement recorded using 3D Laser scanner Slot ID 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 a 200 240 180 170 230 210 260 250 237 280 300 260 340 413 345 257 256 277 220 271 220 350 273 330 300 235 b 120 120 220 225 332 265 290 293 260 294 242 280 266 257 243 298 370 363 394 340 375 260 402 420 440 220 c 180 230 190 164 240 210 267 300 277 350 320 310 330 359 315 270 301 272 247 285 275 340 247 370 291 370 d 125 140 297 220 328 282 254 290 302 298 212 300 287 319 278 325 337 364 382 334 316 400 490 369 449 110 e 90 90 120 85 120 100 110 118 110 140 90 80 130 95 90 100 90 80 120 140 90 90
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