3d Laser Scanner and Reflectorless Total Station: a Comparative Study of the Slots of Elkhazneh at Petra in Jordan

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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: naifh@hu.edu.jo, fawwasi@excite.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...
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