Yahya Alshawabkeh

Combining laser scanning and photogrammetry: a hybrid approach for heritage documentation

High quality 3D models of cultural heritage sites can be generated efficiently by laser scanning, which allows the accurate and dense measurement of surface geometry. In addition to the geometric data collection, texture mapping based on additionally collected digital imagery is particular important for this type of application. This requires a combined processing of range and image data sets. For this purpose, they have to be registered or aligned by a suitable transformation to a common reference coordinate system. The involved transformation parameters can be determined based on corresponding elements to be extracted from the different data sets. In the paper an efficient edge detection algorithm is presented, which allows for the automatic segmentation of such primitives even in complex scenes. In order to achieve a high quality 3D photo-realistic mode,l this alignment process has to be followed by an automatic texture mapping, which is discussed in the second part of the paper. The presented algorithms are demonstrated in the framework of a project aiming at the generation of a 3D virtual model of the Al-Khasneh, a well-known monument in Petra, and a Roman Theatre in ancient Jerash city, Jordan.

3D Digital Documentation, Assessment, and Damage Quantifi cation of the Al-Deir Monument in the Ancient City of Petra, Jordan

Abstract The rock-cut monuments in the ancient city of Petra in Jordan form an outstanding tangible heritage site. Unfortunately, this important part of the worlds cultural heritage is gradually being diminished due to weathering and erosion problems. In this research, an approach combining in situ surveying and laboratory analysis is applied in order to provide sufficient and comprehensive data regarding the documentation and evaluation of the status of the Al-Deir monument in Petra. The purpose was not only to quantify the damage, but also to make a first step towards creating a 3D monitoring programme of the deterioration rate. The approach presents a correlation study between the environmental condition and the surface weathering damage, using 2D mapping of the weathering form and accurate 3D realistic modelling from laser scanning and digital photogrammetry. The 2D mapping provides detailed weathering damage information for the entire stone surface of the monument, whereas the 3D modelling provides information on the spatial distribution and texture of the damage. Additionally, the 3D digital model can provide reference data as an exact guide to the restoration needed. In order to support the visual presentation of 3D surface details, a hybrid approach combining data from laser scanning and digital imagery was developed. Studies of stone texture and spatial distribution of soluble salts were carried out at the monument in order to explain the mechanism of the weathering problem. Relative humidity, temperature, and wind are the main factors in the salt damage process. In order to study the effect of these conditions in the salt crystallization process a series of fieldwork investigations and laboratory work were undertaken. The results show that visible zoning of weathering damage is correlated to different salt concentrations.

An enthroned Tyche statue from Gadara / Umm Qais, Jordan

The round statue of enthroned Tyche was originally displayed in the middle of the front row of seats in the west theatre of Umm Qais. The statue of high quality is made of ivory coloured marble, while the theatre is constructed of black basalt stone. This contrast of colour and material made the statue stand out and intensified the beauty of the theatre. The statue has been moved by the Department of Antiquities of Jordan and displayed at Umm Qais Archaeological Museum, registered as number 13c. The Gadara Tyche appeared with one of the main symbols of the goddess, the cornucopia. Highly realistic and geometric models of cultural heritage objects are attractive tools for documentation, preservation and promotion purposes. 3D imaging, using dense stereo matching techniques, is used for accurate and realistic modeling of the Tyche statue and the theatre of Umm Qais. Acquiring 3D surfaces with image matching solutions has many advantages related to the flexibility, cost effectiveness of, and need for short data collection time on the site without disturbance to the site’s visitors.