ANALYSIS OF WALLS AND PILLARS OF THE HYPOSTYLE HALL AT THE QH31 TOMB (ASWAN, EGYPT) BASED ON 3D MODELS

This study describes the methodology developed and the results obtained about the geometric behaviour of walls and pillars of one of the most prominent rock-cut funerary structures of the Middle Kingdom period located in the Necropolis of Qubbet el-Hawa. More specifically, we selected the hypostyle hall of the QH31 hypogeum, one of the greatest in the Necropolis, to apply this methodology. The main objective is related to obtaining geometrical aspects of walls and pillars in order to understand the constructive procedure carried out almost four millennia ago. The methodology was based on photogrammetric and TLS surveys that allowed us to obtain a complete combined 3D model of the structure, geometrically contrasted and with real texture. From this product we obtained a high density point cloud, where some planes were fitted considering the walls and pillars that defined the structure. These planes were characterized by their normal vectors, which were used to analyse several geometric aspects such as inclinations, parallelism and perpendicularity. As results, we have obtained important information about the level of accuracy of the constructive procedure carried out by the ancient Egyptians. In this sense, the values obtained allow us to suggest and confirm several hypotheses about the construction of this hypogeum. The proposed methodology has demonstrated its feasibility for determining these geometric aspects of funerary structures through the analysis of the fitted planes obtained from the 3D model

COMPARISON OF LOW ALTITUDE PHOTOGRAMMETRIC METHODS FOR OBTAINING DEMS AND ORTHOIMAGES OF ARCHAEOLOGICAL SITES

In this work it is performed a comparison of two methods for obtaining digital elevation models (DEMs) and orthoimages of medium-sized archaeological sites (500-5000 m2). The photogrammetric methods analyzed consist in the use of a light aerial platform applying the normal case of photogrammetry (vertical photographs and regular blocks), and the second one is based on a network of oblique photographs, taken from a telescopic mast, using a DEM obtained from a terrestrial laser scanner (TLS) survey. The main goal is to analyze the more efficient method for these studies taking into account variables such the working time, the accuracy obtained in the final products, the visual analysis of final orthoimages, etc. This study has been applied to the same archaeological site in two different epochs. The image acquisition was performed before and after a conservation intervention at the archaeological site. The results have shown similar characteristics for both products (DEMs and orthoimages) and accuracies but the density of DEMs and the visual analysis of orthoimages have shown differences that allows us to select the more adequate method taking into account the characteristics of each case. Thus the DEMs obtained using the TLS survey has shown more density of points while the visual analysis of orthoimages has shown a better behaviour (radiometrically and visually) in the case of vertical photographs

ANALYSIS OF LANDSLIDES BASED ON DISPLACEMENTS OF LINES

Nowadays, the development of UAS has allowed the obtaining of high resolution and accurate cartographic products, such as DSMs and orthoimages. These products can be used in studies of the evolution of landslides. The stability of slopes is a main issue because, among others, it can suppose a serious risk to infrastructures. Until this moment, some studies for analysing slope movements have been carried out using the comparison of positions of well-defined points or comparing two surfaces obtained from two DSMs. In this paper we present a methodology for analysing landslides based on some linear elements located on the terrain. More specifically, we analyse some lines of road sections which are located on an unstable slope, checking the movements of the landslide and their effect on the infrastructure. The methodology includes the obtaining of high resolution orthoimages and DSMs which correspond to two or more epochs of the same landslide, the 3D digitizing of common linear elements, and the computing of the displacements of matched lines (from two epochs) using positional control methods based on lines. The proposed methodology has been tested using two DSMs and two orthoimages (corresponding to two epochs) obtained from two photogrammetric projects developed with an UAS. This real case was applied to an unstable slope with landslides which affected several sections of a road. The results have demonstrated the viability of the proposed methodology in analysing the behaviour of the landslide and more specifically, the effects on these infrastructures

METHODOLOGY FOR ORIENTATION AND FUSION OF PHOTOGRAMMETRIC AND LIDARDATAS FOR MULTITEMPORAL STUDIES

Nowadays, data fusion is one of the trends in geomatics sciences, due to the necessity of merging data from different kind of sensors and periods of time. Also, to extrract the maximum information from data and useful multitemporal analysis, an exact geoconnection of all datasets in a common and stable reference system is essential. The results of the application of a methodology for an integrated orientation into a common reference system using data obtained by LiDAR systems, digital and historical photogrammetric flights dataset, used for proper analysis in multitemporal studies, are presented in this paper. In order to analyse the results of the presented methodology, several photogrammetric datasets have been used. This data corresponds with digital and analogic data. The most current flight (2010) combines data obtained with digital photogrammetric camera and LiDAR sensor which will be used as reference model for all subsequent photogrammetry flights. The philosophy of the methodology consists of orientating all photogrammetric flights to the DEM obtained by LiDAR data. All the models obtained from every photogrammetric block are comparable in terms of the geometric resolution of each one. For that reason, altimetric stable points are extracted automatically from the LiDAR points cloud to use these points such as altimetric control point in the different flights that must be oriented. Using LiDAR control points, we demonstrate the improvement in the results between initial orientation and final results. Also it is possible to improve the planimetric correspondence between different photogrammetric blocks using only altimetric control points iteratively