Reality-based 3D modeling of the Angkorian temples using aerial images

The UNESCO world heritage site of Angkor in Cambodia houses more than 1000 historical structures within a vast area in the northern lowlands of the Tonle Sap Lake, where the Khmer empire had its center between 800 and 1327 A.D. The goal of this work was to check the possibility to derive detailed and reality-based 3D models of complex historic buildings from aerial images. JICA (Japan International Cooperation Agency) provided to the institute a block of 55 mostly black and white copies of an original set of 357 aerial photos. The images cover an area of approximately 5.3 x 5.4 km that includes the temples of Angkor Wat, Bayon and Phnom Bakheng. The average scale of the photos is 1:5100 and those displaying the main temples are in color. For photogrammetric processing, the photos were digitized with a resolution of 15 μm. For the image triangulation, geo-referencing, digital elevation model and ortho-photos generation, and for the texturing commercial and in-house programs were used. The final accuracy of image measurements achieved after the photogrammetric triangulation was σ0 = 7.3 μm. The produced Digital Terrain Model (DTM) displays a completely flat area, only interrupted by the Phnom Bakheng hill and the artificial banks surrounding the moats of the temples. For the 3D reconstruction of the temples, manual stereo measurements were performed. The resolution of the available images was not sufficient for a detailed modeling of the entire area, therefore mostly horizontal surfaces were measured and the walls were extruded to the ground. Nevertheless, one of the first 3D models of the Angkor area based on aerial images could be produced. In addition to four large temples, a variety of about 30 other structures, such as walls and modern houses, were reconstructed in 3D, the temple of Ankor Wat was taken as an example for texturing from aerial pictures.