Digital Softcopy Photogrammetry

Transcription

1 LLP Erasmus IP EPOCHE 2013 Thassos Island, Greece, 2-16 June 2013 Digital Softcopy Photogrammetry Prof. Levente DIMEN The 1 Decembrie 1918 University of Alba Iulia, Romania

2 GENERAL CONTEXT In the last years, in Romania the urban population (Figure 1) has reached a stage of 55%, this leading to the necessity of spatial system designing. Figure 1. Internal migration of Romania s population based on age groups Data from Statistics National Institute of Romania shows that urban areas are becoming more and more populated (Figure 2 and 3). Thus, as information changes continuously in time and space, the decision makers have to find solutions for improved planning in order to maintain community services at a high level and stimulate change and development. Figure 2. Migration of the population to urban areas in 2009 Figure 3. Classification of Romania s counties based on population s preference for urban areas

3 LOCATION OF THE AREA UNDER STUDY Timişoara municipality (Figure 4) is among the first cities in Romania to develop a general project for urban planning. Figure 4. Location of Timişoara municipality in Romania The urban GIS of Timişoara was implemented in 1998 having the main purpose of ensuring a balanced development of the city and controlling its urban sprawl. It also enabled an efficient communication between state agencies, local administration departments, the private sector and the academic environment that would ensure a complete, updated and professional picture of the real situation (Figure 5). Figure 5. Extract from the Urban GIS of Timişoara In the process of updating this complex project and compiling the digital plan, an important task is represented by data acquisition, data processing and storage of all information related to historical monuments, architectural and urban development inventory from Timişoara municipality.

4 TECHNOLOGIES AND METHODS In the last decade, remarkable increase has occurred in the demand for 3D models for cultural heritage applications. The techniques employed have evolved from surveying and CAD tools and/or traditional photogrammetry into laser scanning and more automated image-based techniques. However, in some cases one technique does not always give the most precise results, thus the need for complementary studies appeared. A highly detailed structure or site is best modeled at various levels of detail. Image-based modeling is used for the basic shape and structural elements, and high precision laser scanning for fine details and sculpted surfaces. To present the site in its proper context, image based rendering or panorama is useful for landscapes and surroundings. The most obvious motives for 3D modeling of heritage sites are documenting historic buildings and monuments for reconstruction or restoration if they are destroyed, and creating education resources for history and culture students and researchers. Other motives include visualization from viewpoints that are impossible in real world due to size or accessibility, interaction with objects without risk of damage and virtual tourism. Most applications specify a number of requirements, mainly: high geometric accuracy, capturing all details, and photorealism. Other desirable features include full automation, low cost, portability, and optimum model size (Figure 6). Image based approaches entail widely available hardware (professional digital cameras) and potentially the same system can be used for a broad range of objects and scenes. They are also capable of producing realistic looking models and those based on photogrammetry have high geometric accuracy. The issues that remain in image-based modeling are the capture of details on unmarked and sculpted surfaces and the full automatic creation of the 3D models. Imagebased rendering does not need a geometric model and it can be applied for virtual tourism. Figure 6. Textured model of a 3D building facade with image rectification [A case study on the historical peninsula of Istanbul based on three-dimensional modeling by using photogrammetry and terrestrial laser scanning Bahadir Ergun, Cumhur Sahin, Ibrahim Baz, Taner Ustuntas, Environmental Monitoring and Assessment (2010) 165: , DOI /s ]

5 THE PROPOSED STUDY CASES The University aims at using this technology in order to obtain new data that should be inserted in the described urban GIS thus contributing to the updating conception of the urban GIS database for Timişoara municipality, using knowledge from different sources of cadastre, photogrammetry and GIS. We already have the possibility to obtain ground coordinates by means of ground surveys. The target group must learn from this experience how to effect the geometric calibration of the digital cameras in order to calculate the needed parameters. The specialty literature has already shown that commercial digital SLR cameras are suitable for a detailed 3D evaluation and reconstruction of large, complex historical buildings. Due to the digital data flow, architectural photogrammetry has now become an efficient alternative to the classical building measurement and reconstruction methods [Kersten 2004]. The methodologies that will be used for 3D modeling include entirely professional and conventional studies of orientation, evolution, and drawing, in which geodetic and photogrammetric techniques will benefit. After the geodetic geo-registering studies, the process, which will be based on taking terrestrial photogrammetric images of objects or providing satellite images, is going to be initiated and then it will finalize by generating the base maps that are used for creating 3D surface models, 3D geo-referencing of their details, and generating 3D urban model (Figures 7 and 8). Apartment buildings School building Figure 7. View from Timişoara

6 Historical building Opera house Figure 8. Opera Square in Timişoara Timişoara is only a few steps away from creating a virtual 3D city model, which has become increasingly popular in recent years as it supports urban planning and decision making processes, and the participation of our staff and students to this project is an important step towards it becoming reality, towards the reaching of that goal.