Geodesy and Geomatics

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Browsing Geodesy and Geomatics by Subject "aerial photogrammetry"

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    Reconstruction of Digital 3D City Model Using Geomatics Technique. A Case Study in AAiT Campus of AAU
    (Addis Ababa University, 2022-06) Degu, Tadesse; Getachew, Tesfaye (PhD)
    Despite the real world we live in is considered to be represented by 3-dimension, 2D representations which neglect the third dimension were implemented to archive, plan, administer, analyze and describe the complex physical structure of the earth's surface. Thus, an extended representation technique that considers all the complexity such as 3D city modeling is emerged. A 3D city model (3DCM) is a georeferenced tridimensional digital model of the actual complex urban environment that animates all relevant urban spatial objects located above, on, or below the topographic surface integrated with their non-spatial information. The 3DCM is an important tool used in the domain of 3D cadastre, virtual reality, tridimensional spatial analyses, infrastructure planning, real-estate marketing, tourism, as well as for entertainment, and education. The 3DCM of the urban environment can be reconstructed by several technologies, the geomatics technique is there at the front of the queue. This research study is aimed to reconstruct a digital 3DCM using the geomatics technique specifically based on the photogrammetric techniques to be used as a data source as well as its data processing pipelines have been explored and tested. Thus, for this research direct georeferenced aerial photographs with aerial camera parameters with Ground control points were processed using the Inpho photogrammetry software tool that goes from automatic aerial triangulation, dense-image matching, and product generation. Thus, a photogrammetric point cloud with a density of 100 points/meter square, DTM, and a digital orthophoto map (DOM) were derived. Moreover, the accuracy of these photogrammetric products was assessed by independent checkpoints and hence obtained RMSE values in the range of a single-pixel for planimetric (x, y) dimension (aerial triangulation and DOM) and 2pixel vertical accuracy(z) that meets the standard error budget set by ASPRS for the highest accuracy geospatial data production, analysis and modeling purpose. Furthermore, File geodatabase has been developed to be used as a central data storage container and thus 2D features with their attribute information, normalized digital surface model (nDSM), DSM, DTM, DOM, and other available datasets were extracted and stored within it. From these datasets, the 3DCM at two levels of detail (LOD1 & LOD2) has been reconstructed. Consequently, this study showed that cost-effective reconstruction of 3DCM of the existing urban structure can be done from a couple of 2D nadir-looking photographs with a straightforward photogrammetric processing pipeline. The results are presented in the case of the 5kilo (AAiT) campus area of AAU.