Grid models versus TIN : geometric accuracy of multibeam data processing

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Geomatics bachelor and masters program in Belgium

A 4-year curriculum degree of Licence in Geography option Land Surveying was introduced in 1990 at two Belgian academic universities: both at the Universite de Liege in the French speaking part of Belgium and at Ghent University in the Dutch speaking part of Belgium. With the BAMA revolution in 2004, this degree has been converted into a 5-year curriculum finalised into an academic "Master in Geomatics and Surveying" (Ghent University) or a "Master in Geography, option Geomatics and Geometrology" (Universite de Liege) and subsequent "Ph.D. in Geomatics and Surveying" (Ghent University). The academic bachelor degree that gives direct access to the Master curriculum without additional compulsory courses is "Bachelor in Geography and Geomatics, Main subject: Surveying" (Ghent University), that can be obtained after 3 years of study. As suggested by the title, the geomatics/surveying degree is related to geographical sciences and located in the Faculty of Sciences. On the opposite, University Colleges (also called Technical Universities) offer professional Bachelor degrees, while academic universities only offer academic Bachelor or Master degrees. In October 2014, Ghent University will start an enhanced academic Bachelor program in Geomatics that allows direct access to the profession of chartered surveyor. The paper will discuss the education experiences, student number evolution and motivation for the enhancements of the Bachelor program

Digital representation of historical globes : methods to make 3D and pseudo-3D models of sixteenth century Mercator globes

In this paper, the construction of digital representations of a terrestrial and celestial globe will be discussed. Virtual digital (3D) models play an important role in recent research and publications on cultural heritage. The globes discussed in this paper were made by Gerardus Mercator (1512-1594) in 1541 and 1551. Four techniques for the digital representation are discussed and analysed, all using high-resolution photographs of the globes. These photographs were taken under studio conditions in order to get equal lighting and to avoid unwanted light spots. These lighting conditions are important, since the globes have a highly reflective varnish covering. Processing these images using structure from motion, georeferencing of separate scenes and the combination of the photographs with terrestrial laser scanning data results in true 3D representations of the globes. Besides, pseudo-3D models of these globes were generated using dynamic imaging, which is an extensively used technique for visualisations over the Internet. The four techniques and the consequent results are compared on geometric and radiometric quality, with a special focus on their usefulness for distribution and visualisation during an exhibition in honour of the five hundredth birthday of Gerardus Mercator

Photogrammetric restitution of a presumed ancient Asclepius temple in Titani, Peloponnesos, Greece

Close range photogrammetry is a useful tool for the documentation and registration of archaeological sites. In this case, photogrammetric restitution is applied to a presumed Esclepion Classical temple site in Titani, Peloponnesos, Greece. The archaeological remains that are recorded and processed in this stage are small fragments of walls, made out of irregular shaped stones. The fragmentary remains and the need to record both the facades of the stones as well as the upper surfaces, complicate the photogrammetric recording and processing workflow. The use of 3D documentation is important for the documentation, conservation and possible further excavation of the site. Stereographic pictures in combination with terrestrial topographic measurements are processed in the photogrammetric software VirtuoZoTM. The stereo photographs were taken by a non-metric high resolution digital single lens reflex camera with a minimum overlap of 65 percent. Targets placed on the remains of the walls were measured by total station to obtain ground control points for the orientation of each 3D stereo model in an absolute coordinate system (HGRS87). The photogrammetric processing of the stereo models results in very accurate digital elevation models and orthophotos of the walls. Further combining of these final products and merging these products in a CAD software leads to a 3D presentation of the archaeological excavation, which can be further used to evolve this archaeological site

Classification of airborne laser scanning point clouds based on binomial logistic regression analysis

This article presents a newly developed procedure for the classification of airborne laser scanning (ALS) point clouds, based on binomial logistic regression analysis. By using a feature space containing a large number of adaptable geometrical parameters, this new procedure can be applied to point clouds covering different types of topography and variable point densities. Besides, the procedure can be adapted to different user requirements. A binomial logistic model is estimated for all a priori defined classes, using a training set of manually classified points. For each point, a value is calculated defining the probability that this point belongs to a certain class. The class with the highest probability will be used for the final point classification. Besides, the use of statistical methods enables a thorough model evaluation by the implementation of well-founded inference criteria. If necessary, the interpretation of these inference analyses also enables the possible definition of more sub-classes. The use of a large number of geometrical parameters is an important advantage of this procedure in comparison with current classification algorithms. It allows more user modifications for the large variety of types of ALS point clouds, while still achieving comparable classification results. It is indeed possible to evaluate parameters as degrees of freedom and remove or add parameters as a function of the type of study area. The performance of this procedure is successfully demonstrated by classifying two different ALS point sets from an urban and a rural area. Moreover, the potential of the proposed classification procedure is explored for terrestrial data