290 research outputs found

    The demand for hydrographic surveyors in the Benelux

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    In February 2015, the Hydrographic Society Benelux (HSB) sent an extended questionnaire to 77 of the most important hydrographic companies in the Benelux (Belgium, The Netherlands and Luxemburg). The organization of this questioning was in cooperation with the Department of Geography of Ghent University (Belgium). The purpose was to inquire the demand for hydrographic surveyors during the next 5 years in the Benelux. The Benelux is hosting the four biggest dredging companies in the world, so the demand for hydrographic surveyors is usually fairly high and a good parameter for the general demand in the West of Europe. On the one hand, the aim of the questionnaire was to research the demand for the preferred level of hydrographic surveyor, allowing a concise estimation of the demand for IHO category-A and category-B certified hydrographic surveyors. On the other hand, the required balance between hydrographic surveyors with a Bachelor versus Master degree was questioned. As a similar questionnaire and analysis has been performed in 2009, trends over the past 6 years can be discerned and analyzed. The results are important, not only for the private companies, but also for the higher education institutes. In the Benelux, but also outside the Benelux, one can find hydrographic institutes delivering cat. A and cat. B. IHO certified hydrographic surveyors, combined or not with a Bachelor and/or Master diploma. It is generally assumed that there is a shortage of hydrographic surveyors and/or of hydrographical educated employees in the Benelux. Currently, part of the active hydrographic surveyors in the Benelux are engineers, geologists and other non-specifically hydrographic trained people, who received additional bathymetric trining within private companies. But does this hypothesis withstands a scientific analysis? This will be critically analyzed in this paper

    Geomatics bachelor and masters program in Belgium

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    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

    Applied surveying education : documenting cultural heritage in 3D in the city of Ghent (Belgium) using laser scanning and photo modelling

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    For several years the city of Ghent (Belgium) and the Ghent University, Department of Geography have been working together to document and measure important cultural heritage sites in 3D. The partnership enables master students in Geomatics and Surveying at the Ghent University to take part in a project driven measuring campaign. During the project, students use and compare several 3D data acquisition methods. This allows the students to implement their theoretical knowledge in the field. The used methods are analysed and critically compared by the students. Through this hands-on-training, students are encouraged to think “outside the box”. When problems occur, they are stimulated to think how these problems could have happened and most importantly how they can solve them. The documentation of these historic monuments in Ghent will be used during future renovation works and archaeological research. This paper will discuss the measurements in the Ghent City Museum (Stadsmuseum or STAM). The following methods are applied during the extensive field work: engineering surveying using total station and GNSS, photo modelling and laser scanning. The deliverables are created in a CAD or GIS environment. After successful completion of the course, students have gained a significant expertise concerning the processing of topographic data, 3D point clouds and imagery in an integrated way. This knowledge can be used after their studies to assess which equipment is most suitable for any given survey project. The final products of the photo modelling and the laser scanning process is a 3D model. Furthermore, digital elevation models and orthorectified images of the historic monument can be created. The orthorectified images are visualised and processed into high resolution orthophoto plans, in a CAD or GIS environment

    The use of high resolution digital surface models for change detection and viewshed analysis in the area around the pyramids of Giza, Egypt

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    One of the biggest threats to cultural heritage is related to their rapidly changing and developing surroundings. The Giza pyramid plateau is a prime example of this phenomenon, as it is threatened by the enormous urban expansion of Cairo over the last decades. Documenting, monitoring and modelling such a pressure requires accurate and detailed geographic data, which can be derived from recent up-to-date, high resolution satellite images. Remote sensing techniques have proven to be very useful to visualize and analyze urban sprawl and land use changes in two dimensions. The impact assessment of urban sprawl near specific heritage sites, however; needs to be complemented with accurate 2.5D-information. In an attempt to do so, digital surface models (DSMs) from Ikonos-2 (2005) and GeoEye-1 stereoscopic images (2009 and 2011) have been computed in order to analyze recent urban changes. Change detection methods are mainly developed for large scale high resolution aerial images; however this paper focuses on the one hand DSM creation and its challenges resulting in an improvement of 2.5D change detection method for small scale satellite imagery in mainly informal areas. On the other hand a view shed evolution is presented. The combination of the enhanced digital terrain extraction (eATE) module of Erdas Imagine® and ground control points collected in the field provides accurate and high resolution DSMs. The impact of shadow and different urban morphologies however influence the pixel-wise comparison of the two DSMs, which results in different approaches for different city districts. The resulting 2.5D change model clarifies not only the urban sprawl, but also the increase in building levels, directly related to pressure on the famous pyramids. This pressure is furthermore analyzed by creating different view sheds through time from the plateau towards the city and vice versa. An integration of population statistics complements the model, hence allowing it to become a useful policy instrument

    Airborne photogrammetry and LIDAR for DSM extraction and 3D change detection over an urban area : a comparative study

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    A digital surface model (DSM) extracted from stereoscopic aerial images, acquired in March 2000, is compared with a DSM derived from airborne light detection and ranging (lidar) data collected in July 2009. Three densely built-up study areas in the city centre of Ghent, Belgium, are selected, each covering approximately 0.4 km(2). The surface models, generated from the two different 3D acquisition methods, are compared qualitatively and quantitatively as to what extent they are suitable in modelling an urban environment, in particular for the 3D reconstruction of buildings. Then the data sets, which are acquired at two different epochs t(1) and t(2), are investigated as to what extent 3D (building) changes can be detected and modelled over the time interval. A difference model, generated by pixel-wise subtracting of both DSMs, indicates changes in elevation. Filters are proposed to differentiate 'real' building changes from false alarms provoked by model noise, outliers, vegetation, etc. A final 3D building change model maps all destructed and newly constructed buildings within the time interval t(2) - t(1). Based on the change model, the surface and volume of the building changes can be quantified

    Macrotidal beach monitoring (Belgium) using hypertemporal terrestrial lidar

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    Macrotidal Beach Monitoring (Belgium) using Hypertemporal Terrestrial Lidar Greet DERUYTER, Lars De SLOOVER, Jeffrey VERBEURGT, Alain DE WULF, Belgium and Sander VOS, the NetherlandsKey words: Continuous Terrestrial Laser Scanning, Coastal Monitoring, Beach Mapping, North SeaSUMMARY In order to protect the Belgian coast, knowledge on natural sand dynamics is essential. Monitoring sand dynamics is commonly done through sediment budget analysis, which relies on determining the volumes of sediment added or removed from the coastal system. These volumetrics require precise and accurate 3D data of the terrain on different time stamps. Earlier research states the potential of permanent long-range terrestrial laser scanning for continuous monitoring of coastal dynamics. For this paper, this methodology wasimplemented at an ultradissipative macrotidal North Sea beach in Mariakerke (Ostend, Belgium). A Riegl VZ-2000 LiDAR, mounted on a 42 m high building, scanned the intertidal and dry beach in a test zone of ca. 200 m wide on an hourly basis over a time period of one year.It appeared that the laser scanner could notbe assumed to have a fixed zenith for each hourly scan. The scanner compensator measured a variable deviation of the Z-axis of more than 3.00 mrad. This resultedin a deviation of ca. 900 mm near the low water line. A robust calibration procedure was developed to correct the deviations of the Z-axis. In this paper, we start by presenting the first results achieved with the current methodology. Next, we analyze the results from a 10-day measurement campaignand highlight the tide-dominated beach morphology

    Determining geometric primitives for a 3D GIS : easy as 1D, 2D, 3D?

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    Acquisition techniques such as photo modelling, using SfM-MVS algorithms, are being applied increasingly in several fields of research and render highly realistic and accurate 3D models. Nowadays, these 3D models are mainly deployed for documentation purposes. As these data generally encompass spatial data, the development of a 3D GIS would allow researchers to use these 3D models to their full extent. Such a GIS would allow a more elaborate analysis of these 3D models and thus support the comprehension of the objects that the features in the model represent. One of the first issues that has to be tackled in order to make the resulting 3D models compatible for implementation in a 3D GIS is the choice of a certain geometric primitive to spatially represent the input data. The chosen geometric primitive will not only influence the visualisation of the data, but also the way in which the data can be stored, exchanged, manipulated, queried and understood. Geometric primitives can be one-, two- and three-dimensional. By adding an extra dimension, the complexity of the data increases, but the user is allowed to understand the original situation more intuitively. This research paper tries to give an initial analysis of 1D, 2D and 3D primitives in the framework of the integration of SfM-MVS based 3D models in a 3D GIS
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