1,721,072 research outputs found
Integrated techniques for low-cost surveying of urban areas
No full textThis paper deals with the purpose of a methodology integrating different surveying techniques to efficiently produce a large-scale digital mapping of urban areas. At first, a comparison among methods for reuse/updating of existing maps, aerial modern techniques and terrestrial ones is carried out, highlighting the pros/cons characterizing each one and in the attempt to find the “best technique” as well a suitable
integration/synergism among them. The integration herewith adopted considers the availability of a 3D-vector numerical mapping and the photogrammetric exploiting of images acquired either (dynamically) by a low-cost MMS or (statically) by a non-metric high-resolution CCD. MMS allows the survey of 3D-control points for the successive processing of the CCD images. Afterwards for such techniques, the global work strategy and the different analytical model applied are explained. The main features of the algorithm for MMS data processing are: a direct/indirect orientation model, the stochastic prediction of point coordinates, and a pseudo-dynamic solution approach. Moreover, the analytical model of photogrammetric use of CCD images takes into account the inauspicious errors due to MMS survey by means of suitable techniques for stochastic prediction of unknowns. At the paper end, the promising results obtained from an application on real data of this integrated method are shown and evaluated
Road survey by Kalman filter rectification of image sequences acquired with a monoscopic low-cost MMS
No full textThis paper proposes a method for a mosaic digital representation of a road by means of a Kalman filter based rectification of a
monoscopic image sequence acquired with a low-cost MMS without INS sensors. The frontal images of the road acquired by a pointing ahead-down camera are rectified onto the road surface by means of a homographic transformation among image and ground TIN planes. As basic idea, the “external/homographic” image parameters constitute the unknown “state vector” of a Kalman filter pseudo-dynamic model, describing its evolution with respect to the covered distance, with observation equations given from image coplanarity and collinearity conditions and GPS kinematic measures. To make easy the relative orientation among images, an
original Kalman filter image matching is exploited: once selected some lane tract points in the “first” image, the homologous points in the “second” image are so automatically detected. Exploiting only near points in the lower part of the images, a high-scale optical
model with a strong geometrical consistency is achieved: therefore, a reliable rectification of the image sequence can be expected. This method has been implemented in a Matlab language program making possible the rectification of the image sequence by a digital resampling with automatic mosaicking onto TIN finite planes modeling the road surface. First numerical experiments with real data of our MMS prototype have given satisfactory results here described and analyzed
Lis Termis Romanis e la Basiliche Patriarcjâl di Aquilee studiadis midiant lis modernis tecnichis di rilevament e di rapresentazion / The Roman Thermae and the Patriarchal Basilica of Aquileia analyzed by modern techniques of surveying and representation
No full textThe paper deals with the analysis of the Roman Thermae and of the Patriarchal
Basilica of Aquileia by means of the modern techniques of laser scanning and photogrammetric surveying and of representation. As a preliminary Introduction, the noteworthy history of Aquileia is just briefly recalled, as well as that of the Great Roman Thermae, nowadays an area of archaeological excavations, and of the Patriarchal Basilica, one of the most significant monuments of Italian Romanesque architecture. The following Materials and methods chapter is focused, after the explanation of how laser scanning functions, then the various operative steps to automatically acquire independent clouds of millions of 3D points, transform them into a geo-referenced colour textured unique 3D surface, and represent it in many different digital views.
Then, in the Results the practical surveying and representation application of the two Aquileia sites is shown, mentioning the full automation of the data acquisition in the field and the impressiveness of the data processing and the digital representations carried out with dedicated software. In the Discussion, the experience gained from the Aquileia cases and future projects are discussed, mainly concentrating on key-points of the level of automation attainable in the data processing
Dynamic models for the external orientation of a “Mobile Mapping System”
No full textThe paper deals with the advanced technique for terrestrial survey realised by means the so-called "Mobile Mapping Systems" (MMS), costituted by a vehicle equipped with satellite, inertial and imaging sensors. In a first part, the geometrical model currently applied for the MMS survey is described, with particular emphasis to the practical advantages of the sensor integration, carried out by using dynamic models chich also assuring a computational optimisation. In the other part, as alternative geometrical model is proposed which uses instead photogrammetric observations for the imaging sensor eternal orientation: the problem datum can be fixed by using the absolute coordinates of some image-points, e.g. stored in a digital mapping. For such end, particular state vector and matrix transition of the dynamic model are chosen by following analytical motivations here described
A Kalman filter based matching for a MMS image sequence
No full textThis paper proposes an original image-matching algorithm for consecutive digital images acquired by means of the CCD sensor of a Mobile Mapping System (MMS). For such end, once a point is (manually) chosen in the “first” image, a Kalman filter based
model is applied to automatically search for the homologous point in the “second” image. The matching geometric parameters are given from the six coefficients of the affine transformation from the template to the patch window, while the radiometric parameters are the two coefficients of the linear radiometric transformation between the same windows. The usual “Least Squares Matching” condition between template/patch grey-values is applied. To improve the solution convergence, the geometrical constraint given by the well known “epipolar line” (in the second image) is employed. This line comes out from the so-called “coplanarity condition” between homologous image points. The epipolar line equation makes possible to analytically define the filter “geometrical state equation”. This is possible since, while usually as “state vector” an unknown dynamic quantity is utilised, a simplest unknown geometric quantity, suitably defined, is now employed. An iterative solution strategy is carried out in recursive steps until the convergence is fulfilled.
The implementation/experimentation of the matching model is now in progress, by using MATLAB software, and it is giving well promising numerical results
La georeferenziazione diretta dei sensori per il rilevamento: aspetti metodologici ed analitici
No full textThis paper deals with methodological and analytical topics of the external orientation (georeferencing) of surveying sensors, achievable nowadays directly by “on board” GPS/INS measures,
eventually integrated by other kinds of available data. In the first part, the geometrical aspects are illustrated (sequence of 3D roto-translations among reference frames) and a pros/cons comparison between indirect and direct methods is carried out.
The analytical aspects involve the stochastic prediction by means of Kalman filter dynamic model, widely applied in Mobile Mapping System (MMS) field to efficiently solve surveying problems. The experimental application of own pseudo-dynamic algorithm on OEEPE Test “Integrated Sensor Orientation” GPS/INS and imaging aerial data has given well results finally presented
Esperienze di modellazione 3D da scansione laser di beni architettonici del Friuli Venezia Giulia
No full textHere are presented three different experiences of 3D modeling carried out from terrestrial laser scans relating to three Friuli Venezia Giulia architectural heritages which significantly different for size and for surveying conditions. These are the long medieval walls of Venzone, the great facade of the Lombard-Romanesque Cathedral of Gemona of Friuli and the War Memorial to the “Brigata Udine” subdivided into eleven parts located in the lapidary of Udine. After explained the motivation of this paper, the attention is focused on the operating conditions common for the three case studies, that is the use of Riegl Z390i integrated with a Nikon D200 metric camera and the RiSCAN PRO software. After that, the three cases are presented separately, first with a brief description of the object of the survey/modeling, and then discussing with greater detail the steps of the data acquisition and those relating to the various processing performed, focusing on encountered problems, identified solutions and obtained results. Finally a comparison among the three experiences is done, from which, as espected, similarities of differences come out: 3D modeling is anyway a process that, starting from the same acquired data, is not univocal and therefore the experience is a key factor to accomplish the best result
Un algoritmo per il matching dinamico in un sistema di rilevamento multi-sensore
No full textL'articolo propone un algoritmo originale per la soluzione dinamica del matching fra immagine successive acquisite con una camera digitale (CCD) posta a bordo di un sistema di rilevamento terrestre multi-sensore (Mobile Mapping System, MMS)
Il rilievo fotogrammetrico di una chiesa del ‘500
No full textLa procedura fotogrammetrica del raddrizzamento digitale rappresenta oggigiorno uno strumento affidabile e ad alta produttività per il rilievo di elementi architettonici a costi contenuti e non richiede conoscenze fotogrammetriche e topografiche particolarmente approfondite. Il prodotto informatico così realizzato rappresenta uno strumento conoscitivodi notevole utilità per una corretta progettazione e gestione dell'intervento di restauro del bene architettonico preso in istudio
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