1,721,063 research outputs found
The hierarchic concept of the geodetic network in the GPS era: one example in the Friuli-Venezia Giulia region
No full textAspetti analitici connessi alla realizzazione di un sistema di rilevamento topografico dinamico
No full textOltre la misura – Cronistoria e obiettivi delle spedizioni scientifiche che hanno effettuato la rideterminazione geodetica delle quote dell’Everest e K2
No full text
Metodo per effettuare la triangolazione aerea
No full textMetodo per effettuare una triangolazione aerea basandosi su tecniche applicate all'analisi procustiana in cui ogni sua fase è il risultato di connessioni topologiche tra gli insiemi numerici e di operazioni geometriche elementari effettuate sugli insiemi di dati, per cui tali operazioni determinano un bassissimo impatto computazionale ed algebrico
Definizione automatica da rilievi lidar di attributi geometrici per il GIS 3D urbano
No full textSi descrive una procedura per aggiornare ed estendere un SIT 2D urbano esistente, ricavando mediante l’uso di funzioni disponibili in ambiente GIS, attributi geometrici 3D di interesse
urbanistico, desumendoli in modo automatico da rilievi LiDAR opportunamente classificati.
Si illustra inoltre come sul dato LiDAR si possa costruire un supporto tridimensionale, il 3D city model, da integrare al SIT 2D, che permetta di navigare in un ambiente virtuale e di interrogare la banca dati aggiornata selezionando oggetti 3D
A Generalized Factored Stochastic Model for Optimal Registration of LIDAR Range Images
No full textSurveying complex shapes or very large entities by laser scanners often requires the registration of a sufficient number of partial 3-D range images in order to completely reproduce the model of the real object. If redundancy exists among the partial models composing the measured entity, a global adjustment of the model components improves the final accuracy with respect to a simple pairwise registration.
To this regard, a new solution for the optimal least squares registration of range images, based on the Generalised Procrustes Analysis techniques, has been recently developed by the authors and can be found in the literature. The method, using the classical tie point correspondence, has proven to be very efficient since it does not require any prior information of the geometrical relationship existing among the particular reference frames in which the different partial 3-D models are expressed. Considering its computational
advantages, it does not involve linearisation of equation systems nor matrix inversions, the only requirement is the singular value decomposition (SVD) of matrices of order 3 x 3.
In this paper a significant analytical enhancement of the Procrustean method is presented, to manage the stochastic properties of the tie point coordinates in a more complete and exhaustive way. In the previous formulation the possibility to assign a different isotropic weighting factor to the single tie points, according to their specific accuracy, was considered. With the new proposed method, also the positional components, i.e. each coordinate, can be weighted separately. In this way a complete anisotropic and inhomogeneous factored stochastic model can be introduced in the Procrustes procedure.
The generalisation of the stochastic model is recommended for certain practical applications, particularly for joining aerial laserscanners strips produced with low sampling density. In these cases, matching correspondence points of low resolution range images
generates poorly accurate tie point coordinate estimation. Indeed, this event introduces an uncertainty in the 3-D position that must be considered anisotropic, i.e. not affecting the three components of the same amount. In fact, considering one tie-point laying on a surface perpendicular to the laser beam, the effective position of the laser footprint on the correspondence element affects the planimetric position more than the related altimetric component. In these situations, the different quality of the tie points position
components must be correctly and advantageously preserved, performing the global registration adopting the anisotropic model here presented.
A suitable application is discussed in the paper to illustrate the registration problem and the expected advantages of the method proposed
La soluzione della triangolazione aerea a modelli indipendenti mediante tecniche di analisi procustiana
No full text- …
