1,720,999 research outputs found
Levelling and GPS networks to monitor ground subsidence in the Southern Po Valley
No full textAfter a short historical introduction to the problem of the subsidence in the Po Valley, some results are shown of levelling campaigns carried out by various authorities or agencies in recent years, mainly in the southeast part of the Po Valley. We also present the results obtained along the coastline using the GPS technique both in a static and in fast-static modes. Attention is focused on the problem of the homogeneity of data from different sources, different periods and using different reference benchmarks. To overcome these problems, we propose a general levelling network covering the whole area of the valley, south of the Po river, connected with a GPS network of more than 50 points. This network will represent a spatial and temporal reference framework for all the measurements made in the past and for those planned for the future. A data information system has been implemented in order to organise and manage all available data in a well defined and homogeneous framework. This system will make it possible to store other related data, such as the pattern of the water table. geological evidences, land use, etc. (C) 2000 Elsevier Science Ltd. All rights reserved
GPS statico e statico rapido: effetto della configurazione satellitare
No full textVengono analizzati gli effetti della geometria satellitare sull'accuratezza di baselines GPS determinate in modalità statica o statico-rapida in post-processamento, in relazione ai valori assunti da indici di qualità della configurazione geometrica specifici per il posizionamento relativ
Confronto tra diverse modalità di elaborazione nel calcolo di reti GPS
No full textViene valutato l'effetto della strategia di calcolo nel caso di una rete GPS di baselines determinate in modalità statica, confrontando diversi approcci possibili (singola base, multibase, multisessione) ed esemplificando con dati real
Digital Orthophoto as a tool for the restoration of monuments.
Full text linkFor the restoration of monuments it is now becoming normal practice to carry out a preliminary study of the monument
before starting any kind of work. The metric survey is one of the main operations required. For this reason,
photogrammetry applications already have a large bibliography. In particular, digital photogrammetry is currently an
effective system, providing different solutions of both the vector and raster type.
For an 18th-century gate in the Malta fortification walls, many tests were carried out in order to establish a suitable
procedure for the creation of digital orthophotos. A photographic metric product, showing maximum detail without
subjective interpretation of the object and the conditions of the material, could be very interesting in supporting any
restoration work. The use of automatic procedures is also particularly suitable where large-scale surveys have to be
carried out on very large objects with homogeneous characteristics, as is the case with the Malta fortification Walls. The
advantages of digital over manual processing lie in the possibility of measuring a very large number of points without
fatigue and with a high level of productivity. Digital orthophotos require a digital surface model as input, but the
production of a high-fidelity reconstruction of surfaces by automatic measurement of points in close range
photogrammetry still remains an open problem. Particular difficulties are caused for instance by object details that are
not imaged or with strong shadows, or by complete failure of the image matching algorithms. Discontinuities in the
surface, very common in architectonic objects, complicate the generation of models and surfaces.
Within this work, several tests using commercial software were carried out, to define the best parameters for the
automatic generation of DSM (Digital Surface Model) related to the monument being studied. The initial tests are based
on the different dimension of the search window and the consequences of this choice on the accuracy and reliability of
the matching procedure. Further tests are related to the number of points needed to start the matching procedure: firstly,
points have been entered following a regular grid, then a greater number of points from the analytical plotting have been
entered. The results are compared, also taking in account practical and economic considerations.
Finally, different aspects for the creation of representative surfaces of the object have been analysed due to the non
planarity of the object, presence of linear discontinuities and noticeable overhangs.
The above-mentioned tests lead to several general considerations regarding strategies for creating orthophotos as a
suitable qualitative and quantitative tool for the restoration of a monument
Traditional and modern methods of surveying architectural heritage: a few examples in the fortified island of Malta.
No full textThe problem of the renewal and rehabilitation of the impressive fortifications system of the Republic of Malta has led
the Maltese government to operate in the framework of a far-reaching international cultural and financial
intervention. To this purpose a cooperation agreement was introduced between the Ministry for the Environment of
Malta and the University of Bologna. To attain this objective a multidisciplinary approach is necessary. Different
working groups must carry out specific actions concerning the acquisition of knowledge and execution of survey on
one hand and the design and execution of the interventions on the other.
In particular, the surveying activity is carried out at different levels:
• execution of an aerial photogrammetric survey on a scale of 1:500 for a deeper knowledge of the entire
intervention site;
• experimentation of an operational terrestrial photogrammetric survey methodology for different types of objects;
• topographical structural monitoring.
The experimentation on a few examples which will be described on this paper has led to the collection of a
considerable amount of metric information, thanks to the use of different topographic and photogrammetric
techniques and instruments. An element of great interest is linked to the possibility that a precision numeric
photogrammetric survey adequately oriented towards documentation concerning the restoration can support the
decision-taking procedures and the operational phases of the restoration thus allowing interesting developments with
a direct link with the cataloguing aspects
Digital orthophoto as a tool for the restoration of monuments
No full textFor the restoration of monuments it is now becoming normal practice to carry out a preliminary study of the monument before starting any kind of work. The metric survey is one of the main operations required. For this reason, photogrammetry applications already have a large bibliography. In particular, digital photogrammetry is currently an effective system, providing different solutions of both the vector and raster type. For an 18th-century gate in the Malta fortification walls, many tests were carried out in order to establish a suitable procedure for the creation of digital orthophotos. A photographic metric product, showing maximum detail without subjective interpretation of the object and the conditions of the material, could be very interesting in supporting any restoration work. The use of automatic procedures is also particularly suitable where large-scale surveys have to be carried out on very large objects with homogeneous characteristics, as is the case with the Malta fortification Walls. The advantages of digital over manual processing lie in the possibility of measuring a very large number of points without fatigue and with a high level of productivity. Digital orthophotos require a digital surface model as input, but the production of a high-fidelity reconstruction of surfaces by automatic measurement of points in close range photogrammetry still remains an open problem. Particular difficulties are caused for instance by object details that are not imaged or with strong shadows, or by complete failure of the image matching algorithms. Discontinuities in the surface, very common in architectonic objects, complicate the generation of models and surfaces. Within this work, several tests using commercial software were carried out, to define the best parameters for the automatic generation of DSM (Digital Surface Model) related to the monument being studied. The initial tests are based on the different dimension of the search window and the consequences of this choice on the accuracy and reliability of the matching procedure. Further tests are related to the number of points needed to start the matching procedure: firstly, points have been entered following a regular grid, then a greater number of points from the analytical plotting have been entered. The results are compared, also taking in account practical and economic considerations. Finally, different aspects for the creation of representative surfaces of the object have been analysed due to the non planarity of the object, presence of linear discontinuities and noticeable overhangs. The above-mentioned tests lead to several general considerations regarding strategies for creating orthophotos as a suitable qualitative and quantitative tool for the restoration of a monument
Methodological aspects for the survey of the architectural heritage: a few examples in the fortified island of Malta.
No full textAspetti metodologici per il rilievo del patrimonio architettonico: alcuni esempi nell’isola fortificata di Malta.
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