177,326 research outputs found
ACCURACY ASSESSMENT OF 3D MODELS GENERATED FROM GOOGLE STREET VIEW IMAGERY
No full textGoogle Street View is a technology implemented in several Google services/applications (e.g. Google Maps, Google Earth) which provides the user, interested in viewing a particular location on the map, with panoramic images (represented in equi-rectangular projection) at street level. Generally, consecutive panoramas are acquired with an average distance of 5–10 m and can be compared to a traditional photogrammetric strip and, thus, processed to reconstruct portion of city at nearly zero cost. Most of the photogrammetric software packages available today implement spherical camera models and can directly process images in equi-rectangular projection. Although many authors provided in the past relevant works that involved the use of Google Street View imagery, mainly for 3D city model reconstruction, very few references can be found about the actual accuracy that can be obtained with such data. The goal of the present work is to present preliminary tests (at time of writing just three case studies has been analysed) about the accuracy and reliability of the 3D models obtained from Google Street View panoramas
A RESTORATION ORIENTED HBIM SYSTEM FOR CULTURAL HERITAGE DOCUMENTATION: THE CASE STUDY OF PARMA CATHEDRAL
No full textThe need to safeguard and preserve Cultural Heritage (CH) is increasing and especially in Italy, where the amount of historical buildings is considerable, having efficient and standardized processes of CH management and conservation becomes strategic. At the time being, there are no tools capable of fulfilling all the specific functions required by Cultural Heritage documentation and, due to the complexity of historical assets, there are no solution as flexible and customizable as CH specific needs require. Nevertheless, BIM methodology can represent the most effective solution, on condition that proper methodologies, tools and functions are made available. The paper describes an ongoing research on the implementation of a Historical BIM system for the Parma cathedral, aimed at the maintenance, conservation and restoration.
Its main goal was to give a concrete answer to the lack of specific tools required by Cultural Heritage documentation: organized and coordinated storage and management of historical data, easy analysis and query, time management, 3D modelling of irregular shapes, flexibility, user-friendliness, etc.
The paper will describe the project and the implemented methodology, focusing mainly on survey and modelling phases. In describing the methodology, critical issues about the creation of a HBIM will be highlighted, trying to outline a workflow applicable also in other similar contexts
Where is photogrammetry heading to? State of the art and trends
No full textThe objective of this paper is to highlight current trends in photogrammetry, trying to foresee where they will lead the discipline in the next years. To this aim, first some remarks on the challenges brought to photogrammetry by other sensors and a brief historical survey of some research topics, where an increasing convergence between photogrammetry and computer vision is apparent, will be presented. Then, a necessarily concise review of the advances in automation in three basic photogrammetric tasks (namely image orientation, surface reconstruction and object restitution) will be illustrated. The purpose of the review is to highlight how the fruitful dialog between photogrammetry and computer vision led to today’s achievements and to point out what kind of approaches seem to be winning in the search for viable and robust solutions in the automation of processes. Finally, the conclusions will look at this convergence in the perspective of academic career
UAV Block Geometry Design and Camera Calibration: A Simulation Study
No full textAcknowledged guidelines and standards such as those formerly governing project planning in analogue aerial photogrammetry are still missing in UAV photogrammetry. The reasons are many, from a great variety of projects goals to the number of parameters involved: camera features, flight plan design, block control and georeferencing options, Structure from Motion settings, etc. Above all, perhaps, stands camera calibration with the alternative between pre- and on-the-job approaches. In this paper we present a Monte Carlo simulation study where the accuracy estimation of camera parameters and tie points’ ground coordinates is evaluated as a function of various project parameters. A set of UAV (Unmanned Aerial Vehicle) synthetic photogrammetric blocks, built by varying terrain shape, surveyed area shape, block control (ground and aerial), strip type (longitudinal, cross and oblique), image observation and control data precision has been synthetically generated, overall considering 144 combinations in on-the-job self-calibration. Bias in ground coordinates (dome effect) due to inaccurate pre-calibration has also been investigated. Under the test scenario, the accuracy gap between different block configurations can be close to an order of magnitude. Oblique imaging is confirmed as key requisite in flat terrain, while ground control density is not. Aerial control by accurate camera station positions is overall more accurate and efficient than GCP in flat terrain
HBIM for conservation: A new proposal for information modeling
No full textThanks to its capability of archiving and organizing all the information about a building, HBIM (Historical Building Information Modeling) is considered a promising resource for planned conservation of historical assets. However, its usage remains limited and scarcely adopted by the subjects in charge of conservation, mainly because of its rather complex 3D modeling requirements and a lack of shared regulatory references and guidelines as far as semantic data are concerned. In this study, we developed an HBIM methodology to support documentation, management, and planned conservation of historic buildings, with particular focus on non-geometric information: organized and coordinated storage and management of historical data, easy analysis and query, time management, flexibility, user-friendliness, and information sharing. The system is based on a standalone specific-designed database linked to the 3D model of the asset, built with BIM software, and it is highly adaptable to different assets. The database is accessible both with a developed desktop application, which acts as a plug-in for the BIM software, and through a web interface, implemented to ensure data sharing and easy usability by skilled and unskilled users. The paper describes in detail the implemented system, passing by semantic breaking down of the building, database design, as well as system architecture and capabilities. Two case studies, the Cathedral of Parma and Ducal Palace of Mantua (Italy), are then presented to show the results of the system's application
Air-Fuel Ratio Adaptive Control for Two-Stroke S.I. Engines with Direct Injection
No full textIn two-stroke S.I. engines, direct fuel injection prevents fuel short-circuiting from the exhaust port. Charge
stratification helps solving combustion problems at light loads due to excessive ratio of residual-to-fresh gas,
however it requires precise determination of the air-fuel ratio. Unfortunately, this ratio undergoes unpredictable
variations during engine life, on account of variations of trapping efficiency, mainly caused by carbon deposits.
A customary closed-loop control strategy cannot be adopted, since exhaust gas contains short-circuit air. The
purpose of the paper is to show that the problem can be solved with the adoption of an innovative diagnostic
and control method.
A special test strategy, which is activated both periodically and/or when suitable data are not congruent, allows
to acquire and refresh information on short-circuit oxygen. This makes it possible to operate an adaptive
control of air-fuel ratio, based on the use of a proportional oxygen sensor
Tra conservazione e innovazione: un HBIM per il Duomo di Parma
No full textThe BIM methodology is now more and more widespread. While it is consolidating in the field of new buildings, in the field of Cultural Heritage, many questions are still open. The paper describes an ongoing research on the creation of a HBIM for the Cathedral of Parma, aimed at the planned conservation. HBIM was designed as an information system on the architectural scale. It allows interaction between the 3D model of the building and a specifically structured external database in order to manage all data about the building in a consistent and coordinated way
The influence of laying patterns on the behaviour of historic stone pavements subjected to horizontal loads
No full textStone pavements are of great importance both for their historical and cultural value and for the most modern ecological and aesthetic requirements appreciated thanks to the use of natural materials of different colours, shapes and sizes which are laid in different patterns. Since stone block pavements are made up of individual elements with irregular side surfaces that interact with each other, an important parameter that must be considered in the design is their structural strength to horizontal stresses mainly due to braking, turning and accelerating vehicles. In this study horizontal load tests were performed on stone pavements built in a wide laboratory test chamber to analyse the load-shifting behaviour for different geometric arrangements. The displacements distribution of the elements was determined by a photogrammetric analysis. The tests have shown that the behaviour of the stone pavements in the horizontal plane is significantly influenced by the laying pattern, both in terms of translations and interaction between the elements. © 2020 Elsevier Lt
- …
