1,720,984 research outputs found
Low-height aerial imagery and digital photogrammetrical processing for archaeological mapping
Full text linkIn the framework of the Joint Archaeological Mission of the Universities of Bologna and Lecce at the ancient town of Soknopaiou Nesos (Fayyum, Egypt) a wide-range of geomatic methodologies were experimented (GPS, total station surveys, low-height aerial and close-range photogrammetry, Visual Reality, high resolution satellite imagery, etc.). The surveys were conducted with the aim of recording metrical and non-metrical information inside a common reference system for the development of a GIS for the archaeological area.
The paper deals in particular with the acquisition and processing of low-height aerial imagery to provide very large-scale mapping of the area in support of archaeological researches. A remote controlled system, ad hoc developed for cultural heritage applications, permits to operate both semi-metric and non-metric cameras, lifted by balloon or kites with specific arrangements, in order to systematically take pictures over the study area.
The images acquired during the 2002 campaign by a non-metrical camera, calibrated by field calibration procedure, were processed within a Socet Set digital photogrammetric workstation: aero-triangulation, digital orthoimage generation and mosaicing were realized. The external orientation was established through kinematic GPS-derived ground control points, surveyed within the International Terrestrial Reference Frame ITRF2000; the same kinematic survey provided also a DTM for the entire site.
After a description of the overall approach to the survey of the site by the integration of different techniques, the paper describes the results obtained by this photogrammetric campaign, pointing out specifically the aspects concerning the non-standard image arrangement within the photogrammetric block, the problems arised by the geometrical structure of the buildings (e.g. the presence of very high mud-bricks walls in the temenos), and the use and comparison of DTMs derived from image-matching techniques or from GPS surveys
Technical Challenges for Multi-Temporal and Multi-Sensor Image Processing Surveyed by UAV for Mapping and Monitoring in Precision Agriculture
Full text linkPrecision Agriculture (PA) is an approach to maximizing crop productivity in a sustainable manner. PA requires up-to-date, accurate and georeferenced information on crops, which can be collected from different sensors from ground, aerial or satellite platforms. The use of optical and thermal sensors from Unmanned Aerial Vehicle (UAV) platform is an emerging solution for mapping and monitoring in PA, yet many technological challenges are still open. This technical note discusses the choice of UAV type and its scientific payload for surveying a sample area of 5 hectares, as well as the procedures for replicating the study on a larger scale. This case study is an ideal opportunity to test the best practices to combine the requirements of PA surveys with the limitations imposed by local UAV regulations. In the field area, to follow crop development at various stages, nine flights over a period of four months were planned and executed. The usage of ground control points for optimal georeferencing and accurate alignment of maps created by multi-temporal processing is analyzed. Output maps are produced in both visible and thermal bands, after appropriate strip alignment, mosaicking, sensor calibration, and processing with Structure from Motion techniques. The discussion of strategies, checklists, workflow, and processing is backed by data from more than 5000 optical and radiometric thermal images taken during five hours of flight time in nine flights throughout the crop season. The geomatics challenges of a georeferenced survey for PA using UAVs are the key focus of this technical note. Accurate maps derived from these multi-temporal and multi-sensor surveys feed Geographic Information Systems (GIS) and Decision Support Systems (DSS) to benefit PA in a multidisciplinary approach
Geodetic measurements to control a large research infrastructure. The Virgo detector at the European Gravitational Observatory
Full text linkThe Advanced Virgo (AdV) detector is a 3 km long arms Michelson interferometer for gravitational waves detection. The management of a complex and large research infrastructure requires high-precision geodetic surveying for positioning and rearrangement of instruments.
This paper describes the establishment of Virgo Reference System (VRS) consisting in a wide-scale high precision geodetic network based on GPS and Total Station measurements, that support the positioning and the alignment of the different elements forming the interferometer. Ground settlement monitoring is strictly required to verify and adapt the interferometer vertical alignment in presence of a steady subsidence process due to infrastructures overloads. The paper describes also the monitoring activity conducted over the years by means of periodic high precision levelling, that was compared with the results with those obtained using differential interferometry based on satellite Synthetic Aperture Radar (SAR) data
Historical photogrammetry & terrestrial laser scanning for the 3D virtual reconstruction of destroyed structures: A case study in Italy
No full textThe current dramatic episodes of destruction of archaeological sites have again highlighted the problem of the safeguarding the threatened heritage and, if possible, recovering those damaged by all the armed conflicts of the past. The historical photogrammetry offers the possibility to recover a posteriori the geometrical and material properties of destroyed structures, reconstructing their 3D model to document, study and maintain their memory, until to support their real anastylosis. The presented work is about the 3D reconstruction of the civic tower of the little town of Sant'Alberto, near the city of Ravenna, Italy. The tower, as a symbol of resistance and pride of the town's population, was destroyed in December 1944 by German troops in retaliation, when they were forced to leave the area. A city committee has subsequently collected all the historical evidence concerning the tower, including a series of photographic images that can be used for the photogrammetric reconstruction; the images calibration and orientation have been solved using the geometric information derived by a terrestrial laser scanner survey realized in the area where the tower was originally located. Despite the scarcity and very poor quality of the available images, the conducted photogrammetric procedure has allowed a complete and qualitatively satisfying object reconstruction, also thanks to the use of geometric constraint tools offered by the chosen software. The integration between the obtained model of the old tower and the 3D TLS survey of the square made it possible to reconstruct the ancient situation of the area
Integrazione di tecniche geomatiche per applicazioni di agricoltura di precisione nel progetto LIFE AGROWETLANDS II
No full text3D GEOMATICS TECHNIQUES FOR AN INTEGRATED APPROACH TO CULTURAL HERITAGE KNOWLEDGE: THE CASE OF SAN MICHELE IN ACERBOLI’S CHURCH IN SANTARCANGELO DI ROMAGNA
Full text linkThe modern Geomatics techniques, such as Terrestrial Laser Scanner (TLS) and multi-view Structure from Motion (SfM), are
gaining more and more interest in the Cultural Heritage field. All the data acquired with these technologies could be stored and
managed together with other information in a Historical Building Information Model (HBIM).
In this paper, it will be shown the case study of the San Michele in Acerboli’s church, located in Santarcangelo di Romagna, Italy.
This church, dated about the 6th century A.D., represents a high relevant Romanic building of the high Medieval period. The
building presents an irregular square plan with a different length of the lateral brick walls and a consequential oblique one in
correspondence of the apse. Nevertheless, the different lengths of the lateral brick walls are balanced thanks to the irregular spaces
between the windows. Different changes occurred during the centuries, such as the closing of the seven main doors and the building
of the bell tower, in the 11th century A.D., which is nowadays the main entrance of the church.
An integrated survey was realized, covering the exterior and the interior. The final 3D model represents a valid support not only for
documentation, but also to maintain and manage in an integrate approach the available knowledge of this Cultural Heritage site,
developing a HBIM system in which all the mentioned historical, geometrical, material matters are collected
Assessing Hazardous Spills Impact on Road Surface Performances by 3D High Resolution Surveying Techniques
No full textSurface texture of a road pavement is recognized as one of the most
relevant parameters in driving safety. Spillages on the highway can lead to dangerous
conditions for road users and cause damage to the road surface. Hazardous
substance spills caused by traffic accidents threaten the safety road and request a
specific clearance operation to reduce the risk of asphalt surface degradation. The
aim of this paper is to evaluate the effect of usual hazardous liquids spilled during
traffic accidents from vehicles on the asphalt properties and related safety parameters.
The experimental application is performed via digital photogrammetry. The
application of 3D geomatic techniques allows to calculate new texture indicators
through geometric and colorimetric information more accurate than traditional
survey techniques. The proposed approach can constitute a new useful investigation
method, in addition to traditional surveys, which are slower and less precise.
The texture reading by using three-dimensional analysis is an innovative way to
obtain and compare the traditional performance indicators used to measure friction
with new proposed indicators. In particular, the described experience evidences
the mechanical behaviour and the structural damage of asphalt samples related
to different exposure times treated with five hazardous liquids. Both traditional
and innovative techniques are carried out to evaluate roughness (British Pendulum
Number, BPN). The obtained results show how the various substances affect in
different way the samples asphalt surface
High-Detail 3D Reconstruction and Digital Strategies for the Enhancements of Archaeological Properties in Museums
Full text linkIn recent years, increasing attention has been directed toward the application of
digitization through geomatic-based technologies for museum assets. These powerful tools have proven valuable in assisting museums in the dissemination of cultural heritage. Additionally, museums around the world are implementing strategies to improve the accessibility of their assets by involving the use of 3D digital reconstruction. The 3D high-precision survey is employed in several fields to scan objects with a geometrical accuracy up to the micrometer level. These technologies come into play when dealing with detailed surfaces and complex geometry, as often occurs with cultural heritage assets. This paper presents a set of experiences in high-precision 3D scanning and post-processing operations in the framework of a project at the Territory Museum of Riccione (Italy). The 3D data acquisition methodology conducted and digital operations are reported on for some of the scanned artifacts
A Comparative Study of the Applied Methods for Estimating Deflection of the Vertical in Terrestrial Geodetic Measurements
Full text linkThis paper compares three different methods capable of estimating the deflection of the vertical (DoV): one is based on the joint use of high precision spirit leveling and Global Navigation Satellite Systems (GNSS), a second uses astro-geodetic measurements and the third gravimetric geoid models. The working data sets refer to the geodetic International Terrestrial Reference Frame (ITRF) co-location sites of Medicina (Northern, Italy) and Noto (Sicily), these latter being excellent test beds for our investigations. The measurements were planned and realized to estimate the DoV with a level of precision comparable to the angular accuracy achievable in high precision network measured by modern high-end total stations. The three methods are in excellent agreement, with an operational supremacy of the astro-geodetic method, being faster and more precise than the others. The method that combines leveling and GNSS has slightly larger standard deviations; although well within the 1 arcsec level, which was assumed as threshold. Finally, the geoid model based method, whose 2.5 arcsec standard deviations exceed this threshold, is also statistically consistent with the others and should be used to determine the DoV components where local ad hoc measurements are lacking
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