1,721,072 research outputs found
Editorial for special issue: “Geomatics application for geography (gag)” in geographia technica
Full text linkGeomatics or Geography, that is the question!
This is how the authors' idea of merging Geomatics and Geography in this special issue begins, paraphrasing a Shakespearean citation. The common principle that unites these two scientific disciplines, which attempt to describe the territory in the most straightforward way possible. On the other hand, Geomatics and Geography derived from “gèo- “[greek γεω-], as first element of composed words in learned and scientific terminology, meaning “earth”, “globe”, “land surface”
Unmanned aerial vehicle for post seismic and other hazard scenarios
No full textOn April 6, 2009, an earthquake hits the old city of L’Aquila resulting in hundreds of victims and thousands of collapses. The post emergency and very crucial phase regarding surveys, structure controls and investigations till now is fully underway. Conventional surveying techniques using high precision total stations, GNSS and laser scanners, are instruments of extreme operability but here are still many evident limits on their use especially regarding the survey of both the roofs and the facades of tall buildings or dangerous places, typical in post earthquake situations. Another very important disadvantage of the traditional surveying, especially during the post seismic periods, regards the overall safety of the instruments, operators and workers. In particular, the seismic sequence that may last for months after the main shock, causing collapses and ulterior damage that in most cases can also damage the transport and communication infrastructure creating important problems for all instruments located in that area and definitely posing a further serious risk for all operators. Moreover, some surveys have to be repeated periodically in order to achieve a final result. On the other hand, by using micro UAVs (Unmanned Aerial Vehicles) for surveying in such particular scenarios, many of these problems can easily bypassed. For example, there are no accessibility problems for an UAV mainly because of its extreme flying capabilities that can really permit the access of virtually any place. Regarding the security, these instruments are fully remotely controlled, so they do not involve any risk for the operators simply because they are in the dangerous area. For these reasons, in this work, we’ll explain the advantages of multirotor UAVs, fully remotely controlled, to acquire roofs and facades of structures in an old city center damaged by a seismic sequence like L’Aquila city
Assessment of dual frequency GNSS observations from a Xiaomi Mi 8 android smartphone and positioning performance analysis
Full text linkOn May 2018 the world’s first dual-frequency Global Navigation Satellite System (GNSS) smartphone produced by Xiaomi equipped with a Broadcom BCM47755 chip was launched. It is able to receive L1/E1/ and L5/E5 signals from GPS, Galileo, Beidou, and GLONASS (GLObal NAvigation Satellite System) satellites. The main aim of this work is to achieve the phone’s position by using multi-constellation, dual frequency pseudorange and carrier phase raw data collected from the smartphone. Furthermore, the availability of dual frequency raw data allows to assess the multipath performance of the device. The smartphone’s performance is compared with that of a geodetic receiver. The experiments were conducted in two different scenarios to test the smartphone under different multipath conditions. Smartphone measurements showed a lower C/N0 and higher multipath compared with those of the geodetic receiver. This produced negative effects on single-point positioning as showed by high root mean square error (RMS). The best positioning accuracy for single point was obtained with the E5 measurements with a DRMS (horizontal root mean square error) of 4.57 m. For E1/L1 frequency, the 2DRMS was 5.36 m. However, the Xiaomi Mi 8, thanks to the absence of the duty cycle, provided carrier phase measurements used for a static single frequency relative positioning with an achieved 2DRMS of 1.02 and 1.95 m in low and high multipath sites, respectively
Comparison of the materialisation of the tide gauges in use in Italy as support for the correct implementation of the national seagrass mapping project
No full textThe definition of a reference system is the first moment of a survey operation but is in some ways perhaps the most critical because on its correct definition depends on the reliability and significance of all subsequent operations. From the simplest local survey to the most complex surveys of large extensions that often require the joint use of different technologies, it is in fact of paramount importance to define a planimetric or planoaltimetric datum that allows all subsequent survey operations to be correctly referenced and make the various observations consistent. In this paper we illustrate the first considerations that have been made for the correct framing of the high-resolution bathymetric surveys of a future national project to survey all the coastal areas and the relative seafloor for the entire Italian coastline; peninsula, major islands and minor islands. The different geomatic techniques that will necessarily be used require the study and definition of certain methodologies to refer all observations to a common reference to ensure compatibility and comparability. Particularly critical is the altimetry aspect for which it is necessary to consider the shift between ellipsoid heights, orthometric heights and heights referring to the local mean sea level. It is precisely the last transition that is perhaps the most critical because it requires the local study of the framing and materialisation of the tide gauges. The main tide gauges of the national system have been studied here, confirming the complexity of this certain definition and suggesting possible developments in the definition of conversion methodologies
Intensive archaeological survey at Piscina Torta: use of a low-cost RTK portable kit to materialise a UTM grid on the ground
Full text linkWe tested the use of a low-cost GPS RTK to set up a grid during the intensive archaeological survey of the Piscina Torta site, in the framework of the Salt and Power project of the University of Groningen. We also suggest not using a local grid but the WGS84 UTM grid and naming the single cells with the coordinates of one of its vertices. This would facilitate the use and exchange of the data (e.g. about the potsherds collected in the cell) among the scientific community
Utilizzo delle immagini satellitari ad alta risoluzione come supporto al monitoraggio della zona costiera
No full textFirst considerations on post processing kinematic GNSS data during a geophysical oceanographic cruise
Full text linkDifferential GNSS positioning on vessels is of considerable interest in various fields of application as navigation aids, precision positioning for geophysical surveys or sampling purposes especially when high resolution bathymetric surveys are conducted. However ship positioning must be considered a kinematic survey with all the associated problems. The possibility of using high-precision differential GNSS receivers in navigation is of increasing interest, also due to the very recent availability of low-cost differential receivers that may soon replace classic navigation ones based on the less accurate point positioning technique. The availability of greater plano-altimetric accuracy, however, requires an increasingly better understanding of planimetric and altimetric reference systems. In particular, the results allow preliminary considerations on the congruence between terrestrial reference systems (which the GNSS survey can easily refer to) and marine reference systems (connected to National Tidegauge Network). In spite of the fluctuations due to the physiological continuous variation of the ship's attitude, GNSS plot faithfully followed the trend of the tidal variations and highlighted the shifts between GNSS plot and the tide gauges due to the different materialization of the relative reference systems
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