94 research outputs found
Coastal Altimetry Benefits From CryoSat-2 Synthetic Aperture Measurements (report on 6th Coastal Altimetry Workshop; Riva del Garda, Italy, 20–21 September 2012)
No full textThe scientific community involved in the research and development of applications of satellite altimetry in the coastal zone met for the 6th Coastal Altimetry Workshop. Research in coastal altimetry is going through exciting times: Experimental data sets for the coastal zone are now available, such as those from the French PISTACH project for the Jason-2 satellite and from the European Space Agency (ESA)–funded COASTALT project for the Envisat satellite, and many diverse applications were shown at the workshop. These range from observing coastal currents to monitoring river and lake levels, ice margins, and storm surges to gravity mapping in coastal zones
The Coastal Zone: A Mission Target for Satellite Altimeters
Get PDFSynthetic aperture radar (SAR) altimetry is rapidly becoming the most efficient way to measure small-scale changes in elevations of ice, land, and water surfaces as well as sea ice thickness. This new generation altimeter, first launched on board the CryoSat-2 satellite, fires 10 times more radar pulses per second than the previous generation and exploits the motion of the spacecraft to achieve a 20-fold increase in along-track resolution and twofold improvement in its accuracy
Modeling Envisat RA-2 waveforms in the coastal zone: case-study of calm water contamination
Get PDFRadar altimeters have so far had limited use in the coastal zone, the area with most societal impact. This is due to both lack of, or insufficient accuracy in the necessary corrections, and more complicated altimeter signals. This paper examines waveform data from the Envisat RA-2 as it passes regularly over Pianosa (a 10 km2 island in the NW Mediterranean). Forty-six repeat passes were analysed, with most showing a reduction in signal upon passing over the island, with weak early returns corresponding to the reflections from land. Intriguingly one third of cases showed an anomalously bright hyperbolic feature. This feature may be due to extremely calm waters in the Golfo della Botte (northern side of the island), but the cause of its intermittency is not clear. The modelling of waveforms in such a complex land/sea environment demonstrates the potential for sea surface height retrievals much closer to the coast than is achieved by routine processing. The long-term development of altimetric records in the coastal zone will not only improve the calibration of altimetric data with coastal tide gauges, but also greatly enhance the study of storm surges and other coastal phenomena
RTM Inversion through Predictive Equations for Multi-Crop LAI Retrieval Using Sentinel-2 Images
Get PDFNear-real-time, high-spatial-resolution leaf area index (LAI) maps would enable producers to monitor crop health and growth status, improving agricultural practices such as fertiliser and water management. LAI retrieval methods are numerous and can be divided into statistical and physically based methods. While statistical methods are generally subject to high site-specificity but possess high ease of implementation and use, physically based methods are more transferable, albeit more complex to use in operational settings. In addition, statistical methods need a large amount of data for calibration and subsequent validation, and this is only seldom feasible. Techniques based on predictive equations (PEphysical) represent a viable alternative, allowing the partial combination of statistical and physical methods merits while minimising their shortcomings. In this paper, predictive equation-based techniques were compared with four other methods: two radiative transfer model (RTM) inversion methods, one based on neural network (NNET) and one based on a look-up table (LUT), and two empirical methods (one using empirical models based on vegetation indices and in situ data and one based on empirical models found in the scientific literature). The methods were chosen based on common use. To evaluate the performance of the studied methods, the coefficient of determination (R2), root mean square error (RMSE), and normalised root mean square error (nRMSE, %) between the estimates and in situ LAI measurements were reported. The best PEphysical results, achieved by the OSAVI index (RMSE = 0.84 m2 m−2), provided better performance for LAI recovery than the NNET-based RTM inversions (0.86 m2 m−2) or the estimates made by LUT (0.94 m2 m−2). Furthermore, the best PEphysical produced accuracies comparable to the best empirical model (RMSE = 0.71 m2 m−2), calibrated through in situ data, and similar to the best literature model (RMSE = 0.76 m2 m−2). These results indicated that PEphysical can be used to recover LAI with transferability comparable to literature models
Satellite Altimetry and Seasonal Circulation in the Ligurian Sea
No full textSatellite altimetry observations are checked against in situ measurements to assess the capability of this remote sensing technique to describe the surface circulation in the Ligurian Sea. CTD profiles were collected during five oceanographic campaigns from 2017 and 2024 along the satellite track Jason 044, crossing the Ligurian Sea from the Corsica Channel to the coast close to Genoa. Eight months of ADCP surface currents from a fixed mooring were also used for the comparison with altimetric-derived geostrophic currents. Moreover, the possible contribution of ICESat-2 to oceanographic studies in the area is investigated. Altimetric measurements successfully reproduce the basic circulation features of the region and their seasonal variation and, despite the different nature of the used systems, can be well integrated with in situ observations. The results from the direct comparison with daily mean values of ADCP surface currents reported an RMSD of the same order as the standard deviation, which is consistent with similar investigations in other areas but evidences the need to define more appropriate metrics and methods
ALES: a multi-mission adaptive subwaveform retracker for coastal and open ocean altimetry
Get PDFSatellite altimetry has revolutionised our understanding of ocean dynamics thanks to frequent sampling and global coverage. Nevertheless, coastal data have been flagged as unreliable due to land and calm water interference in the altimeter and radiometer footprint and uncertainty in the modelling of high-frequency tidal and atmospheric forcing.
Our study addresses the first issue, i.e. altimeter footprint contamination, via retracking, presenting ALES, the Adaptive Leading Edge Subwaveform retracker. ALES is potentially applicable to all the pulse-limited altimetry missions and its aim is to retrack both open ocean and coastal data with the same accuracy using just one algorithm.
ALES selects part of each returned echo and models it with a classic “open ocean” Brown functional form, by means of least square estimation whose convergence is found through the Nelder–Mead nonlinear optimisation technique. By avoiding echoes from bright targets along the trailing edge, it is capable of retrieving more coastal waveforms than the standard processing. By adapting the width of the estimation window according to the significant wave height, it aims at maintaining the accuracy of the standard processing in both the open ocean and the coastal strip.
This innovative retracker is validated against tide gauges in the Adriatic Sea and in the Greater Agulhas System for three different missions: Envisat, Jason-1 and Jason-2. Considerations of noise and biases provide a further verification of the strategy. The results show that ALES is able to provide more reliable 20-Hz data for all three missions in areas where even 1-Hz averages are flagged as unreliable in standard products. Application of the ALES retracker led to roughly a half of the analysed tracks showing a marked improvement in correlation with the tide gauge records, with the rms difference being reduced by a factor of 1.5 for Jason-1 and Jason-2 and over 4 for Envisat in the Adriatic Sea (at the closest point to the tide gauge)
POSITIVE: A SMART IRRIGATION PROJECT FOR AGRICULTURE 4.0 | POSITIVE: UN PROGETTO DI IRRIGAZIONE INTELLIGENTE PER L'AGRICOLTURA 4.0
No full textPOSITIVE (Scalable Operational Protocols for precision agriculture) is a precision agriculture project for variable rate irrigation designed to improve the functionality of the IRRIFRAME system, the irrigation advice service of the Emilia-Romagna region. POSITIVE is based on satellite remote sensing, the use of vegetation indices for crops, IoT (Internet of Things) technologies, Big Data and 4.0 irrigation machinery. A central server manages the information flows and provides variable rate irrigation maps for farmers as final users. The system is public and free. In the first year of "IRRIFRAME plus" system experimentation (improved version of IRRIFRAME through POSITIVE machinery), at the experimental farm located in Mezzolara di Budrio (BO - Italy), promising results have been obtained for maize, with a WUE (Water Use Efficiency) going from 4.2 g l-1 (with standard IRRIFRAME service) to 5.2 g l-1. For sparse crops, such as tomato and
onion, results were not so satisfactory. The future years of experimentation will allow to improve the calibration of VI-crop coefficient (Kc) correlation in order to improve the response in condition of partial soil cover and wetting condition
Detection and Characterization of Ship Targets Using CryoSat-2 Altimeter Waveforms
No full textThis article describes an investigation of the new possibilities offered by SAR altimetry compared with conventional altimetry in the detection and characterization of non-ocean targets. We explore the capabilities of the first SAR altimeter installed on the European Space Agency satellite CryoSat-2 for the detection and characterization of ships. We propose a methodology for the detection of anomalous targets in the radar signals, based on the advantages of SAR/Doppler processing over conventional altimetry. A simple metric is proposed for the automatic detection and separation of ship targets; additional geometric considerations are introduced, to assess the compatibility between the structures detected and the actual location and characteristics of the ships observed. A test-case is presented with multiple targets that are confirmed as large vessels cruising in the proximity of a CryoSat-2 track crossing the Alboran Sea (Western Mediterranean). The presence and position of these ships at the time of satellite passage have been corroborated by the data retrieved from the Automatic Information System database. A principal motive for this research is the future altimetry missions that will provide global SAR coverage (e.g., Sentinel-3). This methodology may complement the existing tracking systems, with particular reference to the capability of compiling global statistics based on freely available data
Layered nature. Assessing and monitoring the environment for the development of an archaeological park
No full textThe case study of Tilmen Höyük is presented here to describe a combination of different integrated approaches. The site has been assessed from a climatic, topographical, pedological, hydrological, vegetational and vegetation management standpoint. This study provided a wealth of information that was used for acquiring a deeper understanding of the present environment, in view also of designing and planning the archaeological park. At the same time, remote monitoring was experimented in view of future applications and management protocols
Augmented Reality in Dental Extractions: Narrative Review and an AR-Guided Impacted Mandibular Third-Molar Case
Get PDFBackground: Augmented-reality (AR) navigation is emerging as a means of turning pre-operative cone-beam CT data into intuitive, in situ guidance for difficult tooth removal, yet the scattered evidence has never been consolidated nor illustrated with a full clinical workflow. Aims: This study aims to narratively synthesise AR applications limited to dental extractions and to illustrate a full AR-guided clinical workflow. Methods: We performed a PRISMA-informed narrative search (PubMed + Cochrane, January 2015–June 2025) focused exclusively on AR applications in dental extractions and found nine eligible studies. Results: These pilot reports—covering impacted third molars, supernumerary incisors, canines, and cyst-associated teeth—all used marker-less registration on natural dental surfaces and achieved mean target-registration errors below 1 mm with headset set-up times under three minutes; the only translational series (six molars) recorded a mean surgical duration of 21 ± 6 min and a System Usability Scale score of 79. To translate these findings into practice, we describe a case of AR-guided mandibular third-molar extraction. A QR-referenced 3D-printed splint, intra-oral scan, and CBCT were fused to create a colour-coded hologram rendered on a Magic Leap 2 headset. The procedure took 19 min and required only a conservative osteotomy and accurate odontotomy that ended without neurosensory disturbance (VAS pain 2/10 at one week). Conclusions: Collectively, the literature synthesis and clinical demonstration suggest that current AR platforms deliver sub-millimetre accuracy, minimal workflow overhead, and high user acceptance in high-risk extractions while highlighting the need for larger, controlled trials to prove tangible patient benefit
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