Preliminary Assessment Of Accuracy Research Articles

A REVIEW AND TEST OF SHORELINE EXTRACTION TECHNIQUES

Abstract. Shoreline represents the boundary between land and sea, and its accurate extraction is of utmost importance because of the economic and ecological value of coastal areas. Nowadays, satellite remote sensing is widely used for monitoring the natural environment. Indeed, satellite remote sensing data are cost-effective and periodically available over large areas at a relatively high spatial resolution. Hence, the automatic shoreline extraction from satellite images is a fundamental task for coastal monitoring and management. Shoreline extraction methods are usually applied to satellite remote sensing data. The goal of this study is to compare the performance of different shoreline extraction methods, such as thresholding and more complex classification approaches, such as Random Forest (RF), Minimum Distance (MD), Maximum Likelihood (ML) and K-means, using both optical and radar images. The considered case study area is the shallow basin of the Orbetello Lagoon and one of its ayre called Feniglia. The data supplier is the Copernicus program, which, through the Sentinel-1 and Sentinel-2 missions, provides medium-resolution, open-access products. The accuracy of the obtained results from both methodologies is checked by validating the extracted shoreline using an aerial orthomosaic and, subsequently, a manually extracted shoreline. A preliminary accuracy assessment was performed for image classification, focusing on extracting four classes: water, soil, urban, and forest, using manual segmentation as a reference. In terms of deviation from the reference shoreline, the results obtained through the analysed methodologies achieved an accuracy of 3.75 m, less than half of the pixel size of the Sentinel-1 and Sentinel-2 used products.

First Assessment of GF3-02 SAR Ocean Wind Retrieval

On 23 November 2021, the Gaofen-3-02 (GF3-02) satellite was successfully launched in the Jiuquan Satellite Launch Center of China. The primary payload is C-band Synthetic Aperture Radar (SAR), with a maximum resolution of 1 m, and includes 12 imaging modes such as Spotlight, Strip, and TOPSAR, which will play an essential role in marine environment monitoring. As an important marine environmental parameter, the wind speed accuracy retrieved by GF3-02 SAR directly reflects its performance and effectiveness as an operational product. Therefore, based on the wind data of buoys of the National Data Buoy Center (NDBC), ECMWF reanalysis V5 (ERA5), and HY-2B Scatterometer (SCA), a preliminary accuracy assessment of the wind speed retrieved by GF3-02 SAR is carried out in this paper. The wind speed retrieval accuracy of GF3-02 SAR in the co-polarization (HH+VV) data under different Geophysical Model Functions (GMFs) is discussed by using 478 level-1A Single Look Complex (SLC) ocean products acquired in Quad-Polarization Strip I (QPSI) and produced by the National Satellite Ocean Application Service (NSOAS) from January to March 2022. The results show that the optimal root mean square errors (RMSE) are 1.40 m/s, 1.18 m/s, and 1.24 m/s for the VV polarization and 1.39 m/s, 1.19 m/s, and 1.52 m/s for the HH polarization compared to the NDBC wind speed, the ERA5 wind speed, and the HY-2B SCA wind speed, respectively. The preliminary results show that GF3-02 SAR has good wind speed retrieval ability and can meet the needs of operational products.

Preliminary Accuracy Assessment of the F-Layer Worst-Case BDS Scintillation Observed by the GNOS Onboard the FY3D Satellite

Preliminary Accuracy Assessment of the F-Layer Worst-Case BDS Scintillation Observed by the GNOS Onboard the FY3D Satellite

Modeling In-Flight Ice Accretion Under Uncertain Conditions

In-flight ice accretion under parametric uncertainty is investigated. Three test cases are presented that reproduce experiments carried out at the NASA’s Glenn Icing Research Tunnel facility. A preliminary accuracy assessment, achieved by comparing numerical predictions against experimental observations, confirms the robustness and the predictiveness of the computerized icing model. Besides, sensitivity analyses highlight the variance of the targeted outputs with respect to the different uncertain inputs. In rime icing conditions, a predominant role is played by the uncertainty affecting the airfoil angle of attack, the cloud liquid water content, and the mean volume diameter of droplets. In glaze icing conditions, the sensitivity analysis shows instead that the output variability is due mainly to the ambient temperature uncertainty. Moreover, this paper exposes a challenge inherent in the approximation of the full icing model by means of standard (linear) polynomial chaos regression techniques. The complexity is related to the approximation of the model behavior in domain regions scarcely affected by ice buildup. To mitigate this issue, a nonlinear regression method is proposed and applied.

Design, Dynamic Analysis, and Experimental Evaluation of a Hybrid Parallel–Serial Polishing Machine With Decoupled Motions

Abstract In this paper, a novel six degrees-of-freedom (DOF) hybrid kinematic machine (HKM) is designed, analyzed, and evaluated for precision polishing. The design adopts a 3-DOF tripod-based parallel mechanism (PM) to locate the workpiece, a 2-DOF serial mechanism (SM) to orient the polishing tool, and a functional extension limb to provide a redundant DOF when polishing the workpieces with axially symmetrical shapes. Compared with the existing HKMs, the most distinctive feature is that the position and orientation adjustments of the tool with respect to the workpiece are decoupled during the synchronous machining, thus allowing the rotational tool center point (RTCP) function to be conveniently realized. For the developed HKM, the kinematics are studied systematically, including position, velocity, acceleration, and workspace. The dynamic model of the PM is derived by employing the principle of virtual work. For a pre-defined trajectory, the required driving forces are obtained through dynamic simulation. Based on these analyses, a laboratory prototype of the HKM is designed and developed. A preliminary accuracy assessment of the HKM is implemented with a double ball-bar, and a series of polishing experiments are conducted to show the capacity and feasibility of the developed HKM.

Sea ice modeling in the Sea of Azov for a study of long-term variability

This study deals with an attempt to use the NEMO modeling framework to investigate the long-term variability of the sea-ice fields in the Sea of Azov. A coupled ocean-ice model is used to perform a simulation by using an earlier developed configuration of cascading sea basins (Azov, Black, and Marmara). Various features of geographical location cause the formation of sea ice in the waters of the Sea of Azov and in the coastal area of the north-western Black Sea shelf. For a preliminary accuracy assessment, the simulation results are compared with the data based on satellite observations. The restricted amount of the data for the rather small area under study, as well as the features of the regional weather conditions, produce rather low accuracy of the available data products based on the satellite data. At the same time, the available data from coastal weather stations, as well as archived observations, produce a fairly adequate pattern of the simulated variability of the sea-ice conditions in the basin.

Surface albedo and toc-r 300 m products from PROBA-V instrument in the framework of Copernicus Global Land Service

PROBA-V instrument launched in 2013 is offering a global daily coverage at pixel resolutions of 333 m and 1 km in three spectral bands (BLUE, RED, NIR) and 600 m for shortwave infrared (SWIR). The PROBA-V mission is the follow-on of the VEGETATION program started in 2000, which allowed generating long-term series at 1 km pixel resolution. The PROBA-V products belong to the Copernicus Global Land Service portfolio (http://land.copernicus.eu/global/). The sensor design of PROBA-V with oriented cameras offers a wide field of view (FOV) for sampling the BRDF (Bidirectional Reflectance Distribution Function). This paper details the methodology implemented at the premises of VITO (Flemish Institute for Technological Research) with the aim to disseminate routinely from PROBA-V daily observations for both surface albedo (SA) and top-of-canopy corrected reflectance (TOC-R) products. The method classically operates a selection of cloudless scenes, performs atmospheric corrections, and finally applies a correction of directional effects on a pixel per pixel basis. The synthesis period is the decade and the composite period is 20 days. Such choice is a pointwise sampling as being a trade-off between the availability of clear scenes and the timescale for phenology. Regarding the albedo catalogue, a narrow-band to broadband conversion is stipulated. A recurrent technique serves for gap-filling based on the spread of weighed a priori data. Additional information concerns the quality flag and the age of the product. Preliminary accuracy assessment is performed through a comparison with the Moderate Imaging Spectroradiometer (MODIS) Collection 6. Dependable spatial consistency is reached except for wintertime with deviations in terms of rmse (root mean square errors) about 0.03 for visible and shortwave domains, and 0.04 for near infrared. Besides, both PROBA-V and MODIS C6 exhibit close time profiles, marked by smoothness or rapid transitions. Results over 10 confidence sites reveals rmse values of 0.032 and bias of 0.01 over the 2014 full annual cycle.

GF-3 SAR Ocean Wind Retrieval: The First View and Preliminary Assessment

Gaofen-3 (GF-3) is the first Chinese civil C-band synthetic aperture radar (SAR) launched on 10 August 2016 by the China Academy of Space Technology (CAST), which operates in 12 imaging modes with a fine spatial resolution up to 1 m. As one of the primary users, the State Oceanic Administration (SOA) operationally processes GF-3 SAR Level-1 products into ocean surface wind vector and plans to officially release the near real-time SAR wind products in the near future. In this paper, the methodology of wind retrieval at C-band SAR is introduced and the first results of GF-3 SAR-derived winds are presented. In particular, the case of the coastal katabatic wind off the west coast of the U.S. captured by GF-3 is discussed. The preliminary accuracy assessment of wind speed and direction retrievals from GF-3 SAR is carried out against in situ measurements from National Data Buoy Center (NDBC) buoy measurements of National Oceanic and Atmospheric Administration (NOAA). Only the buoys located inside the GF-3 SAR wind cell (1 km) were considered as co-located in space, while the time interval between observations of SAR and buoy was limited to less the 30 min. These criteria yielded 56 co-locations during the period from January to April 2017, showing the Root Mean Square Error (RMSE) of 2.46 m/s and 22.22° for wind speed and direction, respectively. Different performances due to geophysical model function (GMF) and Polarization Ratio (PR) are discussed. The preliminary results indicate that GF-3 wind retrievals are encouraging for operational implementation.

Low-Cost GNSS Receivers for Local Monitoring: Experimental Simulation, and Analysis of Displacements.

The geodetic monitoring of local displacements and deformations is often needed for civil engineering structures and natural phenomena like, for example, landslides. A local permanent GNSS (Global Navigation Satellite Systems) network can be installed: receiver positions in the interest area are estimated and monitored with respect to reference stations. Usually, GNSS geodetic receivers are adopted and provide results with accuracies at the millimeter level: however, they are very expensive and the initial cost and the risk of damage and loss can discourage this approach. In this paper the accuracy and the reliability of low-cost u-blox GNSS receivers are experimentally investigated for local monitoring. Two experiments are analyzed. In the first, a baseline (65 m long) between one geodetic reference receiver and one u-blox is continuously observed for one week: the data are processed by hourly sessions and the results provide comparisons between two processing packages and a preliminary accuracy assessment. Then, a network composed of one geodetic and two u-blox receivers is set up. One u-blox is installed on a device (slide) that allows to apply controlled displacements. The geodetic and the other u-blox (at about 130 m) act as references. The experiment lasts about two weeks. The data are again processed by hourly sessions. The estimated displacements of the u-blox on the slide are analyzed and compared with the imposed displacements. All of the results are encouraging: in the first experiment the standard deviations of the residuals are smaller than 5 mm both in the horizontal and vertical; in the second, they are slightly worse but still satisfactory (5 mm in the horizontal and 13 mm in vertical) and the imposed displacements are almost correctly identified.

Comparison Between Simulations Using the PHITS Code and Activated Material Analysis

In this study, a comparison between simulations using the Particle and Heavy Ion Transport code System (PHITS) code and activated material analysis of JT-60U have been performed. Neutron transport has been simulated using the Monte Carlo method PHITS to determine the neutron fluency at the irradiation position. The activated analysis has been complemented by the foil-activation technique. The preliminary accuracy assessment of these PHITS simulations has been confirmed by comparing the reaction rates of gold, cobalt, and nickel foil activation. The simulation results by PHITS consistent with the measured reaction rate of each foil near the device.

Brief Communication: Low-cost, on-demand aerial photogrammetry for glaciological measurement

Abstract. Remotely sensed glaciological measurements can be expensive, often involving a trade-off between resolution, scale, and frequency. We report on a case study in which two low-cost techniques were used to generate digital elevation models and orthomosaics of an Arctic glacier in consecutive ablation seasons. In the first aerial survey we used an unmanned aerial vehicle and acquired images autonomously. The following year we took advantage of the helicopter used for site access, and were able to acquire images manually, for little additional helicopter time. We present a preliminary assessment of accuracy and apply these data to measure glacier thinning and motion.

Construction of mm‐Level Terrestrial Reference Frame

AbstractIt is noted in this paper that the latest international terrestrial reference frame ITRF2005 cannot satisfy the current need of monitoring mm‐level terrestrial dynamic change. The strategy of using the latest results of ITRF2005, SBL/GGFC (Special Bureau for Loading/Global Geophysical Fluids Center), GRACE and other satellites to construct mm‐level terrestrial reference frame is mentioned in the paper. The methods and some preliminary results for two key problems are introduced: non‐linear characteristic of crust movement and geocenter motion ΔX0(t) monitored using space technology (GPS, VLBI, SLR and GRACE) and modeled by geophysical factors. The preliminary assessment of accuracy and problems in constructing and realizing mm‐level terrestrial reference frame is also introduced.

In-situ Calibration Techniques and Preliminary Assessment of Accuracy for NFM on ITER

Absolutely calibrated measurements of the neutron yields which need to cover both D-D and D-T phase of the international thermal-nuclear experimental reactor (ITER) are important for the evaluation of fusion power and fusion gain Q in D-D and D-T operations. This paper describes the in-situ calibration techniques and methods, the neutron sources including 252Cf and neutron generator for calibration, the preliminary accuracy assessment and the error analyses. In addition, some difficult problems regarding the in situ calibration for the neutron flux monitor (NFM) on ITER are presented and discussed.

A New Mechatronic Assistance System for the Neurosurgical Operating Theatre: Implementation, Assessment of Accuracy and Application Concepts

Objective: To introduce a new robotic system to the field of neurosurgery and report on a preliminary assessment of accuracy as well as on envisioned application concepts. Based on experience with another system (Evolution 1®, URS Inc., Schwerin, Germany), technical advancements are discussed. Material/Methods: The basic module is an industrial 6 degrees of freedom robotic arm with a modified control element. The system combines frameless stereotaxy, robotics, and endoscopy. The robotic reproducibility error and the overall error were evaluated. For accuracy testing CT markers were placed on a cadaveric head and pinpointed with the robot’s tool tip, both fully automated and telemanipulatory. Applicability in a clinical setting, user friendliness, safety and flexibility were assessed. Results: The new system is suitable for use in the neurosurgical operating theatre. Hard- and software are user-friendly and flexible. The mean reproducibility error was 0.052–0.062 mm, the mean overall error was 0.816 mm. The system is less cumbersome and much easier to use than the Evolution 1. Conclusions: With its user-friendly interface and reliable safety features, its high application accuracy and flexibility, the new system is a versatile robotic platform for various neurosurgical applications. Adaptations for different applications are currently being realized.