observational errors
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MAUSAM ◽  
2021 ◽  
Vol 48 (1) ◽  
pp. 1-8
Author(s):  
BRIJ BHUSHAN

 ABSTRACT. The sector of the eye wall where a spiraling convective barxi a~ars to fasten with it changes and oscillates over the eye wall and such a sector is easily discernible in EnhancOO fufra Red (EIR) imagery received from satellite for a cyclone whose intensity is more than T5.0. It has been argued that a vector having initial point at the centre of the cyclone arxi passing through this particular sector of the eye wall, indicates the future satellite track of a tropical cyclone. The data of the two cyclones. which were showing above mentioned identifiable feawre during a part of their lives. withstood the logic within observational errors.    


2021 ◽  
Vol 24 ◽  
pp. 113-124
Author(s):  
Stephen Gorard ◽  
Yiyi Tan

This paper considers three different claims to knowledge, namely, “fully descriptive”, “generally descriptive” and causal claims. These are all common in social science, and each type of claim requires more assumptions than the previous one. After discussing their methodological and logical foundations, this paper describes some of the limitations in the nature of these three claims. Fully descriptive claims suffer from non-random errors and inaccuracies in observations, and can be queried in terms of utility. Generally, in addition to observational errors, descriptive can be questioned because of the long-standing problem of induction. Even the notion of falsification might not be able to help with this. Finally, causal claims are the most problematic of the three. While widely assumed, causation cannot be observed directly. The paper combines and develops three models of what causation might be, and discusses their implications for causal claims. It points out that so far our belief in causation is still a kind of religious one, and that neither theory nor inferential statistics can help in proving or observing its existence. Finally, the paper provides some suggestions for avoiding being misled by false knowledge and reporting our research findings with tentative care and judgement.


PLoS ONE ◽  
2021 ◽  
Vol 16 (10) ◽  
pp. e0258146
Author(s):  
M. Hou ◽  
M. J. Fagan

As a common feature, bilateral symmetry of biological forms is ubiquitous, but in fact rarely exact. In a setting of analytic geometry, bilateral symmetry is defined with respect to a point, line or plane, and the well-known notions of fluctuating asymmetry, directional asymmetry and antisymmetry are recast. A meticulous scheme for asymmetry assessments is proposed and explicit solutions to them are derived. An investigation into observational errors of points representing the geometric structure of an object offers a baseline reference for asymmetry assessment of the object. The proposed assessments are applicable to individual, part or all point pairs at both individual and collective levels. The exact relationship between the developed treatments and the widely used Procrustes method in asymmetry assessment is examined. An application of the proposed assessments to a large collection of human skull data in the form of 3D landmark coordinates finds: (a) asymmetry of most skulls is not fluctuating, but directional if measured about a plane fitted to shared landmarks or side landmarks for balancing; (b) asymmetry becomes completely fluctuating if one side of a skull could be slightly rotated and translated with respect to the other side; (c) female skulls are more asymmetric than male skulls. The methodology developed in this study is rigorous and transparent, and lays an analytical base for investigation of structural symmetries and asymmetries in a wide range of biological and medical applications.


2021 ◽  
Vol 13 (16) ◽  
pp. 3189
Author(s):  
Min Li ◽  
Tianhe Xu ◽  
Haibo Ge ◽  
Meiqian Guan ◽  
Honglei Yang ◽  
...  

The precise orbit determination (POD) accuracy of the Chinese BeiDou Navigation Satellite System (BDS) is still not comparable to that of the Global Positioning System because of the unfavorable geometry of the BDS and the uneven distribution of BDS ground monitoring stations. Fortunately, low Earth orbit (LEO) satellites, serving as fast moving stations, can efficiently improve BDS geometry. Nearly all studies on Global Navigation Satellite System POD enhancement using large LEO constellations are based on simulations and their results are usually overly optimistic. The receivers mounted on a spacecraft or an LEO satellite are usually different from geodetic receivers and the observation conditions in space are more challenging than those on the ground. The noise level of spaceborne observations needs to be carefully calibrated. Moreover, spaceborne observational errors caused by space weather events, i.e., solar geomagnetic storms, are usually ignored. Accordingly, in this study, the actual spaceborne observation noises are first analyzed and then used in subsequent observation simulations. Then, the observation residuals from the actual-processed LEO POD during a solar storm on 8 September 2017 are extracted and added to the simulated spaceborne observations. The effect of the observational errors on the BDS POD augmented with different LEO constellation configurations is analyzed. The results indicate that the noise levels from the Swarm-A, GRACE-A, and Sentinel-3A satellites are different and that the carrier-phase measurement noise ranges from 2 mm to 6 mm. Such different noise levels for LEO spaceborne observations cause considerable differences in the BDS POD solutions. Experiments calculating the augmented BDS POD for different LEO constellations considering spaceborne observational errors extracted from the solar storm indicate that these errors have a significant influence on the accuracy of the BDS POD. The 3D root mean squares of the BDS GEO, IGSO, and MEO satellite orbits are 1.30 m, 1.16 m, and 1.02 m, respectively, with a Walker 2/1/0 LEO constellation, and increase to 1.57 m, 1.72 m, and 1.32 m, respectively, with a Walker 12/3/1 constellation. When the number of LEO satellites increases to 60, the precision of the BDS POD improves significantly to 0.89 m, 0.77 m, and 0.69 m for the GEO, IGSO, and MEO satellites, respectively. While 12 satellites are sufficient to enhance the BDS POD to the sub-decimeter level, up to 60 satellites can effectively reduce the influence of large spaceborne observational errors, i.e., from solar storms.


2021 ◽  
Vol 57 (2) ◽  
pp. 181-190

Experimental results on the absorption of ultrasound by a magnetic fluid in a rotating magnetic field have been obtained for the first time. It is shown that the lag of the angular dependence of the ultrasonic absorption coefficient by a magnetic fluid in the range of magnetic field rotation frequencies fH = 0.056 - 280 mHz at T = 295 K is not observed within the limits of observational errors. Similar results were observed for both low-viscosity and high-viscosity magnetic fluids. Tables 1, Figs 6, Refs 39.


Mathematics ◽  
2021 ◽  
Vol 9 (12) ◽  
pp. 1445
Author(s):  
Rodi Lykou ◽  
George Tsaklidis

Observational errors of Particle Filtering are studied over the case of a state-space model with a linear observation equation. In this study, the observational errors are estimated prior to the upcoming observations. This action is added to the basic algorithm of the filter as a new step for the acquisition of the state estimations. This intervention is useful in the presence of missing data problems mainly, as well as sample tracking for impoverishment issues. It applies theory of Homogeneous and Non-Homogeneous closed Markov Systems to the study of particle distribution over the state domain and, thus, lays the foundations for the employment of stochastic control against impoverishment. A simulating example is quoted to demonstrate the effectiveness of the proposed method in comparison with existing ones, showing that the proposed method is able to combine satisfactory precision of results with a low computational cost and provide an example to achieve impoverishment prediction and tracking.


2021 ◽  
Author(s):  
Lucy Marshall

<div> <p>The latest generation of integrated hydrologic models provides new opportunities to better understand and hypothesize about the connections between hydrological, ecological and energy transfer processes across a range of scales. Parallel to this has been unprecedented growth in new technologies to observe components of Earth’s biophysical system through satellite remote sensing or on-the-ground instruments. However, along with growth in available data and advanced modelling platforms comes a challenge to ensure models are representative of catchment systems and are not unrealistically confident in their predictions. Many hydrologic and ecosystem variables are measured infrequently, measured with significant error, or are measured at a scale different to their representation in a model. In fact, the modelled variable of interest is frequently not directly observed but inferred from surrogate measurements. This introduces errors in model calibration that will affect whether our models are representative of the systems we seek to understand.</p> </div><div> <p>In recent years, Bayesian inference has emerged as a powerful tool in the environmental modeler’s toolbox, providing a convenient framework in which to model parameter and observational uncertainties. The Bayesian approach is ideal for multivariate model calibration, by defining proper prior distributions that can be considered analogous to the weighting often prescribed in traditional multi-objective calibration. </p> </div><div> <p>In this study, we develop a multi-objective Bayesian approach to hydrologic model inference that explicitly capitalises on a priori knowledge of observational errors to improve parameter estimation and uncertainty estimation. We introduce a novel error model, which partitions observation and model residual error according to prior knowledge of the estimated uncertainty in the calibration data. We demonstrate our approach in two case studies: an ecohydrologic model where we make use of the known uncertainty in satellite retrievals of Leaf Area Index (LAI), and a water quality model using turbidity as a proxy for Total Suspended Solids (TSS). Overall, we aim to demonstrate the need to properly account for known observational errors in proper hydrologic model calibration.</p> </div>


2021 ◽  
Vol 503 (2) ◽  
pp. 1877-1883
Author(s):  
Amy Bonsor ◽  
Paula Jofré ◽  
Oliver Shorttle ◽  
Laura K Rogers ◽  
Siyi Xu(许偲艺) ◽  
...  

ABSTRACT Planets and stars ultimately form out of the collapse of the same cloud of gas. Whilst planets, and planetary bodies, readily loose volatiles, a common hypothesis is that they retain the same refractory composition as their host star. This is true within the Solar system. The refractory composition of chondritic meteorites, Earth, and other rocky planetary bodies are consistent with solar, within the observational errors. This work aims to investigate whether this hypothesis holds for exoplanetary systems. If true, the internal structure of observed rocky exoplanets can be better constrained using their host star abundances. In this paper, we analyse the abundances of the K-dwarf, G200-40, and compare them to its polluted white dwarf companion, WD 1425+540. The white dwarf has accreted planetary material, most probably a Kuiper belt-like object, from an outer planetary system surviving the star’s evolution to the white dwarf phase. Given that binary pairs are chemically homogeneous, we use the binary companion, G200-40, as a proxy for the composition of the progenitor to WD 1425+540. We show that the elemental abundances of the companion star and the planetary material accreted by WD 1425+540 are consistent with the hypothesis that planet and host-stars have the same true abundances, taking into account the observational errors.


Author(s):  
I. N. Nikonorov ◽  
◽  
Ya. Zhuchkov ◽  

This work is devoted to study of transformations equations between Binstr, Ginstr, Rinstr photometric system of 28-cm Schmidt-Cassegrain telescope mounted in NCAS KFU to standard Johnson—Cousins BJ , VJ , RC using modern numerical methods. Observations of Landold Standards at the SA110 region were performed. Absolute photometry of selected stars was obtained with estimatiuon of observational errors. To transform the observational data into the standart system numerical model was built with the use of Markov Chain Monte Carlo sampling. So, we found average parameters of transformations between systems (color reduction coefficients are 0.165, −0.120, −0.378 for B0 J , V 0 J , R0C in dependence of (B − G)0 instr, (G − R)0 instr, (G − R)0 instr respectievely) and medium extinction at the observational period (0.276, 0.205, 0.159 for Binstr, Ginstr, Rinstr respectievely).


2020 ◽  
Vol 644 ◽  
pp. A51
Author(s):  
N. C. Santos ◽  
E. Cristo ◽  
O. Demangeon ◽  
M. Oshagh ◽  
R. Allart ◽  
...  

Context. The detection and characterization of exoplanet atmospheres is currently one of the main drivers pushing the development of new observing facilities. In this context, high-resolution spectrographs are proving their potential and showing that high-resolution spectroscopy will be paramount in this field. Aims. We aim to make use of ESPRESSO high-resolution spectra, which cover two transits of HD 209458b, to probe the broadband transmission optical spectrum of the planet. Methods. We applied the chromatic Rossiter–McLaughin method to derive the transmission spectrum of HD 209458b. We compared the results with previous HST observations and with synthetic spectra. Results. We recover a transmission spectrum of HD 209458b similar to the one obtained with HST data. The models suggest that the observed signal can be explained by only Na, only TiO, or both Na and TiO, even though none is fully capable of explaining our observed transmission spectrum. Extra absorbers may be needed to explain the full dataset, though modeling approximations and observational errors can also be responsible for the observed mismatch. Conclusions. Using the chromatic Rossiter–McLaughlin technique, ESPRESSO is able to provide broadband transmission spectra of exoplanets from the ground, in conjunction with space-based facilities, opening good perspectives for similar studies of other planets.


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