Analyzing the Precision of Chebyshev Polynomial Fitting GPS Satellite Ephemeris

2013 ◽  
Vol 353-356 ◽  
pp. 3410-3413 ◽  
Author(s):  
Shao Feng Xie ◽  
Peng Fei Zhang ◽  
Li Long Liu
Keyword(s):  
Chebyshev Polynomial ◽  
Interpolation Node ◽  
Polynomial Fitting ◽  
Chebyshev Points ◽  
Precise Ephemeris ◽  
The Difference

Using Chebyshev polynomial to fit precise ephemeris of GPS, the nodes selection has a certain influence on the precision. In this paper we use 3 kinds of precise ephemeris ( IGF, IGR, IGU ) to analyze the difference precision of randomly selected interpolation node and Chebyshev points fitting orbit and compare the difference and precision of fitting orbit by 3 kinds of ephemeris and orbit provided by IGS. The result shows that using Chebyshev points to fit precise ephemeris, the precision of IGF and IGR can achieve mm levels, the precision of IGU can achieve cm levels.

scholarly journals Damage Identification of Bridge Based on Chebyshev Polynomial Fitting and Fuzzy Logic without Considering Baseline Model Parameters

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Yu-Bo Jiao ◽  
Han-Bing Liu ◽  
Yong-Chun Cheng ◽  
Ya-Feng Gong
Keyword(s):  
Fuzzy Logic ◽  
Chebyshev Polynomial ◽  
Damage Identification ◽  
Difference Approximation ◽  
Model Parameters ◽  
Polynomial Fitting ◽  
Fuzzy Logic Systems ◽  
Baseline Model ◽  
Modal Curvature ◽  
Logic Systems

The paper presents an effective approach for damage identification of bridge based on Chebyshev polynomial fitting and fuzzy logic systems without considering baseline model data. The modal curvature of damaged bridge can be obtained through central difference approximation based on displacement modal shape. Depending on the modal curvature of damaged structure, Chebyshev polynomial fitting is applied to acquire the curvature of undamaged one without considering baseline parameters. Therefore, modal curvature difference can be derived and used for damage localizing. Subsequently, the normalized modal curvature difference is treated as input variable of fuzzy logic systems for damage condition assessment. Numerical simulation on a simply supported bridge was carried out to demonstrate the feasibility of the proposed method.

scholarly journals Accuracy Evaluation of Broadcast Ephemeris for BDS-2 and BDS-3

2021 ◽  
Author(s):  
Hao Jun Jian ◽  
Yishi Wang ◽  
Shoujian Zhang
Keyword(s):  
Three Dimensional ◽  
Satellite Orbit ◽  
Earth Observation ◽  
Accuracy Evaluation ◽  
Broadcast Ephemeris ◽  
Clock Error ◽  
Precise Ephemeris ◽  
Geo Satellite ◽  
Detailed Evaluation ◽  
The Difference

Abstract The BDS-3 system was completed in July 2020 and began to provide services to users around the world. The inspection of its operation, especially the detailed evaluation of the orbit, clock error, TGD and other indicators, plays an important role in the subsequent positioning. This study conducts an investigation of the satellite broadcast ephemeris of the BDS-2 and BDS-3. The difference between the satellite orbit position calculated by the broadcast ephemeris and the position calculated by the precise ephemeris is used for analysis. First, the ephemeris form January 2020 to February 2020 are investigated. The results show that the broadcast ephemeris accuracy of the BDS-2 MEO satellite is the highest, while the GEO satellite broadcast ephemeris accuracy is the lowest. And their three-dimensional orbit difference is 3m and 7.5m, respectively. Second, the BDS-3 MEO satellite broadcast ephemeris accuracy is higher than the BDS-2, its three-dimensional orbit accuracy is about 0.39m, while its clock error is slightly smaller than the BDS-2. The result of ephemeris calculation is basically equivalent to the clock error of satellite-to-earth observation, which is related to the addition of the clock error of the inter-satellite link in the BDS-3. Finally, the clock error of the BDS-3 MEO satellite with the H clock is basically the same as that of the MEO satellite with the Rb clock.

Leveling HEM and aeromagnetic data using differential polynomial fitting

Geophysics ◽  
2010 ◽  
Vol 75 (1) ◽  
pp. L13-L23 ◽  
Author(s):  
Majid Beiki ◽  
Mehrdad Bastani ◽  
Laust B. Pedersen
Keyword(s):  
Differential Polynomial ◽  
Average Height ◽  
Aeromagnetic Data ◽  
Polynomial Fitting ◽  
Data Set ◽  
Sliding Windows ◽  
Fitting Method ◽  
Data Points ◽  
The Difference ◽  
Fitting In

We introduce a new technique to level aerogeophysical data. Our approach is applicable to flight-line data without any need for tie-line measurements. The technique is based on polynomial fitting of data points in 1D and 2D sliding windows. A polynomial is fitted to data points in a 2D circular window that contains at least three flight lines. Then the same procedure is done inside a 1D window placed at the center of the 2D window. The leveling error is the difference between 1D and 2D polynomial fitted data at the center of the windows. To demonstrate the reliability of the method, it was tested on a synthetic aeromagnetic data set contaminated by some linear artifacts. Using the differential polynomial fitting method, we can remove the linear artifacts from the data. The method then was applied to two real airborne data sets collected in Iran. The leveling errors are removed effectively from the aeromagnetic data using the differential polynomial fitting. In the case of helicopter-towed electromagnetic (HEM) data, the polynomial fitting method is used to level the measured real (in-phase) and imaginary (quadrature) components, as well as the calculated apparent resistivity. The HEM data are sensitive to height variations, so we introduce an average-height scaling method to reduce the height effect before leveling in-phase and quadrature components. The method also is effective in recovering some of the attenuated anomalies. After scaling, the differential polynomial fitting method was applied to the data and effectively removed the remaining line-to-line artifacts.

The Origin of the Moon

1962 ◽  
Vol 14 ◽  
pp. 149-155 ◽  
Author(s):  
E. L. Ruskol
Keyword(s):  
Chemical Composition ◽  
Solar System ◽  
The Moon ◽  
The Earth ◽  
The Difference ◽  
Origin Of The Moon

The difference between average densities of the Moon and Earth was interpreted in the preceding report by Professor H. Urey as indicating a difference in their chemical composition. Therefore, Urey assumes the Moon's formation to have taken place far away from the Earth, under conditions differing substantially from the conditions of Earth's formation. In such a case, the Earth should have captured the Moon. As is admitted by Professor Urey himself, such a capture is a very improbable event. In addition, an assumption that the “lunar” dimensions were representative of protoplanetary bodies in the entire solar system encounters great difficulties.

Influence of Cell Wall Composition on the Fossilisation of Bacteria and the Implications for the Search for Early Life Forms

1997 ◽  
Vol 161 ◽  
pp. 491-504 ◽  
Author(s):  
Frances Westall
Keyword(s):  
Cell Wall ◽  
Life Forms ◽  
Cation Binding ◽  
Positive Bacterium ◽  
Gram Positive ◽  
Gram Positive Bacteria ◽  
Transmission Electron ◽  
Hydrothermal Sediments ◽  
Identification Of Bacteria ◽  
The Difference

AbstractThe oldest cell-like structures on Earth are preserved in silicified lagoonal, shallow sea or hydrothermal sediments, such as some Archean formations in Western Australia and South Africa. Previous studies concentrated on the search for organic fossils in Archean rocks. Observations of silicified bacteria (as silica minerals) are scarce for both the Precambrian and the Phanerozoic, but reports of mineral bacteria finds, in general, are increasing. The problems associated with the identification of authentic fossil bacteria and, if possible, closer identification of bacteria type can, in part, be overcome by experimental fossilisation studies. These have shown that not all bacteria fossilise in the same way and, indeed, some seem to be very resistent to fossilisation. This paper deals with a transmission electron microscope investigation of the silicification of four species of bacteria commonly found in the environment. The Gram positiveBacillus laterosporusand its spore produced a robust, durable crust upon silicification, whereas the Gram negativePseudomonas fluorescens, Ps. vesicularis, andPs. acidovoranspresented delicately preserved walls. The greater amount of peptidoglycan, containing abundant metal cation binding sites, in the cell wall of the Gram positive bacterium, probably accounts for the difference in the mode of fossilisation. The Gram positive bacteria are, therefore, probably most likely to be preserved in the terrestrial and extraterrestrial rock record.

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