scholarly journals Modeling DGNSS Pseudo-Range Correction Messages by Utilizing Satellite Repeat Time

Sensors ◽  
2017 ◽  
Vol 17 (4) ◽  
pp. 834 ◽  
Author(s):  
Dong-Hyo Sohn ◽  
Kwan-Dong Park ◽  
Hyunu Tae
Keyword(s):  
Satellite Repeat ◽  
Repeat Time ◽  
Range Correction

scholarly journals Comparison of Satellite Repeat Shift Time for GPS, BDS, and Galileo Navigation Systems by Three Methods

Algorithms ◽  
2019 ◽  
Vol 12 (11) ◽  
pp. 233 ◽  
Author(s):  
Yanxi Yang ◽  
Jinguang Jiang ◽  
Mingkun Su
Keyword(s):  
Mean Shift ◽  
Navigation Systems ◽  
Maximum Difference ◽  
Satellite Repeat ◽  
Beidou System ◽  
The Status ◽  
Repeat Time ◽  
The Difference ◽  
Gps System ◽  
Global Systems

The characteristic of the satellite repeat shift time can reflect the status of the satellite operation, and is also one of the key factors of the sidereal filtering multipath correction. Although some methods have been developed to calculate the repeat shift time, few efforts have been made to analyze and compare the performance of this feature for the GPS (Global Positioning System), BDS (BeiDou System), and Galileo in depth. Hence, three methods used for calculating the repeat shift time are presented, and used to compare and analyze the three global systems in depth, named the broadcast ephemeris method (BEM), correlation coefficient method (CCM), and aspect repeat time method (ARTM). The experiment results show that the repeat shift time of each satellite is different. Also, the difference between the maximum and minimum varies from different systems. The maximum difference is about 25 s for the BDS IGSO (Inclined Geosynchronous Orbit) and the minimum is merely 10 s for the GPS system. Furthermore, for the same satellite, the shift time calculated by the three methods is almost identical, and the maximum difference is only about 7 s between the CCM and the ARTM method for the BDS MEO (Medium Earth Orbit) satellite. Although the repeat shift time is different daily for the same satellite and the same method, the changes are very small. Moreover, in terms of the STD (Standard Deviation) of the BS (between satellites) and MS (mean shift for the same satellite), the GPS system is the best, the performance of the BDS system is medium, and the Galileo performs slightly worse than the GPS and BDS.

scholarly journals A Single-Difference Multipath Hemispherical Map for Multipath Mitigation in BDS-2/BDS-3 Short Baseline Positioning

2021 ◽  
Vol 13 (2) ◽  
pp. 304
Author(s):  
Chao Liu ◽  
Yuan Tao ◽  
Haiqiang Xin ◽  
Xingwang Zhao ◽  
Chunyang Liu ◽  
...  
Keyword(s):  
Satellite System ◽  
Observation Time ◽  
Double Difference ◽  
Observation Data ◽  
Multipath Mitigation ◽  
Short Baseline ◽  
Independent Variables ◽  
Positioning Errors ◽  
Single Difference ◽  
Repeat Time

The BeiDou Navigation Satellite System (BDS) features a heterogeneous constellation so that it is difficult to mitigate the multipath in the coordinate-domain. Therefore, mitigating the multipath in the observation-domain becomes more important. Sidereal filtering is commonly used for multipath mitigation, which needs to calculate the orbit repeat time of each satellite. However, that poses a computational challenge and damages the integrity at the end of the multipath model. Therefore, this paper proposes a single-difference model based on the multipath hemispherical map (SD-MHM) to mitigate the BDS-2/BDS-3 multipath in a short baseline. The proposed method is converted from double-difference residuals to single-difference residuals, which is not restricted by the pivot satellite transformation. Moreover, it takes the elevation and the azimuth angles of the satellite as the independent variables of the multipath model. The SD-MHM overcomes the unequal observation time of some satellites and does not require specific hardware. The experimental results show that the SD-MHM reduces the root mean square of the positioning errors by 56.4%, 63.9%, and 67.4% in the east, north, and vertical directions; moreover, it contributes to an increase in the baseline accuracy from 1.97 to 0.84 mm. The proposed SD-MHM has significant advantages in multipath mitigation compared with the advanced sidereal filtering method. Besides, the SD-MHM also features an excellent multipath correction capability for observation data with a period of more than seven days. Therefore, the SD-MHM provides a universal strategy for BDS multipath mitigation.

Molecular and Cytological Analyses of Large Tracks of Centromeric DNA Reveal the Structure and Evolutionary Dynamics of Maize Centromeres

Genetics ◽  
2003 ◽  
Vol 163 (2) ◽  
pp. 759-770 ◽  
Author(s):  
Kiyotaka Nagaki ◽  
Junqi Song ◽  
Robert M Stupar ◽  
Alexander S Parokonny ◽  
Qiaoping Yuan ◽  
...  
Keyword(s):  
Evolutionary Dynamics ◽  
Artificial Chromosome ◽  
Grass Species ◽  
Sequence Motifs ◽  
Long Terminal Repeats ◽  
Satellite Repeat ◽  
Sequence Comparisons ◽  
Centromeric Dna ◽  
Conserved Sequence ◽  
Satellite Sequences

Abstract We sequenced two maize bacterial artificial chromosome (BAC) clones anchored by the centromere-specific satellite repeat CentC. The two BACs, consisting of ∼200 kb of cytologically defined centromeric DNA, are composed exclusively of satellite sequences and retrotransposons that can be classified as centromere specific or noncentromere specific on the basis of their distribution in the maize genome. Sequence analysis suggests that the original maize sequences were composed of CentC arrays that were expanded by retrotransposon invasions. Seven centromere-specific retrotransposons of maize (CRM) were found in BAC 16H10. The CRM elements inserted randomly into either CentC monomers or other retrotransposons. Sequence comparisons of the long terminal repeats (LTRs) of individual CRM elements indicated that these elements transposed within the last 1.22 million years. We observed that all of the previously reported centromere-specific retrotransposons in rice and barley, which belong to the same family as the CRM elements, also recently transposed with the oldest element having transposed ∼3.8 million years ago. Highly conserved sequence motifs were found in the LTRs of the centromere-specific retrotransposons in the grass species, suggesting that the LTRs may be important for the centromere specificity of this retrotransposon family.

scholarly journals Global sequence characterization of rice centromeric satellite based on oligomer frequency analysis in large-scale sequencing data

2010 ◽  
Vol 26 (17) ◽  
pp. 2101-2108 ◽  
Author(s):  
Jiří Macas ◽  
Pavel Neumann ◽  
Petr Novák ◽  
Jiming Jiang
Keyword(s):  
Large Scale ◽  
Rice Genome ◽  
Supplementary Information ◽  
Sequencing Data ◽  
Satellite Repeat ◽  
Frequency Spectra ◽  
Consensus Sequences ◽  
Chip Sequencing ◽  
Conserved Sequence ◽  
Centromeric Satellite

Abstract Motivation: Satellite DNA makes up significant portion of many eukaryotic genomes, yet it is relatively poorly characterized even in extensively sequenced species. This is, in part, due to methodological limitations of traditional methods of satellite repeat analysis, which are based on multiple alignments of monomer sequences. Therefore, we employed an alternative, alignment-free, approach utilizing k-mer frequency statistics, which is in principle more suitable for analyzing large sets of satellite repeat data, including sequence reads from next generation sequencing technologies. Results: k-mer frequency spectra were determined for two sets of rice centromeric satellite CentO sequences, including 454 reads from ChIP-sequencing of CENH3-bound DNA (7.6 Mb) and the whole genome Sanger sequencing reads (5.8 Mb). k-mer frequencies were used to identify the most conserved sequence regions and to reconstruct consensus sequences of complete monomers. Reconstructed consensus sequences as well as the assessment of overall divergence of k-mer spectra revealed high similarity of the two datasets, suggesting that CentO sequences associated with functional centromeres (CENH3-bound) do not significantly differ from the total population of CentO, which includes both centromeric and pericentromeric repeat arrays. On the other hand, considerable differences were revealed when these methods were used for comparison of CentO populations between individual chromosomes of the rice genome assembly, demonstrating preferential sequence homogenization of the clusters within the same chromosome. k-mer frequencies were also successfully used to identify and characterize smRNAs derived from CentO repeats. Contact: [email protected] Supplementary information: Supplementary data are available at Bioinformatics online.

scholarly journals Global downscaling of remotely sensed soil moisture using neural networks

2018 ◽  
Vol 22 (10) ◽  
pp. 5341-5356 ◽  
Author(s):  
Seyed Hamed Alemohammad ◽  
Jana Kolassa ◽  
Catherine Prigent ◽  
Filipe Aires ◽  
Pierre Gentine
Keyword(s):  
Soil Moisture ◽  
Spatial Resolution ◽  
Land Surface ◽  
Vegetation Index ◽  
Spatial Scales ◽  
Ancillary Data ◽  
Repeat Time ◽  
Spatiotemporal Scales ◽  
Better Than

Abstract. Characterizing soil moisture at spatiotemporal scales relevant to land surface processes (i.e., of the order of 1 km) is necessary in order to quantify its role in regional feedbacks between the land surface and the atmospheric boundary layer. Moreover, several applications such as agricultural management can benefit from soil moisture information at fine spatial scales. Soil moisture estimates from current satellite missions have a reasonably good temporal revisit over the globe (2–3-day repeat time); however, their finest spatial resolution is 9 km. NASA's Soil Moisture Active Passive (SMAP) satellite has estimated soil moisture at two different spatial scales of 36 and 9 km since April 2015. In this study, we develop a neural-network-based downscaling algorithm using SMAP observations and disaggregate soil moisture to 2.25 km spatial resolution. Our approach uses the mean monthly Normalized Differenced Vegetation Index (NDVI) as ancillary data to quantify the subpixel heterogeneity of soil moisture. Evaluation of the downscaled soil moisture estimates against in situ observations shows that their accuracy is better than or equal to the SMAP 9 km soil moisture estimates.

scholarly journals CENP-B box, a nucleotide motif involved in centromere formation, occurs in a New World monkey

2016 ◽  
Vol 12 (3) ◽  
pp. 20150817 ◽  
Author(s):  
Aorarat Suntronpong ◽  
Kazuto Kugou ◽  
Hiroshi Masumoto ◽  
Kornsorn Srikulnath ◽  
Kazuhiko Ohshima ◽  
...  
Keyword(s):  
Repetitive Dna ◽  
New World ◽  
World Monkey ◽  
Common Marmoset ◽  
Alpha Satellite ◽  
Satellite Repeat ◽  
New World Monkey ◽  
Alpha Satellite Dna ◽  
Negative Results ◽  
Contig Sequence

Centromere protein B (CENP-B) is one of the major proteins involved in centromere formation, binding to centromeric repetitive DNA by recognizing a 17 bp motif called the CENP-B box. Hominids (humans and great apes) carry large numbers of CENP-B boxes in alpha satellite DNA (AS, the major centromeric repetitive DNA of simian primates). Only negative results have been reported regarding the presence of the CENP-B box in other primate taxa. Consequently, it is widely believed that the CENP-B box is confined, within primates, to the hominids. We report here that the common marmoset, a New World monkey, contains an abundance of CENP-B boxes in its AS. First, in a long contig sequence we constructed and analysed, we identified the motif in 17 of the 38 alpha satellite repeat units. We then sequenced terminal regions of additional clones and found the motif in many of them. Immunostaining of marmoset cells demonstrated that CENP-B binds to DNA in the centromeric regions of chromosomes. Therefore, functional CENP-B boxes are not confined to hominids. Our results indicate that the efficiency of identification of the CENP-B box may depend largely on the sequencing methods used, and that the CENP-B box in centromeric repetitive DNA may be more common than researchers previously thought.

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