scholarly journals A Comparative Study of BDS Triple-Frequency Ambiguity Fixing Approaches for RTK Positioning

Sensors ◽  
2021 ◽  
Vol 21 (7) ◽  
pp. 2565
Author(s):  
Huizhong Zhu ◽  
Yangyang Lu ◽  
Longjiang Tang ◽  
Jun Li ◽  
Aigong Xu ◽  
...  
Keyword(s):  
Comparative Study ◽  
Experimental Validation ◽  
Theoretical Explanation ◽  
Normal Equation ◽  
Triple Frequency ◽  
Ambiguity Fixing ◽  
Wide Lane ◽  
Fixed Solution ◽  
The Individual ◽  
Correct Fixing Rate

Concerning the triple-frequency ambiguity resolution, in principle there are three different realizations. The first one is to fix all the ambiguities of the original frequencies together. However, it is also believed that fixing the combined integer ambiguities with longer wavelength, such as extra-wide-lane (EWL), wide-lane (WL), should be advantageous. Also, it is demonstrated that fixing sequentially EWL, WL and one type of original ambiguities provides better results, as the previously fixed ambiguities increase parameters’ precision for later fixings. In this paper, we undertake a comparative study of the three fixing approaches by means of experimental validation. In order to realize the three fixing approaches from the same information in terms of adjustment, we developed a processing strategy to provide fully consistent normal equations. We first generate the normal equation with the original undifferentiated carrier phase ambiguities, then map it into that with the combined and double-differenced ambiguities required by the individual approach for fixing. Four baselines of 258 m, 22 km, 47 km and 53 km are selected and processed in both static and kinematic mode using the three ambiguity-fixing approaches. Indicators including time of first fixed solution (TFFS), the correct fixing rate, positioning accuracy and RATIO are used to evaluate and investigate results. We also made a preliminary theoretical explanation of the results by looking into the decorrelation procedure of the ambiguity searching algorithm and the intermediate results. As conclusions, integrated searching of original ambiguities or combined ambiguities has almost the same fixing performance, whereas the sequential fixing of EWL, WL and B1 ambiguities overperforms the integrated searching. By the way, the third-frequency data can shorten the TFFS significantly but can hardly improve the positioning.

scholarly journals Improving the Stochastic Model of Ionospheric Delays for BDS Long-Range Real-Time Kinematic Positioning

2021 ◽  
Vol 13 (14) ◽  
pp. 2739
Author(s):  
Huizhong Zhu ◽  
Jun Li ◽  
Longjiang Tang ◽  
Maorong Ge ◽  
Aigong Xu
Keyword(s):  
Real Time ◽  
Long Range ◽  
Ionospheric Delay ◽  
Time Interval ◽  
Short Time Interval ◽  
Dual Frequency ◽  
Triple Frequency ◽  
Ambiguity Fixing ◽  
Power Spectral ◽  
Observation Noise

Although ionosphere-free (IF) combination is usually employed in long-range precise positioning, in order to employ the knowledge of the spatiotemporal ionospheric delays variations and avoid the difficulty in choosing the IF combinations in case of triple-frequency data processing, using uncombined observations with proper ionospheric constraints is more beneficial. Yet, determining the appropriate power spectral density (PSD) of ionospheric delays is one of the most important issues in the uncombined processing, as the empirical methods cannot consider the actual ionosphere activities. The ionospheric delays derived from actual dual-frequency phase observations contain not only the real-time ionospheric delays variations, but also the observation noise which could be much larger than ionospheric delays changes over a very short time interval, so that the statistics of the ionospheric delays cannot be retrieved properly. Fortunately, the ionospheric delays variations and the observation noise behave in different ways, i.e., can be represented by random-walk and white noise process, respectively, so that they can be separated statistically. In this paper, we proposed an approach to determine the PSD of ionospheric delays for each satellite in real-time by denoising the ionospheric delay observations. Based on the relationship between the PSD, observation noise and the ionospheric observations, several aspects impacting the PSD calculation are investigated numerically and the optimal values are suggested. The proposed approach with the suggested optimal parameters is applied to the processing of three long-range baselines of 103 km, 175 km and 200 km with triple-frequency BDS data in both static and kinematic mode. The improvement in the first ambiguity fixing time (FAFT), the positioning accuracy and the estimated ionospheric delays are analysed and compared with that using empirical PSD. The results show that the FAFT can be shortened by at least 8% compared with using a unique empirical PSD for all satellites although it is even fine-tuned according to the actual observations and improved by 34% compared with that using PSD derived from ionospheric delay observations without denoising. Finally, the positioning performance of BDS three-frequency observations shows that the averaged FAFT is 226 s and 270 s, and the positioning accuracies after ambiguity fixing are 1 cm, 1 cm and 3 cm in the East, North and Up directions for static and 3 cm, 3 cm and 6 cm for kinematic mode, respectively.

Designing the Person: Sociological Assumptions Embodied within the Architecture of Charles Rennie Mackintosh and Le Corbusier

2005 ◽  
Vol 14 (1) ◽  
pp. 141-162
Author(s):  
Clare Spencer
Keyword(s):  
Social Interaction ◽  
Comparative Study ◽  
Le Corbusier ◽  
Western Society ◽  
Architectural Practice ◽  
Individual Person ◽  
Interesting Insight ◽  
Starting Point ◽  
The Individual ◽  
Insight Into

This essay presents a comparative study of the sociological assumptions implicit, and to some extent explicit, in the work of two famous architects, Charles Rennie Mackintosh and Le Corbusier. The inhabitant implied through the architectural practice of Le Corbusier resembles Elias's homo clausus (closed person), the mode of self experience viewed by Elias as the dominant one in Western society and one which sees the individual person as a ‘thinking subject’ and the starting point of knowledge. Mackintosh's designs, in contrast, imply individual people closer to Elias‘s homines aperti, social beings who are shaped through social interaction and interdependence. This paper demonstrates how, as well as fulfilling social, cultural and political needs, architecture carries, within in its designs, certain assumptions about how people and how they do, and should, live. The adoption of an Eliasian perspective provides an interesting insight into how these assumptions can shape self-experience and social interaction in the buildings of each architect.

scholarly journals A comparative study of functional outcome between platelet rich plasma injection versus steroid infiltration in plantar fasciitis

2020 ◽  
Vol 6 (2) ◽  
pp. 393
Author(s):  
Harpreet Singh ◽  
Malay P. Gandhi ◽  
Aliasgar J. Rampurwala ◽  
Tej S. Rudani
Keyword(s):  
Comparative Study ◽  
Plantar Fasciitis ◽  
Platelet Rich Plasma ◽  
Corticosteroid Injection ◽  
Injection Group ◽  
Plasma Injection ◽  
Significant Difference ◽  
The Difference ◽  
The Individual

<p class="abstract"><strong>Background:</strong> Plantar fasciitis (PF) is considered as degenerative tendinopathies. Repeated micro trauma is the major etiology of these diseases. Autologous platelet rich plasma (PRP) injections are becoming more popular in the treatment of enthesopathies like PF. The growth factors in PRP cause tissue healing. We compared the result of injecting intra-lesional autologous PRP injections versus steroid infiltration in chronic PF.</p><p class="abstract"><strong>Methods:</strong> A prospective, interventional and analytic comparative study was done and 81 patients (120 heels) were included in this study and were followed up for 6 months. We assessed the outcome of each patient using visual analog score (VAS) and foot and ankle disability index (FADI) on follow-up at 1, 3, and 6 months. <strong></strong></p><p class="abstract"><strong>Results:</strong> In our study, female preponderance was seen. Left side was more common as compared to right side. Unilateral PF is more common than bilateral. The difference with in the individual group at baseline and at 1,3 and 6 months was statistically highly significant in terms of VAS and FADI (p=0.0001) But the difference in the between the two groups was insignificant for VAS and FADI at 1, 3 and 6 months.</p><p class="abstract"><strong>Conclusions:</strong> In our study, as there is no significant difference in VAS and FADI score between corticosteroid injection group and PRP injection group at 1, 3 and 6 months follow up. So, it’s reasonable to conclude that both are equally effective in PF. But as PRP injection comes out to be more time consuming and more costly, corticosteroid seems to be more efficient, cost and time wise. Hence, the latter should be a better choice.      </p>

Ileostomy appliances

1969 ◽  
Vol 7 (7) ◽  
pp. 27-28
Keyword(s):  
Comparative Study ◽  
Original Model ◽  
American Patient ◽  
The Subject ◽  
Individual Needs ◽  
The Individual

The management of ileostomy was revolutionised in 1944 when an American patient named Rutzen invented the modern appliance. The original model consisted of a flange and bag in one piece, with a drainage outlet on the bag. Many modifications have since been developed, and a number of manufacturers provide a wide variety of flanges, bags and ancillaries. Choice is dictated mainly by the surgeon’s preferences and the individual needs and preferences of the patient. The subject seems not to lend itself to comparative study, and none has been made.

scholarly journals Real-Time Kinematic Precise Orbit Determination for LEO Satellites Using Zero-Differenced Ambiguity Resolution

2019 ◽  
Vol 11 (23) ◽  
pp. 2815 ◽  
Author(s):  
Xingxing Li ◽  
Jiaqi Wu ◽  
Keke Zhang ◽  
Xin Li ◽  
Yun Xiong ◽  
...  
Keyword(s):  
Real Time ◽  
Ambiguity Resolution ◽  
Orbit Determination ◽  
Precise Orbit Determination ◽  
The Real ◽  
Precise Orbit ◽  
Ambiguity Fixing ◽  
Real Time Kinematic ◽  
Leo Satellites ◽  
Fixed Solution

The rapid growing number of earth observation missions and commercial low-earth-orbit (LEO) constellation plans have provided a strong motivation to get accurate LEO satellite position and velocity information in real time. This paper is devoted to improve the real-time kinematic LEO orbits through fixing the zero-differenced (ZD) ambiguities of onboard Global Navigation Satellite System (GNSS) phase observations. In the proposed method, the real-time uncalibrated phase delays (UPDs) are estimated epoch-by-epoch via a global-distributed network to support the ZD ambiguity resolution (AR) for LEO satellites. By separating the UPDs, the ambiguities of onboard ZD GPS phase measurements recover their integer nature. Then, wide-lane (WL) and narrow-lane (NL) AR are performed epoch-by-epoch and the real-time ambiguity–fixed orbits are thus obtained. To validate the proposed method, a real-time kinematic precise orbit determination (POD), for both Sentinel-3A and Swarm-A satellites, was carried out with ambiguity–fixed and ambiguity–float solutions, respectively. The ambiguity fixing results indicate that, for both Sentinel-3A and Swarm-A, over 90% ZD ambiguities could be properly fixed with the time to first fix (TTFF) around 25–30 min. For the assessment of LEO orbits, the differences with post-processed reduced dynamic orbits and satellite laser ranging (SLR) residuals are investigated. Compared with the ambiguity–float solution, the 3D orbit difference root mean square (RMS) values reduce from 7.15 to 5.23 cm for Sentinel-3A, and from 5.29 to 4.01 cm for Swarm-A with the help of ZD AR. The SLR residuals also show notable improvements for an ambiguity–fixed solution; the standard deviation values of Sentinel-3A and Swarm-A are 4.01 and 2.78 cm, with improvements of over 20% compared with the ambiguity–float solution. In addition, the phase residuals of ambiguity–fixed solution are 0.5–1.0 mm larger than those of the ambiguity–float solution; the possible reason is that the ambiguity fixing separate integer ambiguities from unmodeled errors used to be absorbed in float ambiguities.

Polyclonal Antibody-Based ELISA and HPLC Methods for the Determination of Fumonisins in Corn: A Comparative Study

1996 ◽  
Vol 59 (8) ◽  
pp. 893-897 ◽  
Author(s):  
ERIC W. SYDENHAM ◽  
SONJA STOCKENSTRÖM ◽  
PIETER G. THIEL ◽  
JOHN P. RHEEDER ◽  
M. BRUNO DOKO ◽  
...  
Keyword(s):  
Comparative Study ◽  
Polyclonal Antibody ◽  
High Performance ◽  
Linear Regression Analysis ◽  
Correlation Coefficients ◽  
Hplc Method ◽  
Enzyme Linked Immunosorbent Assay ◽  
Regression Slopes ◽  
The Individual ◽  
The Comparative Study

The performance of an experimental polyclonal antibody (PAb)-based competitive direct enzyme-linked immunosorbent assay (CD-ELISA) developed for the analysis of fumonisins in corn was assessed by comparison with an established high-performance liquid chromatography (HPLC) method. The comparative study was conducted using a series of 20 corn samples naturally contaminated with combined fumonisin levels ranging from &lt;0.05 to &gt;5 μg/g (ppm). Linear regression analysis between the results generated by HPLC and CD-ELISA provided correlation coefficients (r) and regression slopes (b) of r = 0.960, b = 1.493 (P &lt; 0.001); r = 0.865, b = 3.903 (P &lt; 0.001); and r = 0.832, b = 0.107 (P &lt; 0.001) for the individual fumonisins B1 (FB1), B2 (FB2) and B3 (FB3), respectively, while corresponding values of r = 0.967, b = 1.059 (P &lt; 0.001) were obtained for the combined FB1, FB2, and FB3 concentrations. In 3 of 18 fumonisin-positive corn samples, combined fumonisin levels determined by CD-ELISA were between 85 and 100% higher than those determined in the same extracts by HPLC, while in 13 other samples, CD-ELISA results were between 1.8 and 53% higher than those determined by HPLC. Conversely, in 2 of 18 samples, CD-ELISA results were lower than those determined by HPLC. The differences recorded between HPLC and the experimental PAb-based CD-ELISA were far less than those previously recorded for other mono- and polyclonal antibody-based CD-ELISA systems. The results indicate that the experimental PAb-based CD-ELISA may be effectively applied for the initial screening for fumonisins in corn.

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