scholarly journals Enhanced wide-area multi-GNSS RTK and rapid static positioning in the presence of ionospheric disturbances

2020 ◽  
Vol 72 (1) ◽  
Author(s):  
Jacek Paziewski ◽  
Rafal Sieradzki
2016 ◽  
Vol 58 (6) ◽  
Author(s):  
Rafal Sieradzki ◽  
Jacek Paziewski

<p>Total electron content (TEC) fluctuation in the ionosphere is one of the main unresolved problems degrading ambiguity resolution and thus affect the reliability of satellite positioning. With regard to conditions prevailing at mid-latitudes, the impact of the upper atmospheric layers is primarily associated with the occurrence of medium-scale traveling ionospheric disturbances (MSTIDs). This study contains the combined analysis involving MSTIDs patterns observed in raw phase data and their impact on rapid static positioning. The first part is aimed at discrepancies in wavelike MSTIDs signatures detected in time series of high elevated measurements. It was demonstrated that the differences in slant ionospheric delays at medium baselines often exceed 0.5 TEC units and more importantly, the detected MSTIDs patterns were highly mutable. The next section presents the impact of MSTIDs on double differenced ionospheric delays and performance of rapid static positioning. The positioning was executed using two approaches. The first one adopted as a benchmark strategy was the geometry-based relative positioning model with weighted ionosphere and troposphere parametrization. The second approach was the improved version of the former. It used the rate of TEC corrections, which allowed the mitigation of MSTIDs through the reduction of epoch-wise ionospheric delays to one parameter for each double-differenced arc. The comparison of results for both strategies indicated significant improvement of positioning performance after the application of proposed algorithm.</p>


Author(s):  
D. E. Becker

An efficient, robust, and widely-applicable technique is presented for computational synthesis of high-resolution, wide-area images of a specimen from a series of overlapping partial views. This technique can also be used to combine the results of various forms of image analysis, such as segmentation, automated cell counting, deblurring, and neuron tracing, to generate representations that are equivalent to processing the large wide-area image, rather than the individual partial views. This can be a first step towards quantitation of the higher-level tissue architecture. The computational approach overcomes mechanical limitations, such as hysterisis and backlash, of microscope stages. It also automates a procedure that is currently done manually. One application is the high-resolution visualization and/or quantitation of large batches of specimens that are much wider than the field of view of the microscope.The automated montage synthesis begins by computing a concise set of landmark points for each partial view. The type of landmarks used can vary greatly depending on the images of interest. In many cases, image analysis performed on each data set can provide useful landmarks. Even when no such “natural” landmarks are available, image processing can often provide useful landmarks.


Author(s):  
K. K. Christenson ◽  
J. A. Eades

One of the strengths of the Philips EM-400 series of TEMs is their ability to operate under two distinct optical configurations: “microprobe”, the normal TEM operating condition which allows wide area illumination, and “nanoprobe”, which gives very small probes with high angular convergence for STEM imaging, microchemical and microstructural analyses. This change is accomplished by effectively turning off the twin lens located in the upper pole piece which changes the illumination from a telefocus system to a condenser-objective system. The deflection and tilt controls and alignments are designed for microprobe use and do not function properly when in nanoprobe. For instance, in nanoprobe the deflection control gives a mix of deflection and tilt; as does the tilt control.


1998 ◽  
Vol 4 (5-6) ◽  
pp. 56-61 ◽  
Author(s):  
A.P. Vereshak ◽  
◽  
A.A. Zhalilo ◽  
I.G. Nozdrin ◽  
S.N. Flerko ◽  
...  
Keyword(s):  

2011 ◽  
Vol 131 (7) ◽  
pp. 536-541 ◽  
Author(s):  
Tarek Hassan Mohamed ◽  
Abdel-Moamen Mohammed Abdel-Rahim ◽  
Ahmed Abd-Eltawwab Hassan ◽  
Takashi Hiyama

Sign in / Sign up

Export Citation Format

Share Document