Preferencje help
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 6

Liczba wyników na stronie
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 1 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników

Wyniki wyszukiwania

help Sortuj według:

help Ogranicz wyniki do:
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 1 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników
Background: The two main factors determining the quality of motion monitoring are the accuracy of determination of position coordinates and the frequency of position logging (fix rate). Material and methods: A comparative analysis of contemporary photogrammetric, remote sensing and satellite methods shows a lack of uniform requirements in this respect with reference to the same sports. Considering the issue on an intuitive basis only, it seems obvious that the accuracy of position in 100-m sprint cannot be measured in metres, and the frequency of positioning should be sub-second. However, the precise values of these variables are not estimated. A mathematical model was created which enabled the determination of minimum requirements concerning athletes’ position accuracy and fix rate, based on statistical data from sports competitions (the results from 4 Olympic Games and 6 World Championships). Results: The key stage for this model is selecting a representative sample of 68% best results (out of a group of results) which is described by time and speed boundary values. Both variables for the selected sport (the 100-m sprint) were calculated: Mmin=0.93 m (minimum position error value) and fmin=10.88 Hz (minimum position fix rate) which enable distinguishing competitors at the finishing line (statistically, position error 5%). Conclusions: (a) The results achieved by sprinters in 100-m run in the world’s best sports events are sufficient to establish requirements regarding the accuracy and the frequency for the determination of athletes’ position in this event. (b) The statistical distribution best fitted to the population of 100-m results is the left-bounded Burr distribution (4P). (c) The method of establishing requirements for the 100-m run should be applied to other track events in order to verify an intuitive perception consisting in the lowering of accuracy and frequency requirements with an increase in an event’s distance.
This paper presents a method which makes it possible to determine reliability characteristics of navigational positioning systems , relevant to an assumed value of permissible error in position fixing. The method allows to calculate : availability , reliability as well as operation continuity of position fixing system for an assumed , determined on the basis of formal requirements - both worldwide and national , position-fixing accuracy. The proposed mathematical model allows to satisfy , by any navigational positioning system , not only requirements as to position-fixing accuracy of a given navigational application ( for air , sea or land traffic ) but also the remaining characteristics associated with technical serviceability of a system. Essence of the method in question consists in the working-out of recorded empirical position-fixing data as well as the making use of multi-state Markov processes ( appropriate to a maximum error value permissible for various navigational applications ) as a result of which reliability characteristics based on real data would be determined. About usefulness of a given navigational positioning system for its possible application would decide a vector of variables (both dealing with position and reliability) which satisfies / or does not satisfy/ formal navigational requirements for a given application
Polish Maritime DGPS system has been modernized to meet the requirements set out in IMO resolution for a future GNSS, but also to preserve backward signal compatibility of user equipment. Having finalized installation of the new technology L1, L2 reference equipment performance tests were performed. This paper presents results of the long-term signal measuring campaign of the DGPS reference station Rozewie, which was performed in July 2009. Final results allowed to verify repeatable and absolute accuracy of the system after the modernization. Obtained statistics were compared to past measurements performed in 2005 when previous system infrastructure was in operation
The accuracy of bathymetric maps, especially in the coastal zone, is very important from the point of view of safety of navigation and transport. Due to the continuous change in shape of the seabed, these maps are fast becoming outdated for precise navigation. Therefore, it is necessary to perform periodical bathymetric measurements to keep them updated on a current basis. At present, none of the institutions in Poland (maritime offices, Hydrographic Office of the Polish Navy) which are responsible for implementation of this type of measurements has at their disposal a hydrographic vessel capable of carrying out measurements for shallow waters (at depths below 1 m). This results in emergence of large areas for which no measurement data have been obtained and, consequently, the maps in the coastal zones are rather unreliable.The article presents the concept of bathymetric measurements for shallow waters with the use of an autonomous, unmanned sur vey vessel (ASV/USV). For this pur pose, the authors modernized a typical ASV/USV unit with standard radio remote control system to the fully autonomous mode. As part of the modernization, the route planning software was created. The developed software works based on, alternatively, GNSS measurements of the coastline, or satellite images. The system was supplemented by an own autopilot (adapted for flying drones). Moreover, the method of controlling electric motors was changed thanks to the use of own electronic circuit.The modernized ASV/USV measuring system was verified by performing bathymetric measurements of the retention reservoir in Gdansk, Poland. Then, the obtained measurement data were used to create a digital bottom model and a bathymetric map of the reservoir
A possibility of utilising the GPS system for navigation and transport are fundamentally dependent on the accuracy in positioning. Two fundamental factors decisive for its value are the values of the User Range Error (URE) and Dilution of Precision (DOP), strictly related to the number of satellites forming the constellation. The nominal constellation of GPS satellites consists of 24 units which gives a possibility of identification of coordinates all over the globe. In the last few years, however, the nominal number of satellites in the constellation was much higher, and the URE value has been constantly increasing. The authors of the paper try to estimate the impact of the changing number of GPS satellites on accuracy of position coordinates with a variable URE value. Mathematical model for estimating geometrical indicators’ value, utilising data derived from the almanac files has been presented. Following a drawn-up algorithm and calculations made with Mathcad software, the authors carried out a comparative analysis of mean daily values of DOP indicators for a variable number of satellites included in the GPS constellation in the years 2001-2013. Then, the authors have established representative values of Two Distance Root Mean Square Error (2drms) 2D and 3D, and calculated a percentage increase of accuracy in the period under discussion
This paper is the fourth in a series of publications presenting the process of installation, testing and long-term assessment of the navigational parameters of the Polish DGPS system. This series of publications intends to present – to the general public – the accomplishments of teams of Polish scientists who have been working for years to make the DGPS the main positioning system used in the Polish sea areas. A considerable part of the materials presented in this paper has never been published.The article presents changes in the position accuracy of the Polish DGPS system over 20 years. Both dynamic tests performed on vessels as well as static measurements campaigns were analysed. The publication contains selected results achieved in its installation and testing in 1995–1997 supplemented with the results of studies conducted in the years: 2006, 2010, 2014, 2017. During this period the position accuracy increased from 2–8 m (1996) to approx. 1–2 m (2010) due to three reasons: turning – off the Selective Availability (2000), technical modernization of reference stations (2010) and continuous – over many years – reducing GPS signal-in-space pseudorange errors, which results in increased position accuracy in all GPS augmentation systems
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 1 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.