This paper summarizes the contribution of Polish scientific units to the development of the Global Geodetic Observing System (GGOS) in recent years. We discuss the issues related to the integration of space geodetic techniques and co-location in space onboard Global Navigation Satellites Systems (GNSS) and Low Earth Orbiters (LEO), as well as perspectives introduced by the new European Space Agency’s (ESA) mission GENESIS. We summarize recent developments in terms of the European Galileo system and its contribution to satellite geodesy and general relativity, as well as ESA’s recent initiative – Moonlight to establish a satellite navigation and communication system for the Moon. Recent progress in troposphere delay modeling in Satellite Laser Ranging (SLR) allowed for better handling of systematic errors in SLR, such as range biases and tropospheric biases. We discuss enhanced tropospheric delay models for SLR based on numerical weather models with empirical corrections, which improve the consistency between space geodetic parameters derived using different techniques, such as SLR, GNSS, and Very Long Baseline Interferometry (VLBI). Finally, we review recent progress in the development of Polish GGOS scientific infrastructure in the framework of the European Plate Observing System project EPOS-PL.
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This article presents a system of precise navigation for a visually impaired person which uses GPS navigation and an infrared sensor in the form of an infrared matrix. The presented system allows determining the orientation and distance of a blind person relative to a selected object, e.g. a wall or road edge. The application of the above solution facilitates a significant increase in the accuracy of determining the position of a blind person compared to the accuracy offered by commonly used ground satellite devices. The system uses thermal energy accumulated in the environment without the need to generate additional signals. The main parts of the system are a simple infrared matrix, data processing system and vibrating wristband. Messages and navigation warnings are sent to a blind person in the form of a vibration code. The article describes the method of determining the path of a specified width and distance from the wall of a building, curb, etc., along which a blind person should move. The article additionally describes the method of determining the orientation of a blind person depending on the selected object. Such a method facilitates verifying whether the visually impaired person is moving according to the indicated direction. The method can also be used to navigate mobile robots. Due to the use of natural energy for data registration and processing, the mobile navigation system can be operated for a long time without the need to recharge the battery.
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W nocy z 6 na 7 kwietnia 2019 r. (z soboty na niedzielę), o godz. 2:00 czasu urzędowego nastąpiło wyzerowanie się 10-bitowego licznika numerów tygodni (przepełnienie licznika), wysyłanego w depeszy nawigacyjnej przez satelity systemu nawigacji satelitarnej GPS (Global Positioning System). Oznacza to, że po numerze tygodnia „1023” (2 do potęgi 10 minus 1), liczonego w systemie GPS w sposób ciągły od daty 22 sierpnia 1999 r., nastąpił numer „0”, który odpowiada pierwszemu tygodniowi liczonemu już od daty 7 kwietnia 2019 r. Zdarzenie takie, nazywane „GPS week number rollover”, wywoływało pewne obawy wśród przedstawicieli branży związanej z synchronizacją czasu i częstotliwości. W pewnym stopniu potwierdziły się one w rzeczywistości.
EN
At the night from 6 to 7 April 2019 at 2:00 am (UTC), the GPS (Global Positioning System) experienced a 10-bits week counter roll over to zero (data storage overflow). This counter is included in the satellite-transmitted navigation message. In view of the above, week number “1023” (2 to the power of 10 minus 1), calculated in the GPS system continuously from 22 August 1999, is followed by the number “0”, which corresponds to the first week counted from 7 April 2019. This event is called “GPS week number rollover” and was preceded by concerns manifested among representatives of the industry associated time and frequency synchronization. Some of these fears were confirmed in reality.
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Audio communication on the public Internet suffers from not synchronized word clocks of the involved audio devices. The resulting clock drift leads to audio dropouts, which is typically compensated by a sample rate conversion (SRC) in standard telecommunication systems. This, however, does not fulfill the requirements of a high-quality audio system, in which all devices share one and the same word clock. Professional IP based network audio systems such as DANTE or AVB with their respective clock synchronization techniques have so been limited to LAN usage, where network jitter and loss have negligible importance regarding the required accuracy in the dimension of several nanoseconds. In a WAN, however, jitter in the millisecond dimension would lead to unacceptable measurement errors for the intended clock synchronization. As a consequence, we decided to investigate alternative clock synchronization techniques for WAN-distributed devices and developed a GNSS-based approach, which leads to precise clock synchronization.
Od momentu przystąpienia Polski do Europejskiej Agencji Kosmicznej, zainteresowanie krajowych firm i instytucji segmentem technik i systemów satelitarnych znacząco wzrosło. W niniejszym artykule opisano działania Instytutu Łączności – Państwowego Instytutu Badawczego (IŁ) na tym polu na przestrzeni kilku ostatnich lat. Poszczególne części publikacji poświęcone są osobnym obszarom tematycznym podejmowanym przez IŁ, w tym: badaniom dostępności sygnałów GNSS na terenie Polski, standaryzacji i rozwojowi nowego systemu łączności na morzu VDES, pracom związanym z opracowaniem koncepcji polskiego satelity AIS/VDES oraz metrologii czasu.
EN
Ever since Poland become a member of the European Space Agency, the involvement of Polish entities in the area of satellites systems and techniques has significantly increased. This article presents the recent activity of National Institute of Telecommunications (NIT) in this field. Every section of the paper is dedicated to a specific topic the NIT dealt with in the last few years, including: the measurements of the GNSS signal availability in Poland, the standardization and analysis of the novel maritime communication system VDES, feasibility study of the Polish AIS/VDES satellite and the metrology of time.
Twenty four hour GNSS (Global Navigation Satellite System) data acquired monthly for 5 years from 8 CORS (Continuously Operating Reference Station) stations in Central Valley, California are processed and vertical velocities of the points are determined. To process GNSS data, online GNSS data processing service APPS (Automatic Precise Positioning Service) is used. GNSS data downloaded from NGS (National Geodetic Survey) CORS are analyzed and subsidence at these points is portrayed with graphics. It is revealed that elevation changes range from 5 mm uplift in the north to 163 mm subsidence in the southern part of the valley.
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