نتایج جستجو برای: gnss
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In natural and urban canyon environments, Global Navigation Satellite System (GNSS) signals suffer from various challenges such as signal multipath, limited or lack of signal availability and poor geometry. Inertial sensors are often employed to improve the solution continuity under poor GNSS signal quality and availability conditions. Various fault detection schemes have been proposed in the l...
Assisted-Global Navigation Satellite Systems (A-GNSS), or Assisted-Global Positioning Systems (A-GPS) in particular, are now commonly accepted as an effective way to reduce the time-to-first-fix (TTFF) in GNSS-unfriendly environments, e.g. in areas of weak GNSS signals. Today’s location-based service (LBS) devices such as GPS-enabled mobile phones and personal digital assistants (PDA) rely on A...
در علوم نقشهبرداری از سامانهی ناوبری ماهوارهای جهانی (GNSS) برای اهداف ژئودتیک و ژئودینامیک استفاده شده است ولی در سالهای اخیر از این سامانه برای اندازهگیری پارامترهای جو کرهی زمین نیز استفاده شده است. یکی از این پارامترها، بخار آب تعلیقپذیر (PWV) اتمسفر میباشد. امکان اندازهگیری PWV توسط گیرندههای GNSS، به واسطهی تأخیر اتمسفری ایجاد شده در سیگنال ارسال شده از طرف ماهواره فراهم میشو...
AUSGeoid09 is the new Australia-wide gravimetric quasigeoid model that has been a posteriori fitted to the Australian Height Datum (AHD) so as to provide a product that is practically useful for the more direct determination of AHD heights from Global Navigation Satellite Systems (GNSS). This approach is necessary because the AHD is predominantly a third-order vertical datum that contains a ~1 ...
Acquiring geospatial data in GNSS compromised environments remains a problem in mapping and positioning in general. Urban canyons, heavily vegetated areas, indoor environments represent different levels of GNSS signal availability from weak to no signal reception. Even outdoors, with multiple GNSS systems, with an ever-increasing number of satellites, there are many situations with limited or n...
Global Navigation Satellite Systems (GNSSs) such as GPS, GLONASS, and the future Galileo and BeiDou, have demonstrated to be a valid and efficient system for various space applications in Low Earth Orbit (LEO), such as spacecraft orbit and attitude determination, rendezvous and formation flight of two or more spacecrafts, and timing synchronization. A GNSS presents a number of significant advan...
Total electron content (TEC) and GNSS positioning error over two Nigeria GNSS stations (CLBR: Latitude; 4.9503°E, Longitude; 8.3514°N, FUTY: Latitude; 9.3497°E, Longitude; 12.4978°N) were studied during the geomagnetic storms of March 17, 2015 minimum Dst (Disturbed storm time) -223nT and that of March 17, 2013 minimum Dst of -132nT (the St. Patrick’s...
11 Driving across unknown routes used to be stressful owing to the almost inevitable problem of getting lost. Thanks to Global Navigation Satellite Systems (GNSS) navigation devices, such problems are now in the past. These devices have revolutionized how we move: they guide us not only in unknown places but also within our own neighbourhoods. Our growing dependence on them to find our way is r...
امروزه با توجه به توسعه و گسترش روزافزون بهکارگیری سامانههای تعیین موقعیت ماهوارهای در دریا، تعیین زاویههای رول (roll)، پیچ (pitch)، و هدینگ (heading یا yaw) شناور با استفاده از گیرندههای GNSS از موضوعات تحقیقاتی مورد توجه در هیدروگرافی است. در این مقاله روشی برای تعیین زاویههای یاد شده بر مبنای سرشکنی کمترین مربعات مورد استفاده و با نصب سه و چهار گیرنده GNSS دو بسامدی جواد با آنتن چو...
In this contribution we analyse the possible nonuniqueness in the least-squares solution of the GNSS carrier-phase compass model. It is shown that this lack of uniqueness may manifest itself in the fixed baseline estimator and therefore in the GNSS compass readings. We present the conditions under which nonuniqueness occurs and give explicit expressions for these nonunique least-squares solutions.
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