78 research outputs found

    Precise indoor positioning with pseudolites : iRTK, iPPP and iPPP-RTK

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    A pseudolite (PL) is a ground-based positioning system that offers flexible deployment and accurate โ€œorbitsโ€. The PL system can carry on the role of the GNSS to provide precise positioning for indoor users. However, there are some unusual challenges that seriously affect the performance of a PL system in precise indoor positioning. To raise PL-based positioning accuracy up to the centimeter level or higher, the use of the PL carrier phase measurement with ambiguity resolution is a unique consideration. The PL phase ambiguities are also contaminated by clock bias, multipath errors, and cycle clips. Their existence destroys the integer nature of ambiguity and impedes the pursuit of further accuracy improvement. The major contributions in this research for addressing the above-mentioned challenging issues are specified as follows: 1. The ground-based AR methods are discussed. The impact of ground-based geometry on indoor AR is researched, and the influence of linearization error is also investigated. An efficient PL-based AR method is studied and verified in the balance of gaining convenience and avoiding linearization impact. 2. The clock bias between PL transmitters can be properly handled in a way that time synchronization can be achieved with a transmitter-only PL system at low cost and simplicity. Therefore, the PL-based the ambiguities are able to be fixed to correct integers, and centimeter-level indoor precise positioning can be reliably achieved. In addition, the proposed way for time synchronization is also applicable for other ground-based systems for precise positioning purposes. 3. The stochastic model for mitigation of indoor multipath and NLOS is investigated. The experimental results demonstrate that the proposed stochastic model is superior to other existing models in indoor multipath mitigation as it is competent to suppress the multipath errors mainly caused by multipath to the smallest in both static and kinematic results, respectively. Moreover, it is also verified to be efficient for NLOS mitigation. With the proposed new stochastic model, precise point positioning is confidently expected indoors. 4. The methods for PL-based cycle slips are extensively studied and discussed. Numerical results indicate that the integer-cycle slips can be efficiently and accurately detected and corrected. The concern about PL-based cycle slip is minimized, the reliability and sustainability of PL-based precise indoor positioning can be promised

    Contributions to Positioning Methods on Low-Cost Devices

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    Global Navigation Satellite System (GNSS) receivers are common in modern consumer devices that make use of position information, e.g., smartphones and personal navigation assistants. With a GNSS receiver, a position solution with an accuracy in the order of five meters is usually available if the reception conditions are benign, but the performance degrades rapidly in less favorable environments and, on the other hand, a better accuracy would be beneficial in some applications. This thesis studies advanced methods for processing the measurements of low-cost devices that can be used for improving the positioning performance. The focus is on GNSS receivers and microelectromechanical (MEMS) inertial sensors which have become common in mobile devices such as smartphones. First, methods to compensate for the additive bias of a MEMS gyroscope are investigated. Both physical slewing of the sensor and mathematical modeling of the bias instability process are considered. The use of MEMS inertial sensors for pedestrian navigation indoors is studied in the context of map matching using a particle filter. A high-sensitivity GNSS receiver is used to produce coarse initialization information for the filter to decrease the computational burden without the need to exploit local building infrastructure. Finally, a cycle slip detection scheme for stand-alone single-frequency GNSS receivers is proposed. Experimental results show that even a MEMS gyroscope can reach an accuracy suitable for North seeking if the measurement errors are carefully modeled and eliminated. Furthermore, it is seen that even a relatively coarse initialization can be adequate for long-term indoor navigation without an excessive computational burden if a detailed map is available. The cycle slip detection results suggest that even small cycle slips can be detected with mass-market GNSS receivers, but the detection rate needs to be improved

    Benefits from a multi-receiver architecture for GNSS precise positioning

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    Precise positioning with a stand-alone GPS receiver or using differential corrections is known to be strongly degraded in an urban or sub-urban environment due to frequent signal masking, strong multipath effect, frequent cycle slips on carrier phase, etc. The objective of this Ph.D. thesis is to explore the possibility of achieving precise positioning with a low-cost architecture using multiple installed low-cost single-frequency receivers with known geometry whose one of them is RTK positioned w.r.t an external reference receiver. This setup is thought to enable vehicle attitude determination and RTK performance amelioration. In this thesis, we firstly proposed a method that includes an array of receivers with known geometry to enhance the performance of the RTK in different environments. Taking advantage of the attitude information and the known geometry of the installed array of receivers, the improvement of some internal steps of RTK w.r.t an external reference receiver can be achieved. The navigation module to be implemented in this work is an Extended Kalman Filter (EKF). The performance of a proposed two-receiver navigation architecture is then studied to quantify the improvements brought by the measurement redundancy. This concept is firstly tested on a simulator in order to validate the proposed algorithm and to give a reference result of our multi-receiver systemโ€™s performance. The pseudorange measurements and carrier phase measurements mathematical models are implemented in a realistic simulator. Different scenarios are conducted, including varying the distance between the 2 antennas of the receiver array, the satellite constellation geometry, and the amplitude of the noise measurement, in order to determine the influence of the use of an array of receivers. The simulation results show that our multi-receiver RTK system w.r.t an external reference receiver is more robust to noise and degraded satellite geometry, in terms of ambiguity fixing rate, and gets a better position accuracy under the same conditions when compared with the single receiver system. Additionally, our method achieves a relatively accurate estimation of the attitude of the vehicle which provides additional information beyond the positioning. In order to optimize our processing, the correlation of the measurement errors affecting observations taken by our array of receivers has been determined. Then, the performance of our real-time single frequency cycle-slip detection and repair algorithm has been assessed. These two investigations yielded important information so as to tune our Kalman Filter. The results obtained from the simulation made us eager to use actual data to verify and improve our multi-receiver RTK and attitude system. Tests based on real data collected around Toulouse, France, are used to test the performance of the whole methodology, where different scenarios are conducted, including varying the distance between the 2 antennas of the receiver array as well as the environmental conditions (open sky, suburban, and constrained urban environments). The thesis also tried to take advantage of a dual GNSS constellation, GPS and Galileo, to further strengthen the position solution and the reliable use of carrier phase measurements. The results show that our multi-receiver RTK system is more robust to degraded GNSS environments. Our experiments correlate favorably with our previous simulation results and further support the idea of using an array of receivers with known geometry to improve the RTK performance

    Localization Precise in Urban Area

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    Nowadays, stand-alone Global Navigation Satellite System (GNSS) positioning accuracy is not sufficient for a growing number of land users. Sub-meter or even centimeter accuracy is becoming more and more crucial in many applications. Especially for navigating rovers in the urban environment, final positioning accuracy can be worse as the dramatically lack and contaminations of GNSS measurements. To achieve a more accurate positioning, the GNSS carrier phase measurements appear mandatory. These measurements have a tracking error more precise by a factor of a hundred than the usual code pseudorange measurements. However, they are also less robust and include a so-called integer ambiguity that prevents them to be used directly for positioning. While carrier phase measurements are widely used in applications located in open environments, this thesis focuses on trying to use them in a much more challenging urban environment. To do so, Real Time-Kinematic (RTK) methodology is used, which is taking advantage on the spatially correlated property of most code and carrier phase measurements errors. Besides, the thesis also tries to take advantage of a dual GNSS constellation, GPS and GLONASS, to strengthen the position solution and the reliable use of carrier phase measurements. Finally, to make up the disadvantages of GNSS in urban areas, a low-cost MEMS is also integrated to the final solution. Regarding the use of carrier phase measurements, a modified version of Partial Integer Ambiguity Resolution (Partial-IAR) is proposed to convert as reliably as possible carrier phase measurements into absolute pseudoranges. Moreover, carrier phase Cycle Slip (CS) being quite frequent in urban areas, thus creating discontinuities of the measured carrier phases, a new detection and repair mechanism of CSs is proposed to continuously benefit from the high precision of carrier phases. Finally, tests based on real data collected around Toulouse are used to test the performance of the whole methodology

    Pseudolite/Ultra Low-Cost IMU Integrated Robust Indoor Navigation System through Real-time Cycle Slip Detection and Compensation

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    ํ•™์œ„๋…ผ๋ฌธ (์„์‚ฌ)-- ์„œ์šธ๋Œ€ํ•™๊ต ๋Œ€ํ•™์› ๊ณต๊ณผ๋Œ€ํ•™ ๊ธฐ๊ณ„ํ•ญ๊ณต๊ณตํ•™๋ถ€, 2017. 8. ๊ธฐ์ฐฝ๋ˆ.GNSS๋ฅผ ํ†ตํ•œ ํ•ญ๋ฒ•์ด ํ™œ์„ฑํ™” ๋˜๋ฉด์„œ GNSS ํ•ญ๋ฒ•์ด ๋ถˆ๊ฐ€๋Šฅํ•œ ์‹ค๋‚ด์—์„œ์˜ ํ•ญ๋ฒ•์— ๋Œ€ํ•œ ํ•„์š”์„ฑ ์—ญ์‹œ ์ฆ๊ฐ€ํ•˜๊ณ  ์žˆ๋‹ค. ํ•˜์ง€๋งŒ ์‹ค๋‚ด ํ™˜๊ฒฝ์˜ ๊ฒฝ์šฐ ํ•ญ๋ฒ•์„ ์ˆ˜ํ–‰ํ•จ์— ์žˆ์–ด ๋ฐฉํ•ด๊ฐ€ ๋˜๋Š” ์š”์†Œ๋“ค์ด ๋งŽ๊ธฐ ๋•Œ๋ฌธ์— ์•„์ง ํ™•์‹คํ•˜๋‹ค๊ณ  ํ•  ์ˆ˜ ์žˆ๋Š” ์‹ค๋‚ดํ•ญ๋ฒ•์‹œ์Šคํ…œ์€ ๊ฐœ๋ฐœ๋˜์–ด ์žˆ์ง€ ์•Š๋‹ค. ์ด์— ๋”ฐ๋ผ ์›ํ™œํ•œ ์‹ค๋‚ด ํ•ญ๋ฒ• ์‹œ์Šคํ…œ์„ ๊ฐœ๋ฐœํ•˜๊ธฐ ์œ„ํ•ด ํ˜„์žฌ RFID, Wi-Fi, Visual Sensor, IMU ๊ทธ๋ฆฌ๊ณ  ์˜์‚ฌ์œ„์„ฑ ๋“ฑ ๋‹ค์–‘ํ•œ ๋ฐฉ์‹์˜ ์—ฐ๊ตฌ๋“ค์ด ์ง„ํ–‰๋˜๊ณ  ์žˆ๋‹ค. ๊ทธ ์ค‘ ๋†’์€ ์ •ํ™•๋„์˜ ์œ„์น˜๊ฒฐ๊ณผ๋ฅผ ์–ป์„ ์ˆ˜ ์žˆ๋Š” ์˜์‚ฌ์œ„์„ฑ ๋ฐ˜์†กํŒŒ ์‹ ํ˜ธ์™€ ์ €๊ฐ€์˜ IMU ๊ทธ๋ฆฌ๊ณ  Magnetometer์˜ ๊ฒฐํ•ฉ์„ ํ†ตํ•ด ์‹ค๋‚ด ํ•ญ๋ฒ•์„ ์‹œ๋„ํ•˜์˜€๋˜ ์—ฐ๊ตฌ๊ฐ€ ์กด์žฌํ•˜์˜€๋‹ค. ํ•˜์ง€๋งŒ ์ด ๊ฒฝ์šฐ ๋ฐ˜์†กํŒŒ์˜ ์‚ฌ์ดํด ์Šฌ๋ฆฝ ๋ฐœ์ƒ ๋ฌธ์ œ๊ฐ€ ๋‚จ์•„ ์žˆ์—ˆ๊ธฐ ๋•Œ๋ฌธ์— ํ•ญ๋ฒ•์—๋Š” ์ œํ•œ์ด ์žˆ์—ˆ๋‹ค. ๋˜ ๋‹ค๋ฅธ ์—ฐ๊ตฌ๋กœ๋Š” ์‹ค์™ธ์—์„œ GPS์™€ IMU์˜ ๊ฒฐํ•ฉ์„ ํ†ตํ•ด ์‚ฌ์ดํด ์Šฌ๋ฆฝ์„ ๊ฒ€์ถœ ๋ฐ ๋ณด์ƒํ•œ ์—ฐ๊ตฌ๊ฐ€ ์žˆ์—ˆ๋‹ค. ์ด๋Š” ์‹ค์™ธํ™˜๊ฒฝ์—์„œ ์ง„ํ–‰๋œ ์—ฐ๊ตฌ๋กœ์จ 1 ์‚ฌ์ดํด ๋‹จ์œ„์˜ ์Šฌ๋ฆฝ ๋งŒ ๊ฒ€์ถœ ๊ฐ€๋Šฅํ•˜์˜€๋‹ค. ๊ทธ๋Ÿฐ๋ฐ ์‹ค๋‚ดํ™˜๊ฒฝ์—์„œ๋Š” ์‚ฌ์ดํด ์Šฌ๋ฆฝ ๋ฐœ์ƒ๋ฅ ์ด ๋” ๋†’์•„ ํ•˜ํ”„ ์‚ฌ์ดํด ๋‹จ์œ„์˜ ์Šฌ๋ฆฝ๊นŒ์ง€๋„ ์ž์ฃผ ๋ฐœ์ƒํ•˜๊ธฐ ๋•Œ๋ฌธ์— ์‹ค๋‚ดํ•ญ๋ฒ•์—์„œ๋Š” ์ด๋ฅผ ๊ทธ๋Œ€๋กœ ์ ์šฉํ•  ์ˆ˜ ์—†์—ˆ๋‹ค. ๋ณธ ์—ฐ๊ตฌ์—์„œ๋Š” ์œ„์˜ ๋‘ ๋ฌธ์ œ๋ฅผ ๋‹ค์Œ๊ณผ ๊ฐ™์€ ๋ฐฉ๋ฒ•์œผ๋กœ ํ•ด๊ฒฐํ•˜์˜€๋‹ค. ๋จผ์ € ์˜์‚ฌ์œ„์„ฑ๊ณผ ์ดˆ์ €๊ฐ€ IMU์˜ ๊ฒฐํ•ฉ์„ ํ†ตํ•ด ์‚ฌ์ดํด ์Šฌ๋ฆฝ์„ ๊ฒ€์ถœ ๋ฐ ๋ณด์ƒํ•ด ์คŒ์œผ๋กœ์จ ์˜์‚ฌ์œ„์„ฑ ์‹œ์Šคํ…œ์— ๋‚จ์•„์žˆ๋˜ ๋ฌธ์ œ์ ์ธ ์‚ฌ์ดํด ์Šฌ๋ฆฝ ๋ฐœ์ƒ ๋ฌธ์ œ๋ฅผ ํ•ด๊ฒฐํ•˜๊ณ ์ž ํ•˜์˜€๋‹ค. ๋˜ํ•œ ์‹ค๋‚ดํ™˜๊ฒฝ์—์„œ๋Š” ์‚ฌ์ดํด ์Šฌ๋ฆฝ์˜ ๋ฐœ์ƒ๋ฅ ์ด ๋†’๊ธฐ ๋•Œ๋ฌธ์— ํ•˜ํ”„ ์‚ฌ์ดํด ๋‹จ์œ„์˜ ์Šฌ๋ฆฝ ์—ญ์‹œ ์ž์ฃผ ๋ฐœ์ƒํ•˜๊ฒŒ ๋˜๋ฏ€๋กœ ์‚ฌ์ดํด ์Šฌ๋ฆฝ ๊ฒ€์ถœ ๋ฐ ๋ณด์ƒ์„ ํ•˜ํ”„ ์‚ฌ์ดํด ๋‹จ์œ„๊นŒ์ง€ ํ•ด์คŒ์œผ๋กœ์จ ์ด๋ฅผ ํ•ด๊ฒฐํ•˜๊ณ ์ž ํ•˜์˜€๋‹ค. ์ตœ๊ทผ ์Šค๋งˆํŠธ ํฐ์˜ ๋ฐœ๋‹ฌ๋กœ ์ธํ•ด ์Šค๋งˆํŠธํฐ์„ ํ™œ์šฉํ•˜์—ฌ ์ˆ˜ํ–‰ํ•  ์ˆ˜ ์žˆ๋Š” ์ž‘์—…๋“ค์˜ ๊ธฐ์ˆ ์  ์ˆ˜์ค€๊ณผ ํ™œ์šฉ๋ฒ”์œ„๊ฐ€ ๋ชจ๋‘ ์ฆ๊ฐ€ํ•˜๊ณ  ์žˆ๋‹ค. ์ด์— ๋”ฐ๋ผ ๊ถ๊ทน์ ์œผ๋กœ๋Š” ์Šค๋งˆํŠธ ํฐ ๋‚ด์—์„œ ์ด ๋ชจ๋“  ์ž‘์—…์ด ์ˆ˜ํ–‰๋˜๋Š” ์‹ค๋‚ด ํ•ญ๋ฒ•์„ ๊ฐœ๋ฐœํ•˜๋Š” ๊ฒƒ์ด ๋ชฉํ‘œ์ด๋‹ค. ๊ทธ ๊ณผ์ •์˜ ์ผํ™˜์œผ๋กœ ์Šค๋งˆํŠธ ํฐ์— ๋‚ด์žฅ๋œ ์ดˆ์ €๊ฐ€ IMU๋ฅผ ์˜์‚ฌ์œ„์„ฑ/IMU ๊ฒฐํ•ฉ์— ์‚ฌ์šฉํ•˜์˜€๊ณ  ์ดˆ์ €๊ฐ€ IMU๋ฅผ ์‚ฌ์šฉํ•˜๊ธฐ ์œ„ํ•œ ์„ผ์„œ ๋ชจ๋ธ๋ง์„ ์ˆ˜ํ–‰ํ•˜์˜€์œผ๋ฉฐ ๋ฐ์ดํ„ฐ์— ์กด์žฌํ•˜๋Š” ์ด์ƒ ๋ฌธ์ œ ๋“ฑ์„ ์ฒ˜๋ฆฌํ•˜์˜€๋‹ค. ๊ฒฐ๊ณผ์ ์œผ๋กœ ์˜์‚ฌ์œ„์„ฑ ๋‹จ๋… ๋Œ€๋น„ ์˜์‚ฌ์œ„์„ฑ/์ดˆ์ €๊ฐ€ IMU ๊ฒฐํ•ฉํ•ญ๋ฒ•์˜ ์œ„์น˜ ์ •ํ™•๋„๋Š” 30%์ •๋„ ํ–ฅ์ƒ๋˜์—ˆ์œผ๋ฉฐ ํ•˜ํ”„ ์‚ฌ์ดํด ์Šฌ๋ฆฝ ๊ฒ€์ถœ์— ์žˆ์–ด์„œ๋Š” threshold๋ฅผ 0.5 half cycle ๋กœ ์„ค์ •ํ•˜์˜€์„ ๊ฒฝ์šฐ false alarm๊ณผ miss detection์˜ ๋ฐœ์ƒ ํ™•๋ฅ ์ด ใ€–10ใ€—^(-8) ์ˆ˜์ค€์ด์—ˆ๋‹ค. ์ด ๊ฒฐ๊ณผ๋ฅผ ํ™•์ธํ•˜๊ธฐ ์œ„ํ•ด KOBUKI`๋กœ๋ด‡๊ณผ ์Šค๋งˆํŠธ ํฐ์„ ์ด์šฉํ•˜์—ฌ ์‹ค์‹œ๊ฐ„ ํ•ญ๋ฒ•์„ ๊ตฌํ˜„ํ•˜์˜€์œผ๋ฉฐ ์‹ค์‹œ๊ฐ„์œผ๋กœ ํ•˜ํ”„ ์‚ฌ์ดํด ๋‹จ์œ„์˜ ์Šฌ๋ฆฝ๋“ค์„ ์ž„์˜๋กœ ๋ฐœ์ƒ์‹œํ‚ค๋”๋ผ๋„ ๊ฒ€์ถœ ๋ฐ ๋ณด์ƒ๋˜์–ด ํ•ญ๋ฒ•๊ณผ ์ œ์–ด๊ฐ€ ์ž˜ ์œ ์ง€๋˜๋Š” ๊ฒƒ์„ ํ™•์ธํ•˜์˜€๋‹ค.์ œ 1 ์žฅ ์„œ ๋ก  1 ์ œ 1 ์ ˆ ์—ฐ๊ตฌ ๋™๊ธฐ ๋ฐ ๋ชฉ์  1 ์ œ 2 ์ ˆ ์—ฐ๊ตฌ ๋™ํ–ฅ 2 ์ œ 3 ์ ˆ ์—ฐ๊ตฌ ๋‚ด์šฉ ๋ฐ ๋ฐฉ๋ฒ• 5 ์ œ 4 ์ ˆ ์—ฐ๊ตฌ์˜ ๊ธฐ์—ฌ๋„ 6 ์ œ 2 ์žฅ Extended Kalman Filter๋ฅผ ํ†ตํ•œ ์˜์‚ฌ์œ„์„ฑ/์ดˆ์ €๊ฐ€ IMU ๊ฒฐํ•ฉ 7 ์ œ 1 ์ ˆ ์˜์‚ฌ์œ„์„ฑ ๊ธฐ๋ฐ˜ ์‹ค๋‚ดํ•ญ๋ฒ•์‹œ์Šคํ…œ 7 1. ์˜ค์ฐจ ์š”์†Œ 8 2. CDGPS 8 ์ œ 2 ์ ˆ ์ดˆ์ €๊ฐ€ IMU 10 1. ๊ฐ€์†๋„๊ณ„ 10 2. ์ž์ด๋กœ์Šค์ฝ”ํ”„ 16 3. ์„ผ์„œ ๋ฐ์ดํ„ฐ ์ด์ƒ ํ˜„์ƒ 21 ์ œ 3 ์ ˆ ์ „์ฒด ์‹œ์Šคํ…œ ๊ตฌ์„ฑ 23 ์ œ 4 ์ ˆ Extended Kalman Filter 24 1. State 25 2. Nonlinear Equation 25 3. State Equation 26 ์ œ 5 ์ ˆ Sensor Bias Modeling ๋ฐ ๋ฐ์ดํ„ฐ ์ด์ƒํ˜„์ƒ ํ•ด๊ฒฐ 27 1. ๊ฐ€์†๋„๊ณ„ Bias Modeling 28 2. ์ž์ด๋กœ์Šค์ฝ”ํ”„ Bias Modeling 29 3. ๊ฐ€์†๋„๊ณ„ ๋ฐ์ดํ„ฐ ์ด์ƒ ๋ฌธ์ œ ํ•ด๊ฒฐ 29 4. ์ž์ด๋กœ์Šค์ฝ”ํ”„ ๋ฐ์ดํ„ฐ ์ด์ƒ ๋ฌธ์ œ ํ•ด๊ฒฐ 31 ์ œ 6 ์ ˆ ์†๋„, ํ—ค๋”ฉ Measurement 34 1. ์†๋„ Measurement 34 2. ํ—ค๋”ฉ Measurement 37 ์ œ 7 ์ ˆ Process Noise and Measurement Noise 38 1. Process Noise 38 2. Measurement Noise 39 ์ œ 3 ์žฅ ํ•˜ํ”„ ์‚ฌ์ดํด ์Šฌ๋ฆฝ ๊ฒ€์ถœ ๋ฐ ๋ณด์ƒ 41 ์ œ 1 ์ ˆ ์˜์‚ฌ์œ„์„ฑ ๋ฐ˜์†กํŒŒ๋ฅผ ์ด์šฉํ•œ ์‹ค๋‚ดํ•ญ๋ฒ•์—์„œ์˜ ํ•˜ํ”„ ์‚ฌ์ดํด ์Šฌ๋ฆฝ ๋ฐœ์ƒ 41 ์ œ 2 ์ ˆ ์‚ฌ์ดํด ์Šฌ๋ฆฝ ๊ฒ€์ถœ ์•Œ๊ณ ๋ฆฌ์ฆ˜ 43 ์ œ 3 ์ ˆ ํ•˜ํ”„ ์‚ฌ์ดํด ์Šฌ๋ฆฝ์˜ ๊ฒ€์ถœ ํ™•๋ฅ  46 ์ œ 4 ์ ˆ Monitoring Value ์ž”์—ฌ์˜ค์ฐจ ๋ถ„์„ 49 1. Carrier Phase ์ธก์ •์น˜์— ๋ฐœ์ƒํ•˜๋Š” ์˜ค์ฐจ 50 2. ๊ฒฐํ•ฉํ•ญ๋ฒ•์œผ๋กœ ์ถ”์ •ํ•œ Distance ํ•ญ์— ํฌํ•จ๋˜๋Š” ์˜ค์ฐจ 51 ์ œ 5 ์ ˆ ์‚ฌ์ดํด ์Šฌ๋ฆฝ ๋ณด์ƒ ์•Œ๊ณ ๋ฆฌ์ฆ˜ 60 ์ œ 4 ์žฅ ์‹ค์‹œ๊ฐ„ ํ•ญ๋ฒ• ๊ตฌ์„ฑ ๋ฐ ๊ฒฐ๊ณผ 62 ์ œ 1 ์ ˆ ์‹ค์‹œ๊ฐ„ ํ•ญ๋ฒ• ๊ตฌ์„ฑ 62 1. ์ „์ฒด ์žฅ๋น„ ๊ตฌ์„ฑ 62 2. ์‹œ๋ฆฌ์–ผ ํ†ต์‹  ๊ตฌ์„ฑ 63 3. ์‹ค์‹œ๊ฐ„ ํ•ญ๋ฒ• ํ”„๋กœ๊ทธ๋žจ 66 ์ œ 2 ์ ˆ ๊ฒฐ๊ณผ 68 1. ์‹ค์‹œ๊ฐ„ ํ•ญ๋ฒ• ๊ฒฐ๊ณผ 68 2. ํ•˜ํ”„ ์‚ฌ์ดํด ์Šฌ๋ฆฝ ๊ฒ€์ถœ ๋ฐ ๋ณด์ƒ ๊ฒฐ๊ณผ 70 ์ œ 5 ์žฅ ๊ฒฐ๋ก  75 ์ฐธ๊ณ  ๋ฌธํ—Œ 77Maste

    Modes dรฉgradรฉs rรฉsultant de l'utilisation multi constellation du GNSS

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    Actuellement, on constate dans le domaine de la navigation, un besoin croissant de localisation par satellites. Apres une course a l'amelioration de la precision (maintenant proche de quelques centimetres grace a des techniques de lever d'ambiguite sur des mesures de phase), la releve du nouveau defi de l'amelioration de l'integrite du GNSS (GPS, Galileo) est a present engagee. L'integrite represente le degre de confiance que l'on peut placer dans l'exactitude des informations fournies par le systeme, ainsi que la capacite a avertir l'utilisateur d'un dysfonctionnement du GNSS dans un delai raisonnable. Le concept d'integrite du GNSS multi-constellation necessite une coordination au niveau de l'architecture des futurs recepteurs combines (GPS-Galileo). Le fonctionnement d'un tel recepteur dans le cas de passage du systeme multi-constellation en mode degrade est un probleme tres important pour l'integrite de navigation. Cette these se focalise sur les problemes lies a la navigation aeronautique multiconstellation et multi-systeme GNSS. En particulier, les conditions de fourniture de solution de navigation integre sont evaluees durant la phase d'approche APV I (avec guidage vertical). En disposant du GPS existant, du systeme Galileo et d'un systeme complementaire geostationnaire (SBAS), dont les satellites emettent sur des frequences aeronautiques en bande ARNS, la question fondamentale est comment tirer tous les benefices d'un tel systeme multi-constellation pour un recepteur embarque a bord d'un avion civil. En particulier, la question du maintien du niveau de performance durant cette phase de vol APV, en termes de precision, continuite, integrite et disponibilite, lorsque l'une des composantes du systeme est degradee ou perdu, doit etre resolue. L'objectif de ce travail de these est donc d'etudier la capacite d'un recepteur combine avionique d'effectuer la tache de reconfiguration de l'algorithme de traitement apres l'apparition de pannes ou d'interferences dans une partie du systeme GNSS multiconstellation et d'emettre un signal d'alarme dans le cas ou les performances de la partie du systeme non contaminee ne sont pas suffisantes pour continuer l'operation en cours en respectant les exigences de l'aviation civile. Egalement, l'objectif de ce travail est d'etudier les methodes associees a l'execution de cette reconfiguration pour garantir l'utilisation de la partie du systeme GNSS multi-constellation non contaminee dans les meilleures conditions. Cette etude a donc un interet pour les constructeurs des futurs recepteurs avioniques multiconstellation. ABSTRACT : The International Civil Aviation Organization (ICAO) has defined the concept of Global Navigation Satellite System (GNSS), which corresponds to the set of systems allowing to perform satellite-based navigation while fulfilling ICAO requirements. The US Global Positioning Sysem (GPS) is a satellite-based navigation system which constitutes one of the components of the GNSS. Currently, this system broadcasts a civil signal, called L1 C/A, within an Aeronautical Radio Navigation Services (ARNS) band. The GPS is being modernized and will broadcast two new civil signals: L2C (not in an ARNS band) and L5 in another ARNS band. Galileo is the European counterpart of GPS. It will broadcast three signals in an ARNS band: Galileo E1 OS (Open Service) will be transmitted in the GPS L1 frequency band and Galileo E5a and E5b will be broadcasted in the same 960-1215 MHz ARNS band than that of GPS L5. GPS L5 and Galileo E1, E5a, E5b components are expected to provide operational benefits for civil aviation use. However, civil aviation requirements are very stringent and up to now, the bare systems alone cannot be used as a means of navigation. For instance, the GPS standalone does not implement sufficient integrity monitoring. Therefore, in order to ensure the levels of performance required by civil aviation in terms of accuracy, integrity, continuity of service and availability, ICAO standards define different systems/algorithms to augment the basic constellations. GPS, Galileo and the augmentation systems could be combined to comply with the ICAO requirements and complete the lack of GPS or Galileo standalone performance. In order to take benefits of new GNSS signals, and to provide the service level required by the ICAO, the architecture of future combined GNSS receivers must be standardized. The European Organization for Civil Aviation Equipment (EUROCAE) Working Group 62, which is in charge of Galileo standardization for civil aviation in Europe, proposes new combined receivers architectures, in coordination with the Radio Technical Commission for Aeronautics (RTCA). The main objective of this thesis is to contribute to the efforts made by the WG 62 by providing inputs necessary to build future receivers architecture to take benefits of GPS, Galileo and augmentation systems. In this report, we propose some key elements of the combined receivers' architecture to comply with approach phases of flight requirements. In case of perturbation preventing one of the needed GNSS components to meet a phase of flight required performance, it is necessary to be able to switch to another available component in order to try to maintain if possible the level of performance in terms of continuity, integrity, availability and accuracy. That is why future combined receivers must be capable of detecting the impact of perturbations that may lead to the loss of one GNSS component, in order to be able to initiate a switch. These perturbations are mainly atmospheric disturbances, interferences and multipath. In this thesis we focus on the particular cases of interferences and ionosphere perturbations. The interferences are among the most feared events in civil aviation use of GNSS. Detection, estimation and removal of the effect of interference on GNSS signals remain open issues and may affect pseudorange measurements accuracy, as well as integrity, continuity and availability of these measurements. In literature, many different interference detection algorithms have been proposed, at the receiver antenna level, at the front-end level. Detection within tracking loops is not widely studied to our knowledge. That is why, in this thesis, we address the problem of interference detection at the correlators outputs. The particular case of CW interferences detection on the GPS L1 C/A and Galileo E1 OS signals processing is proposed. Nominal dual frequency measurements provide a good estimation of ionospheric delay. In addition, the combination of GPS or GALILEO navigation signals processing at the receiver level is expected to provide important improvements for civil aviation. It could, potentially with augmentations, provide better accuracy and availability of ionospheric correction measurements. Indeed, GPS users will be able to combine GPS L1 and L5 frequencies, and future GALILEO E1 and E5 signals will bring their contribution. However, if affected by a Radio Frequency Interference, a receiver can lose one or more frequencies leading to the use of only one frequency to estimate the ionospheric code delay. Therefore, it is felt by the authors as an important task to investigate techniques aimed at sustaining multi-frequency performance when a multi constellation receiver installed in an aircraft is suddenly affected by radiofrequency interference, during critical phases of flight. This problem is identified for instance in [NATS, 2003]. Consequently, in this thesis, we investigate techniques to maintain dual frequency performances when a frequency is lost (L1 C/A or E1 OS for instance) after an interference occurrence

    Robust GNSS Point Positioning in the Presence of Cycle Slips and Observation Gaps

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    Among the various factors limiting accurate positioning with a Global Navigation Satellite System (GNSS) is the inherent code error level on a code observation, cycle slip occurrence on a phase observation, inadequate accuracy in the broadcast ionospheric model for single-frequency receivers; and the occurrence of observation gaps, which are short duration satellite outages (temporal loss of an observed satellite). The existing Cycle Slip Detection and Correction (CSDC) techniques are usually multi-satellite based; quite computationally intensive; and are often marred by the inherent code errors from the included code observations. Also, existing code-carrier smoothing techniques employed to mitigate code errors are limited by cycle slip occurrences on phase observations. In this research, algorithms are proposed in order to facilitate simple, efficient and real-time cycle slip detection, determination and correction, on a standalone single- or dual-frequency receiver; to enable cycle-slip-resilient code errors mitigation; and to improve the broadcast ionospheric model for single-frequency receivers. The proposed single-satellite and phase-only-derived CSDC algorithms are based on adaptive time differencing of short time series phase observables. To further provide robustness to the impact of an observation gap occurrence for an observed satellite, post-gap ionospheric delay is predicted assuming a linearly varying ionospheric delay over a short interval, which consequently enables the dual-frequency post-gap cycle slip determination and code error mitigation. The proposed CSDC algorithms showed good performance, with or without simulated cycle slips on actual data obtained with static and kinematic GNSS receivers. Over different simulated cycle slip conditions, a minimum of 97.3% correct detection and 79.8% correctly fixed cycle slips were achieved with single-frequency data; while a minimum of 99.9% correct detection and 95.1% correctly fixed cycle slips were achieved with dual-frequency data. The point positioning results obtained with the proposed methods that integrates the new code error mitigation and cycle slip detection and correction algorithms, showed significant improvement over the conventional code-carrier smoothing technique (i.e. a standalone Hatch filter, without inclusion of any cycle slip fixing method). Under different simulated cycle slip scenarios, the new methods achieved 25-42% single-frequency positioning accuracy improvement over the standalone Hatch filter, and achieved 18-55% dual-frequency positioning accuracy improvement over the standalone Hatch filter

    Low-cost GPS/GLONASS Precise Positioning in Constrained Environment

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    GNSS and particularly GPS and GLONASS systems are currently used in some geodetic applications to obtain a centimeter-level precise position. Such a level of accuracy is obtained by performing complex processing on expensive high-end receivers and antennas, and by using precise corrections. Moreover, these applications are typically performed in clear-sky environments and cannot be applied in constrained environments. The constant improvement in GNSS availability and accuracy should allow the development of various applications in which precise positioning is required, such as automatic people transportation or advanced driver assistance systems. Moreover, the recent release on the market of low-cost receivers capable of delivering raw data from multiple constellations gives a glimpse of the potential improvement and the collapse in prices of precise positioning techniques. However, one of the challenge of road user precise positioning techniques is their availability in all types of environments potentially encountered, notably constrained environments (dense tree canopy, urban environmentsโ€ฆ). This difficulty is amplified by the use of low-cost receivers and antennas, which potentially deliver lower quality measurements. In this context the goal of this PhD study was to develop a precise positioning algorithm based on code, Doppler and carrier phase measurements from a low-cost receiver, potentially in a constrained environment. In particular, a precise positioning software based on RTK algorithm is described in this PhD study. It is demonstrated that GPS and GLONASS measurements from a low-cost receivers can be used to estimate carrier phase ambiguities as integers. The lower quality of measurements is handled by appropriately weighting and masking measurements, as well as performing an efficient outlier exclusion technique. Finally, an innovative cycle slip resolution technique is proposed. Two measurements campaigns were performed to assess the performance of the proposed algorithm. A horizontal position error 95th percentile of less than 70 centimeters is reached in a beltway environment in both campaigns, whereas a 95th percentile of less than 3.5 meters is reached in urban environment. Therefore, this study demonstrates the possibility of precisely estimating the position of a road user using low-cost hardware

    Geodetic Sciences

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    Space geodetic techniques, e.g., global navigation satellite systems (GNSS), Very Long Baseline Interferometry (VLBI), satellite gravimetry and altimetry, and GNSS Reflectometry & Radio Occultation, are capable of measuring small changes of the Earth๏ฟฝs shape, rotation, and gravity field, as well as mass changes in the Earth system with an unprecedented accuracy. This book is devoted to presenting recent results and development in space geodetic techniques and sciences, including GNSS, VLBI, gravimetry, geoid, geodetic atmosphere, geodetic geophysics and geodetic mass transport associated with the ocean, hydrology, cryosphere and solid-Earth. This book provides a good reference for geodetic techniques, engineers, scientists as well as user community
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