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How multipath error influences modernized GNSS ambiguity resolution in urban areas
Nobuaki KUBO,Akio YASUDA 한국항해항만학회 2006 한국항해항만학회 학술대회논문집 Vol.2 No.-
Commercial uses of GPS have been growing rapidly with applications for aircraft, ship, and land vehicle navigation as well as for surveying and time keeping. The next generation GPS and Japanese QZS (Quasi Zenith Satellite) will provide three different civil signals. Galileo will also provide several types of civil signals. The availability of the third civil frequency has obvious advantages to instantaneous carrier phase accuracy and ambiguity resolution for centimeter level measurements. This paper discusses the effects of additional new civil signals for the high accuracy positioning in urban areas based on simulation using practical raw data. As for constellation, only GPS and GPS+QZS are considered. For positioning, a short distance baseline is assumed in order to disregard atmosphere effects. In this simulation, mask angle and signal conditions were fixed and ambiguity success rates were compared between different triple frequency combination scenarios. The coefficient of reflection was set randomly from 0.05 to 0.5 and the multipath delay was also set randomly from 5-100 m. Visible satellites and signal strength were determined by raw data collected in Tokyo by car. These simulation results have confirmed that the availability of high accuracy positioning will increase in all scenarios if we use GPS+QZS with triple frequencies.
Experiments for utilizing GNSS in a shore area Sensor Network
Harumasa Hojo,Akio Yasuda,Chunming Fan,Masashi Yoshida,Yoshikazu Koike,Masateru Minami 한국항해항만학회 2006 한국항해항만학회 학술대회논문집 Vol.2 No.-
Modernized GNSS such as new GPS signals updated GLONASS and coming Galileo promises higher quality and higher reliability for users. Powerful technologies such as Internet, ubiquitous network technology and sensor network has been used to promote a safe and more secure lifestyle. This report describes experimental trials to combine these technologies namely GPS and Sensor Network into a high-performance system. GPS is used to enlarge the cation range, resolving the service area limitations, as a wider service area s required at shore areas compared to urban area. GPS position datum is also used as primary network routing information to get practical Sensor Network. Another application s e under water Sensor Network. Accurate GPS position and time are used to establish stable and high reliability underwater acoustic sensor Network. This paper describes the background of the project "Harbor area Marine Ubiquitous Sensor Network", preliminary consideration and testing. Radio and acoustic communication is the main focus of this preliminary experiment.
Airborne GPS Reflectometry from Low Altitude Aircraft
Takuji Ebinuma,Yasuda Akio,Dinesh Manandhar 제어로봇시스템학회 2009 제어로봇시스템학회 국제학술대회 논문집 Vol.2009 No.8
This work is intended to develop a software-defined Global Positioning System (GPS) receiver specifically designed to process reflected GPS signal off the ground or the ocean surface for purpose of remote sensing. A set of airborne campaign was conducted to evaluate the performance of the prototype GPS reflectometry receiver. The reflected signal was tracked in open-loop manner using the so called delay mapping receiver. The result shows that theprototype receiver was capable of providing altimetric measurements with a precision level of the order of few meterswith an unknown system bias which should be estimated.
Safety Confirmation of Ship's Crew Using Cell-phone with GPS Receiver and Wireless LAN
Chie Umeno,Hiromune Namie,Osamu Susuki,Akio Yasuda 한국항해항만학회 2006 한국항해항만학회 학술대회논문집 Vol.2 No.-
Ships and their cargos have been managed safely by positioning report system. However, little attention has been paid to safety of crew's works with danger. The attempt that used PHS inboard was before by the present authors. However, the functions were just voice call and mail exchange. The data acquisition from the terminal by proper control was not possible. Thus the position of the terminal was not available. As for the cell phone of next generation, GPS receiver and wireless LAN are installed by manufacturers. Therefore, we propose a system which uses a cell-phone with GPS receiver on a ship in order to promote the safety of ship's crew. We checked the availability of cell-phone GPS receiver at thirty different points inboard. The positioning was not possible in the areas further than 4m from the window. Then, we proposed the system which follows the positions of the crews and confirms their safety inboard by using the VoIP (Voice over Internet Protocol) function by wireless LAN.
Shun-Ichiro Kondo,Nobuaki Kubo,Akio Yasuda 한국항해항만학회 2006 한국항해항만학회 학술대회논문집 Vol.2 No.-
Ionospheric scintillation induces a rapid change in the amplitude and phase of radio wave signals. This is due to irregularities of electron density in the F-region of the ionosphere. It reduces the accuracy of both pseudorange and carrier phase measurements in GPS/satellite based Augmentation system (SBAS) receivers, and can cause loss of lock on the satellite signal. Scintillation is not as strong at mid-latitude regions such that positioning is not affected as much. Serve effects of scintillation occur mainly in a band approximately 20 degrees on either side of the magnetic equator and sometimes in the polar and auroral regions. Most scintillation occurs for a few hours after sunset during the peak years of the solar cycle. This paper focuses on estimation of the effects of ionospheric scintillation on GPS and SBAS signals using a software receiver. Software receivers have the advantage of flexibility over conventional receivers in examining performance. PC based receivers are especially effective in studying errors such as multipath and ionospheric scintillation. This is because it is possible to analyze IF signal data stored in host PC by the various processing algorithms. A LI C/A software GPS receivers was developed consisting of a RF front-end module and a signal processing program on the PC. The RF program written in MATLAB implements signal acquisition, tracking, and pseudorange measurements. The receiver achieves standalone positioning with accuracy between 5 and 10 meters in 2drms. Typical phase locked loop (PLL) designs of GPS/SBAS receivers enable them to handle moderate amounts of scintillation. So the effects of ionospheric scintillation was estimated on the performance of GPS LI C/A and SBAS receivers in terms of degradation of PLL accuracy considering the effect of various noise sources such as thermal noise jitter, ionospheric phase jitter and dynamic stress error.
Evaluation of Ambiguity Estimator between Reference Stations
Yasuto Gomi,Reiji Tominaga,Nobuaki Kubo,Akio Yasuda 한국항해항만학회 2006 한국항해항만학회 학술대회논문집 Vol.2 No.-
In order to apply the network adjustment, the correct ambiguities between each of reference stations must be calculated. This paper focused on the comparison of ambiguity resolution between the reference stations. Three hours test data with different baseline length from 20 km to 60 km have been analyzed. The results show that the time-to-fix between 20 km and 40 km is typically under 1 minute. However, over 60km baseline, the time-to-fix performance degrades.
The Benefit of Ambiguity Resolution Using Triple Frequency
Reiji Tominaga,Yasuto Gomi,Yun Zhang,Nobuaki Kubo,Akio Yasuda 한국항해항만학회 2006 한국항해항만학회 학술대회논문집 Vol.2 No.-
Modernized GPS will have three frequencies modulated with three signals, which will be accessible to all users in the near future. This new frequency provides an opportunity to resolve the double differenced (DD) integer ambiguity very fast and with almost no baseline constraints. In order to study the performance of triple frequency system for Ambiguity Resolution (AR) over the medium baseline under different ionospheric levels, the Klobuchar Model was implemented and used in our triple simulation to generate the ionospheric delay. Furthermore, the White-Gaussian noise applying to distance-dependent parameters was added to the DD ionospheric delay. For medium baseline (defined as here 20 to 40kms), success rates of AR has been pretty improved. In this paper, the medium baseline AR strategies that take advantage of carrier phase measurement on the third frequency will be discussed.