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The new GPS L5 signal, is a part of the U.S. efforts to modernize its global positioning system (GPS). It was designed to support safety of life applications such as civil aviation navigation. Its structure designed to provide higher performance in terms of measurement accuracy. Till now, the GPS system cannot transmit L5 from all satellites. So, in this paper a GPS simulator software in MATLAB environment was implemented to simulate RINEX observations files with the three frequencies. MATLAB: GPSDP (GPS Differential Processing) program was used to process static and kinematic data from all three frequencies . RINEX files for both base and rover stations had been generated for different baselines lengths 5, 50 and 100 km approximately in different day times. These data are used to study the impact of the third frequency on rate of resolving integer ambiguities and the time needed to fix the integer ambiguities correctly. Also, the positioning accuracy after adding the third frequency to dual frequencies data. All parameters are studied under variation of ionosphere intensities. The results of experiments have been illustrated and they show efficiency of using the third frequency over dual frequencies.

The Quasi-Zenith Satellite System(QZSS) is the Japanese satellite navigation system, which designs to increase the GPS system's visibility in the urban areas. The first satellite(Michibiki) was launched in 2010 and started to broadcast navigation signals. Therefore, the purpose of the research is to analyze the performance of GPS and QZSS based on the advantage of the integrated GNSS. Especially, the study has been processed in terms of improving satellite navigation parameters around Korean Peninsula. To do this, there have been the comprehensive analysis of the QZSS characteristics, the experimental test, and its statistical analysis for realizing advantage of GPS and QZSS. Through these systemic steps, it was recognized that the integrated GPS and QZSS has more reliable than GPS in case of not only limited visibility but also ordinary positioning. Additionally, the integrated GPS and QZSS would be very useful to improve the various navigation parameters around the peninsula.

The paper describes determination of GPS receiver position using Bancroft algorithm. The position is determined by obtaining pseudo ranges from seven different GPS satellites. The measured ranges do not represent the true ranges as the signal coming from a GPS satellite will be affected by various errors like Ephemeris error; Propagation error in the form of Ionospheric and Tropospheric delays; Satellite and Receiver clock biases with respect to GPS Time (GPST); Multipath error etc. Most of these errors can be estimated accurately and can be accounted for. In this paper some standard mitigation techniques have been applied for the estimation of GPS errors and user position is then determined using Bancroft algorithm technique after making appropriate corrections. GPS data of Chitrakut station available in RINEX (Receiver Independent Exchange) format have been used for this purpose u j u j u j j ct z z y y x x 2 2 2

The next few years promises drastic improvements to global navigation satellite systems. USA is modernizing GPS, Russia is GLONASS, Europe is moving ahead with its own Galileo System, and China is expanding its BeiDou system from a regional navigation system to a full constellation global navigation satellite system known as BeiDou-2/Compass. Chinese BeiDou satellite navigation system constellation currently consists of twenty-six BeiDou satellites and can provide services of navigation and positioning in the Asia-Pacific Region. In this paper, we calculate the high frequency data of GPS and BeiDou by using the broadcast ephemeris, and the results are applied to the real-time positioning of the float platform in the experiment of Air-Gun in reservoir. We use the data to analyze the quality by multipath effect, signal noise ratio, positioning accuracy and so on. The results show that the accuracy of the BeiDou is slightly lower than that of GPS. The accuracy of GPS in horizontal direction is about 5 mm and that of vertical direction is about 12 mm, and the accuracy of BeiDou in horizontal direction is about 5.5 mm and that of vertical direction is about 16 mm.

Using GPS alone may not give the desired positioning accuracy. Some applications require high accuracy, such as when an aircraft is landing. This chapter describes some ways of using additional information, that is, augmenting GPS, so as to produce a better result. One way is to have a receiver that uses signals from two GNSSs—such as GPS and GLONASS. There are potential problems with integrating two GNSSs though, as the systems have different characteristics. Another approach is to supplement GPS with a Satellite-Based Augmentation System, where geostationary satellite(s) are used to supply the additional information. Several other approaches exist, such as Network RTK and Assisted GNSS.

The Global Positioning System (GPS) has been in use for providing positioning, navigation and timing (PNT) services in many parts of the world. There are several errors that affect the positional accuracy of GPS. Prominent among them are ephemeris errors, satellite and receiver clock errors, multipath errors, signal propagation errors such as ionospheric delay, tropospheric delay, and instrumental biases of the satellite and receiver. In this paper, prominent estimation techniques to characterize various GPS measurement errors are reviewed. The GPS data in the Receiver INdependent EXchange (RINEX) format obtained from a Dual frequency GPS receiver is used in this analysis. Among all the errors, ionospheric delay is found to be the most dominant. However, these delay measurements are affected by the satellite and receiver instrumental biases. The instrumental biases exist as the signals at the two GPS frequencies experience different delays inside the satellite and receiver hardware. For estimation of the instrumental biases Extended Kalman filter(EKF) technique is adopted. The user equivalent range error (UERE) obtained due to all the error sources is of the order of few metres. After accounting for various errors, the estimation accuracy is significantly improved.The positional accuracy of the GPS Aided GEO Augmented Navigation (GAGAN) system is basically dependent on ranging errors and the satellite constellation geometry(1). The lineof-sight ionospheric measurements derived from the Global Positioning System (GPS) observables are corrupted by the instrumental biases present in both the GPS satellites and the receivers. The instrumental bias and Total Electron Content (TEC) results (Hyderabad GAGAN station (78.47°E, 17.45°N)) obtained using theExtended Kalman filter technique are presented in this paper. In this work the main focus is towards development of an improved error free approach for aircraft navigation. The existing navigation solutions are based on iterative algorithms and require an initial estimate of the receiver position for computing the navigation solution which is not possible in all conditions. Accurate, reliable and cost effective navigation solution algorithms that suit the Indian geographic area and area of application are proposed in this work. A non-iterative point solution approach algorithm computes the navigation solution based on the available satellite positions and pseudorange measurements(3). The improvement in GPS system has given a feasibility of automated operation of satellite based augmenting system in aircraft navigation can augment GAGAN and improves the positional accuracy of the user. In this paper a communication approach , high, accurate processing using EKF scheme is proposed for GPS aided geo augmented navigation (GAGAN) application. The effectiveness of the proposed approach for higher performance is evaluated under variable conditions.

The next few years promises drastic improvements to global navigation satellite systems. The USA is modernizing GPS, Russia is GLONASS, Europe is moving ahead with its own Galileo System, and China is expanding its BeiDou-1 system from a regional navigation system to a full constellation global navigation satellite system known as BeiDou-2/Compass. Chinese BeiDou satellite navigation system constellation currently consists of twenty-three BeiDou satellites and can provide services of navigation and positioning in the Asia-Pacific Region. This paper focuses on calculating the results of differential positioning with different ephemeris, combining dynamic GPS and BeiDou data of air-gun in reservoir. In this experiment, the high-frequency GPS and BeiDou data is real-time calculated by broadcast ephemeris, and the result is used for real-time positioning of the air-gun floating platform. Then we calculate the GPS data of the experiment by precise ephemeris, and the accuracy of broadcast ephemeris of GPS is verified by comparison. Finally, calculate the high frequency data of GPS and BeiDou with precise ephemeris in order to verify the accuracy of BeiDou positioning. The experimental results show that the accuracy of GPS and BeiDou navigation system are basically the same and the data of GPS and BeiDou navigation system calculated by broadcast ephemeris can record the displacement of the floating platform accurately.

This paper proposes to use a correlator-level global positioning system (GPS) line-of-sight/multipath/non-line-of-sight (LOS/MP/NLOS) signal reception classifier to improve positioning performance in an urban environment. Conventional LOS/MP/NLOS classifiers, referred to as national marine electronics association (NMEA)-level and receiver independent exchange format (RINEX)-level classifiers, are usually performed using attributes extracted from basic observables or measurements such as received signal strength, satellite elevation angle, code pseudorange, etc. The NMEA/RINEX-level classification rate is limited because the complex signal propagation in urban environment is not fully manifested in these end attributes. In this paper, LOS/MP/NLOS features were extracted at the baseband signal processing stage. Multicorrelator is implemented in a GPS software-defined receiver (SDR) and exploited to generate features from the autocorrelation function (ACF). A robust LOS/MP/NLOS classifier using a supervised machine learning algorithm, support vector machine (SVM), is then trained. It is also proposed that the Skymask and code pseudorange double difference observable are used to label the real signal type. Raw GPS intermediate frequency data were collected in urban areas in Hong Kong and were postprocessed using a self-developed SDR, which can easily output correlator-level LOS/MP/NLOS features. The SDR measurements were saved in the file with the format of NMEA and RINEX. A fair comparison among NMEA-, RINEX-, and correlator-level classifiers was then carried out on a common ground. Results show that the correlator-level classifier improves the metric of F1 score by about 25% over the conventional NMEA- and RINEX-level classifiers for testing data collected at different places to that of training data. In addition to this finding, correlator-level classifier is found to be more feasible in practical applications due to its less dependency on surrounding scenarios compared with the NMEA/RINEX-level classifiers.

Since GPS system became available for common use, a it has been applied in many areas, including aviation. The development of portable GPS receivers provided immeasurable aid in air navigation. The paper presents EGNOS system that ensures the possibility of using GPS system for approach procedure. The article addresses the following issues: the history of creation and development of GPS, principle of system operation, accuracy in relation for GPS system, comparison with conventional radio navigation ILS system and potential benefits from implementing EGNOS.

The Global Navigation Satellite System (GNSS) like US Global Positioning System (GPS) and EU Galileo are based on providing precise time and frequency synchronized ranging signals. Because of the exploitation of very precise timing signals these GNSS are used to provide both navigation and time distribution services. Moreover, because the positioning accuracy will improve as more satellites become available, we should expect that a combination of Galileo and GPS will provide better performance than those of both systems separately. However, Galileo will not use the same time reference as GPS and thus, a time difference arises - the GPS-Galileo Time Offset (GGTO). The navigation solution calculated by receivers using signals from both navigation systems will consequently contain a supplementary error if the GGTO is not accounted for. In this paper, we compared GPS Time (GPST) with Galileo Sytem Time (GST) and analyzed the effects of GGTO on positioning accuracy by simulation test. And then we also analyzed the characteristics of two representative GGTO correction methods such as the navigation message based method at system level and the estimation method at user level and propose the conceptual design of the novel correction method being capable of preventing previous method`s problems.

The Chinese BeiDou navigation satellite system (BDS) aims to provide global positioning service by 2020. The combined use of BDS and Global Positioning System (GPS) is proposed to provide navigation service with more stringent requirements. Actual satellite data, signals and measurements were collected for more than one month to analyze the positioning service qualities from both BDS and GPS. In addition to the conversions of coordinate and timing system, five data quality analysis (DQA) methods, three signal quality analysis (SQA) methods, and four measurement quality analysis (MQA) methods are proposed in this paper to improve the integrated positioning performance of BDS and GPS. As shown in the experiment results, issues related to BDS and GPS are resolved by the above proposed quality analysis methods. Thus, the anomalies in satellite data, signals and measurements can be detected by following the suggested resolutions to enhance the positioning performance of the combined use of BDS and GPS in the Asia Pacific region.

Global navigation satellite systems (GNSSs) have been experiencing a rapid growth in recent years with the inclusion of Galileo and BeiDou navigation satellite systems. The existing GPS and GLONASS systems are also being modernized to better serve the current challenging applications under harsh signal conditions. Therefore, the research and development of GNSS receivers have been experiencing a new upsurge in view of multi-GNSS constellations. In this article, a multi-GNSS receiver design is presented in various processing stages for three different GNSS systems, namely, GPS, Galileo, and the Chinese BeiDou navigation satellite system (BDS). The developed multi-GNSS software-defined receiver performance is analyzed with real static data and utilizing a hardware signal simulator. The performance analysis is carried out for each individual system, and it is then compared against each possible multi-GNSS combination. The true multi-GNSS benefits are also highlighted via an urban scenario test carried out with the hardware signal simulator. In open sky tests, the horizontal 50 % error is approximately 3 m for GPS only, 1.8 to 2.8 m for combinations of any two systems, and 1.4 m when using GPS, Galileo, and BDS satellites. The vertical 50 % error reduces from 4.6 to 3.9 when using all the three systems compared to GPS only. In severe urban canyons, the position error for GPS only can be more than ten times larger, and the solution availability can be less than half of the availability for a multi-GNSS solution.

The integrity monitoring of anomalous GPS signal have been researched because of the degradation of GPS satellite performance. It is known that anomalous GPS signal can occur by failure of GPS satellite, sudden increase of ionosphere delay error, SA, wrong modeling for navigation parameters from control segment, and an electromagnetic wave interference, etc. In case of GPS anomaly by satellites can arise from carrier frequency, code and navigation message. In this paper, the scenarios with navigation message errors were made by using GPS simulator, and the influences of GPS navigation message error to receiver were analysed. The anomalies of preamble, bits related TOW count message, subframe ID in HOW, bits related satellite healthy, and the other navigation message errors were described and simulated. Also, the number of satellites, DOP and pseudorange are analyzed to know how the anomalous signal can affect on GPS receiver.

The users who use a combined GPS/Galileo receiver will benefit from an improved availability of the combined system and a reduced dependence on one particular positioning system. However, these users must solve the problem of an offset between the time scales of GPS and Galileo (GGTO). GGTO must be analyzed for not only a navigation system but also a timing system requesting precise time service. This paper analyzes the interoperability problem in a combined GPS/Galileo timing receiver and estimates the timing performance under various assumptions. The GPS real measurements were collected by using the commercial timing receiver from Ashtech Ltd. and the Galileo measurements were generated by a simulation software. A suitable test scenario set-up and the performance in a point of timing stability was evaluated.

Navigation users will significantly benefit from the combined use of GPS and GLONASS due to the improved reliability, availability and accuracy especially in an environment with limited satellite visibility, such as in urban or mountainous areas. But in such situations the visible satellite number is often still insufficient to obtain a position solution even if both GPS and GLONASS measurements are used. This is partly because at least five visible satellites are required to determine a position due to an offset between the timescales of GPS and GLONASS to be solved. In this paper, an algorithm has been proposed to obtain a position solution with only four visible GPS/GLONASS satellites. In addition to the data from IGS stations, an experiment was also conducted to assess the proposed algorithm. The results indicate that using the proposed algorithm with only four GPS/GLONASS satellites a position solution could be obtained at the cost of a slight accuracy loss.

Today Global Navigation Satellite Systems (GNSS) are widely used for determining position. Within the city environment, however, in which there are many tall buildings, GNSS signals are frequently interrupted, making it difficult for users to obtain information on their exact position. This paper analyzed the availability and positioning performance of a GPS augmented system within the Seoul urban area using the Japanese QZSS (Quasi-Zenith Satellite System) and a geostationary satellite. A 3-dimensional reproduction of Seoul that was based on the 3D GIS (Geographic Information System) Digital Map and a satellite tracking algorithm using Ray-Triangle Intersection algorithm were discussed. A satellite tracking algorithm was verified through filed testing and the QZSS orbit simulator was realized using Keplerian parameter. DOP (Dilution of Precision) and availability in the urban area of Seoul were analyzed using a GPS/QZSS/geostationary satellite separately and simultaneously.

A GNSS(Global Navigation Satellite System) using GPS provides us with very useful information concerning the positioning of users in many sectors such as transportation, social services, the justice system and customs services, public works, search and rescue systems and leisure. A GNSS using the Galileo satellite is due to work in 2008 and expected to be used in various fields such as aviation, marine transportation, land surveying, resources development precise agriculture, telemetics, and so on. In this paper, we discuss the implementation and testing of a combined GPS/Galileo receiver which we named KSTAR V1.0. Each tracking module of GPS/Galileo dual mode correlator has the five track arms which consist of Very Early code, Early code, Prompt code, late code, and Very late code. Each of 24 tracking modules can be assigned to GPS and/or Galileo signal by changing mode selection register. The basic correlator integration dump period is set to 1ms for GPS C/A code and fast Galileo signal tracking. The performance of the developed combined GPS/Galileo receiver was tested and evaluated using the IF (Intermediated Frequency)-level GPS/Galileo signal generator.

In many monitoring applications, such as tall buildings, bridges and volcanoes, GPS offers significant advantages over other measurement techniques. GPS allows a high rate of measurement and long distances between the control and monitoring points and does not require line of sight to the control points. The traditional dual-frequency GPS receivers used in surveying are high accuracy but also relatively high cost per monitored point and therefore often prohibitive for the deployment of a GPS monitoring network. Until recently, cost effective L1 sensors and software have not been able to provide the necessary level of accuracy and reliability. A new solution from Leica Geosystems provides real time and post processed RTK positioning with L1 only GPS receivers for monitoring applications. The solution is built on Leica's RTK positioning algorithms, which have proven world-class performance in the surveying industry. The positioning algorithm used in the Leica GX1230 RTK GPS receivers has been implemented in the GPS Spider reference station software and tuned for monitoring applications, giving GPS Spider the capability to compute real time ambiguity fixed solutions for single and dual frequency GPS in addition to its powerful site configuration and data management tools. A direct link has been made between GPS Spider and Leica GeoMoS, Leica's geodetic monitoring software, so that users can combine GPS with the sophisticated terrestrial measurement capabilities of Leica’s robotic total stations and utilize GeoMoS’s flexible messaging and data analysis capabilities. In addition the RINEX data logged by GPS Spider may be automatically post processed for users with the highest accuracy and reliability requirements. This paper presents results from the system, including using a new ambiguity resolution technique, called quasi-static initialisation, designed for single frequency monitoring. Results from L1 processing are compared to a dual frequency solution in terms of accuracy and reliability. Data was collected with a range of baseline lengths up to 20km in medium multipath environments, typical of many monitoring applications. The L1 system is shown to have remarkable accuracy and reliability, especially in terms of price versus performance.

The use of GPS receiver at outer space becomes common in low earth orbit. Recently most of satellites use GPS receiver as navigation solution for finding satellite position. However, the accuracy of navigation solution acquiring directly from GPS receiver is not enough in satellite application such as map generation. Post-processing concepts such as Precise Orbit Determination (POD) are recently applied to satellite data processing to improve satellite position accuracy. The POD uses raw measurement data instead of navigation solution of GPS receiver. The performance of raw measurement data depends on raw measurement data accuracy and tracking loop algorithm of GPS receiver. In this paper, a method for evaluating performance of raw measurement data is suggested. Test environment and procedure of the low earth orbit satellite acquiring for navigation solution of GPS receiver and navigation solution of POD are described. In addition, accuracy on navigation solution of GPS receiver, raw measurement data, and navigation solution of POD are analyzed. The proposed method can be applicable to general low earth orbit satellite.

Recently we proposed an acquisition process for a maximum-likelihood GPS receiver that considers the joint processing of all GPS satellite waveforms. The resulting estimator was shown to provide an elegant solution to the near–far problem and to perform better than the suboptimal sliding-correlator estimator. However, the proposed acquisition model included only the code search, which estimates just the time of arrival (TOA) between a GPS satellite and a maximum-likelihood GPS receiver. In this paper we enhance the acquisition process by including the estimation of Doppler along with the estimation of the TOA, which results in a two-dimensional Doppler and code search. A maximum-likelihood GPS receiver would require only one front-end hardware section for processing all GPS signals in view, thus simplifying the entire architecture of a GPS receiver. An assessment based on theoretical performance and simulation results indicates that a maximum-likelihood GPS receiver can achieve an order-of-magnitude performance improvement relative to a sliding-correlator GPS receiver. Simulation data will be validated in the near future using GPS acquisition data from the Novatel ProPack AG-G2+DB9-RT2, and the results of this work will be presented in a future publication.

There are a number of online Global Positioning System (GPS) processing services that provide GPS processing results to the user free of charge and with unlimited access. These services provide solutions for a user-submitted Receiver Independent Exchange Format (RINEX) file based on differential methods using reference stations or precise point positioning using precise GPS orbit and clock data. Different data sets varying in time and location were submitted to the online services and their results compared. Although the quality of results depends on many factors, in most cases the users can expect reliable online processing results for a 10-h data set made by a geodetic dual frequency receiver anywhere in the world.

The current global positioning system (GPS) provides limited availability and capability for a country like Japan where mountainous terrain and urban canyons do not allow a clear skyline to the horizon. At present, the Japanese Quasi-Zenith Satellite System (QZSS) is under investigation through a cooperative effort between the government and the private sector. QZSS is considered a multi-function satellite system, as it is able to provide communication, broadcasting, and positioning services for mobile users in a specified region with a high elevation angle. The additional GPS compatible signals from QZSS can remarkably improve the availability, accuracy, and capability of GPS positioning. This work focuses on the performance of GPS augmentation using the proposed QZSS. The QZSS satellite constellation and signal structure are briefly reviewed. Positioning with pseudo-range and carrier phase are discussed. The performance of GPS augmentation using QZSS in the Asian-Pacific and Australian area is studied using software simulations. The results are presented using the number of visible satellites as a measure of availability, GDOP as a measure of accuracy, and ambiguity success rate as a measure of capability of carrier-phase-based positioning with spatial and temporal variations. The results show that the QZSS will improve not only the availability and accuracy of GPS positioning, but will also enhance the capability of the GPS carrier-phase-based positioning in Japan and neighboring regions.

With the European Commission (EC) and European Space Agency's (ESA) plans to develop a new satellite navigation system, Galileo and the modernisation of GPS well underway the integrity of such systems is as much, if not more, of a concern as ever. Receiver Autonomous Integrity Monitoring (RAIM) refers to the integrity monitoring of the GPS/Galileo navigation signals autonomously performed by the receiver independent of any external reference systems, apart from the navigation signals themselves. Quality measures need to be used to evaluate the RAIM performance at different locations and under various navigation modes, such as GPS only and GPS/Galileo integration, etc. The quality measures should include both the reliability and localizability measures. Reliability is used to assess the capability of GPS/Galileo receivers to detect the outliers while localizability is used to determine the capability of GPS/Galileo receivers to correctly identify the detected outlier from the measurements processed.Within this paper, the fundamental equations required for effective outlier detection and identification algorithms are described together with the measures of reliability and localizability. Detailed simulations and analyses have been performed to assess the performances of GPS only and integrated GPS/Galileo navigation solutions with respect to reliability and localizability. Simulation results show that, in comparison with the GPS-only solution, the localizability of the integrated GPS/Galileo solution can be improved by up to 270%. The results also indicate an expectation of a considerable increase in the sensitivity to outliers and accuracy of their estimation with the augmentation of the Galileo system with the existing GPS system.

Global navigation satellite systems (GNSS) is the collective term for those navigation systems that provide the user with a three-dimensional positioning solution by passive ranging using radio signals transmitted by satellites. The most well known is the Navigation by Satellite Ranging and Timing (NAVSTAR) Global Positioning System (GPS). It is the most advanced but still not free from erroneous positioning and needs better accuracy. Now European GALILEO is under development, which is interoperable with GPS. In this paper performance of GPS and GALILEO alone and combined GPS-GALILEO system has been analyzed. Simulation has also done using duel and triple frequency. This paper has also presented which system and combination gives better precision and reliability. Also a time analysis of getting highest availability is studied. Results show that the improvement of the combined system is as high as 50% as present GPS alone system.

The International Atomic Time scale (TAI) is computed by the Bureau International des Poids et Mesures (BIPM) from a set of atomic clocks distributed in about 40 time laboratories around the world. The time transfer between these remote clocks is mostly performed by the so-called GPS common view method: The clocks are connected to a GPS time receiver whose internal software computes the offsets between the remote clocks and GPS time. These data are collected in a standard formal called CCTF. In the present study we develop both the procedure and the software tool that allows us to generate the CCTF files needed for time transfer to TAI, using RINEX files produced by geodetic receivers driven by an external frequency. The CCTF files are then generated from the RINEX observation files. The software is freely available at ftp://omaftp.oma.be/dist/astro/time/RINEX_CCTF. Applied to IGS (International GPS Service) receivers, this procedure will provide a direct link between TAI and the IGS clock combination. We demonstrate here the procedure using the RINEX files from the Ashtech Metronome (ZXII-T) GPS receiver, to which we apply the conventional analysis to compute the CCTF data. We compared these results with the CCTF files produced by a time receiver R100-30T from 3S-Navigation. We also used this comparison with the results of a calibrated time receiver to determine the hardware delay of the geodetic receiver. © 2001 John Wiley & Sons, Inc.

A set of Python scripting language library modules aimed at automation and more flexible customizing of GPS data processing using Bernese software v. 4.x is described. The motivation of the development of this package is explained. A brief introduction to the Python scripting language and its application to the high level control of numerical data processing is given. A synopsis of the particular modules including those which facilitate manipulating with RINEX files, GPS dates, etc., together with those which encapsulate the Bernese functionality is presented. The strategy of GPS data preprocessing, called “optimal baseline selection loop” is described.

Hughes Aircraft is currently developing under contract with the Federal Aviation Administration (FAA) a GPS-based navigation system that is intended to become the primary navigational aid for commercial aviation during all phases of flight—from enroute through Category I precision approach. This innovative system, named the Wide-Area Augmentation System (WAAS), will make use of a network of reference stations distributed throughout the U.S. National Airspace System. These reference stations will collect GPS measurements and send them to master stations. The master stations will process the data to provide correctional information for each GPS satellite. This information will include as separate components the GPS ephemeris errors, satellite clock bias and ionospheric estimation data. The corrections will be sent to the users by means of a Geosynchronous Earth Orbit (GEO) satellite using a specific signal and data format. WAAS is first expected to provide supplemental radio navigation, and eventually to become the primary system of navigation. The system will add the following features to the current GPS system: a GEO ranging function that will improve availability and reliability; differential GPS corrections that will improve accuracy; and integrity monitoring that will provide and enhance safety. To meet the requirements associated with a primary navigation system, WAAS should be able to provide fault-free position fix with a time availability of 0.999 for Category I approaches, and 0.99999 for domestic enroute, terminal and nonprecision approach phases of flight. This paper presents the improvements that this augmentation system offers to stand-alone GPS in order to become the primary navigational system in the U.S. The paper also covers the features that make this wide-area system a naturally expandable system worldwide that will allow the integration of future local-area differential systems across the world.

In Current Scenario GPS is very popular device among people for tracking and navigation purpose but GPS data can be used for several type of applications. This GPS data can be further used for analysis the trip, elevation profile etc. There are so many GPS data formats. Different GPS receivers support different formats. There are advantages and disadvantages of each GPS format. GPS provides many types information in various format like binary, rinex etc. NMEA is one of them. In this work we develop a NMEA interpreter for logging GPS data which contains several types of information like Latitude, longitude, Time, Speed, Elevation, PDOP etc. we develop this project in VB.Net.

The paper presents analysis for using China based Beidou as satellite navigation system in Pakistan's naval vessels as an alternative or additional aid to US based GPS, which is currently most widely used system. A full scale Beidou will have lower dilution of precision implying better coverage in Arabian Sea as compared to GPS. The paper also compares Beidou open service signal B1 with conventional GPS signal L1. B1 has better performance in terms of multipath error and cross correlation noise. Lastly, design considerations for receiving B1 signal on L1 receiver are addressed in the paper in terms of modifications required in RF front end, signal processing and computing navigation solution.

The main purpose of this study is to develop a new Windows-based program that calculates a quality control parameter that shows the quality of GPS observations using Global Positing Sensing (GPS) data in a Receiver INdependent Exchange (RINEX) format. This new program, Global Positing Sensing Quality Control) (GPSQC), allows general GPS users to easily and intuitively check the quality of GPS observations before post-processing, which will lead to the improvement of GPS positioning precision in diverse areas of GPS applications. The GPSQC is designed to control the multi-path, cycle slip, and ionospheric errors of L1 and L2 signals in GPS observations. The GPSQC was developed using C#.NET language for the Window series with Microsoft Graphical User Interfaces (MS GUIs). This program gives brief information for GPS observations, time series plots, graphs of quality control parameters, and a summary report in MS word, Excel and PDF formats. It can simply perform quality checking of GPS observations that is difficult for surveyors conducting field work. We expect that GPSQC can be used to improve the accuracy of positioning and to solve time-consuming problems due to data loss and large errors in GPS observations.

Permanent GPS network provides an excellent frame of reference for geodetic positioning in Malaysia and several kinematic applications have been carried out by post-processing the data. This research study investigates on the feasibility of having a permanent and reliable GPS control station in UiTM. To achieve this purpose, a minimum construction is carried out by erecting a concrete monument of the reference station on the roof top of a building in UiTM Shah Alam. The observation technique is conducted in Static Mode continuously throughout the period using a Leica SR520 GPS instrument and processed using the SKI-Pro software. To relate with the national coordinate system, additional data were acquired from JUPEM. All the processed results were analyzed and compared with positions from MyRTKnet. The analysis shown that the coordinates derived for this station is consistent within acceptable tolerance. With the ability to view sufficient number of needed satellites twenty four hours a day, a secure location for the instruments, the chosen location is feasible as a control station. It will be used as a reference station by users for their academic purpose and research study. Furthermore, it is hoped that this reference station be a stepping stone for future development of an independent Real Time Kinematic GPS (RTK-GPS) which currently has already been implemented by JUPEM. In addition, the data from the observation will be provided to students through the internet.

Under contract of different German Ministries a test program investigating the combinations of GPS, GLONASS, and Inertial Navigation has been carried out since 1991. Besides other goals, the aim of the project is to investigate the capabilities of GLONASS in comparison to GPS, to realize a combined GLONASS/INS solution and to perform joint processing of GPS and GLONASS raw data. The paper describes the test procedures and presents some of the results. This includes the comparison of DGPS with stand-alone GLONASS and GLONASS/INS under different dynamic situations, e.g., driving tests, flight tests, and also the presentation of results of combined GPS/GLONASS data processing, which was successfully achieved in March '93 for the first time. The results show the potential of the non-SA-degraded GLONASS and the advantage of using both, GPS and GLONASS for combined solutions. >

GPS navigation is the most frequently used technology for determining geographical position of objects. Despite of their popularity currently available consumer GPS receivers do not offer good accuracy. At the Silesian University of Technology the research was done for measuring errors and improving the accuracy of navigation devices. The special device which can be equipped with four GPS navigation receivers has been developed for performing research on accuracy of positioning.

One of the major problems currently facing satellite-based positioning is the atmospheric refraction of the GPS signal caused by the troposphere. The tropospheric effect is much more pronounced at the equatorial region due to its hot and wet conditions. This affects the GPS signal due to the variability of the refractive index, which in turn affects the positional accuracy, especially in the height components. This paper presents a study conducted in the Southern Peninsular Malaysia located at the equatorial region, to investigate the impact of tropospheric delay on GPS height variation. Four campaigns were launched with each campaign lasting for three days. The Malaysian real-time kinematic GPS network (MyRTKnet) reference stations in Johor Bahru were used. GPS RINEX data from these stations were integrated with ground meteorological data observed concurrently from a GPS station located at the Universiti Teknologi Malaysia (UTM), at varying antenna heights for each session of observation. A developed computer program called TROPO.exe based on the Saastamoinen tropospheric delay model was used in estimating the amount of tropospheric delay. The result reveals that, there is inconsistency in the delay variation, reaching maximum delay of 18 m in pseudo-range measurement. The height component shows variations with a maximum value of 119.100 cm and a minimum value of 37.990 cm. The result of the simulated data shows 5.00 m of differences in height gives an effect or improvement of 1.3 mm in signal propagation. This indicates that, tropospheric delay decreases with increase in antenna height.

In this paper the absolute calibration of GPS time receivers with a Spirent GPS/Galileo HW simulator is analyzed and described in detail. The primary step is to calibrate the simulator itself. In this context the most important facts and values which have to be measured are explained. After the calibration of the simulator the receiver is fed with satellite signals generated by the simulator belonging to a standard GPS satellite constellation to determine the absolute offset of the receiver (internal delay) compared to the simulator output. The used GNSS hardware simulator provides GPS and Galileo signals in parallel and therefore additionally can be used for absolute calibration of combined GPS/Galileo or stand alone Galileo time receivers. As there are no such receivers available yet, the precision of the GPS and Galileo pseudoranges determined by a combined GPS/Galileo receiver is analyzed.

GPS is already fully operational by America in orbit about the Earth, while the Galileo is not yet operational by E.U.. But the user receiver equipment should be able to take advantage of both systems to increase accuracy, integrity, and overall performance with as little impact on each other as possible. This paper presents the research and design on a hybrid software-based GPS/Galileo receiver, together with the signal acquisition and tracking processing using a GPS/Galileo software intermediate frequency (IF) architecture. And the software-based integrated receiver architecture eliminates the traditional baseband ASIC and performs all digital signal processing in software. This approach completely separates the analog signal conditioning (in hardware) and the digital signal processing (in software), resulting in significant gain. So it will become increasingly important as new signals from modernized GPS satellites become available and as the Galileo or China's BeiDou system starts operation.

Software defined radios (SDR) are gaining popularity because of the capability of reprogramming them to work under different standards with minimum hardware change. A software radio can be programmed to acquire data from a GPS satellite as well as a GLONASS satellite. This paper describes the implementation of a non-real time GPS software receiver. The receiver was verified to decode a set of non-real time raw GPS data bin on the LI carrier and the civil navigation message using the C/A code that was stored on a hard drive.

Satellite navigation technology is rapidly evolving. The modernisations in GPS, full deployments of GLONASS and GALILEO after 2008 will facilitate the development of new applications, hence opening new markets. It is time to prepare for this new commodity: ubiquitous provision of reliable and accurate positioning and timing services has already started to transform our societies. This paper will give an overview of satellite navigation systems, GPS, GLONASS and GALILEO as well as GPS modernisation which has been carried out fur a few years.

Precise timing is an inherent part of Global Navigation Satellite Systems (GNSS) like GPS, Glonass and in the future Galileo. In the framework of the interoperability and compatibility discussions between the United States and European Union it was agreed that both GPS and Galileo systems will compute and broadcast the mutual time offset between both system's time scales. This information once available in the signal-in-space (SIS) navigation message will enhance users's interoperability achievable with a combined receiver. This paper outlines efforts to harmonize the underlying navigation time scales of both GPS and Galileo to better facilitate a combined navigation solution. It further discusses different implementation solutions for the GPS to Galileo time offset (GGTO) and the working scheme adapted by both sides.

This paper presents the first results obtained processing the Signal-In-Space broadcast by the Galileo In — Orbit Validation Element A (GIOVE-A) satellite, the first experimental Galileo satellite. The paper analyzes both the acquisition and tracking phase of a Galileo software receiver able to process raw samples of the signal collected by means of a commercial front end. Starting from the description of the system set up used to collect the data set the paper introduces the Partial Correlation approach adopted in the acquisition phase and describes the tracking structures used to synchronize the local and the incoming codes. Techniques tailored to the new structure of the Galileo signal have been employed. In fact, the GIOVE-A signal uses novel modulation schemes and it is made of longer spreading codes that required modification to both the acquisition and tracking algorithms usually implemented within a GPS receiver.

A test-bed application, called Map Matched GPS (MMGPS) processes raw GPS output data, from RINEX files, or GPS derived coordinates. This developed method uses absolute GPS positioning, map matched, to locate the vehicle on a road centre-line, when GPS is known to be sufficiently accurate. MMGPS software has now been adapted to incorporate positioning based on odometer derived distances (OMMGPS), when GPS positions are not available. Relative GPS positions are used to calibrate the odometer. If a GPS position is detected to be inaccurate, it is not used for positioning, or for calibrating the odometer correction factor. In OMMGPS, GPS pseudorange observations are combined with DTM height information and odometer positions to provide a vehicle position at ‘1 s’ epochs. The described experiment used GPS and odometer observations taken on a London bus on a predefined route in central of London. Therefore, map matching techniques are used to test GPS positioning accuracy, and to identify grossly inaccurate GPS positions. In total, over 15,000 vehicle positions were computed and tested using OMMGPS. In general, the position quality provided by GPS alone was extremely poor, due to multipath effects caused by the urban canyons of central London, so that odometer positioning was used much more often to position the vehicle than GPS. Typically, the ratio is 7:3 odometer positions to GPS positions. In the case of one particular trip, OMMGPS provides a mean error of position of 8.8 m compared with 53.7 m for raw GPS alone.

For many applications, access to unbiased or error-controlled global positioning system (GPS) observations can be very useful. This paper is devoted to the description of simulated GPS observations generator (SiGOG), a software that simulates GPS observations. It presents the results of tests of SiGOG accuracy using GPS processing software, and demonstrates its successful performance as a differential GPS (DGPS) correction provider., Facultad de Ciencias Astronómicas y Geofísicas

This paper describes an automated method for predicting the number of satellites visible to a GPS receiver, at any point on the earth's surface at any time. Intervisibility analysis between a GPS receiver and each potentially visible GPS satellite are performed using a number of different surface models and satellite orbit calculations. The developed software can work with various ephemeris data, and will compute satellite visibility in real-time. Real-time satellite availability prediction is very useful for mobile applications such as in-car navigation systems, personal navigations systems and LBS. The implement- tation of the method is described and the results are reported.