GPS Software Research Articles

Acquisition of E5 Galileo Signals in Matlab

The deployment of Galileo constellation leads to the need of efficient algorithms for acquisition and tracking of Galileo signals. These signals are different from GPS signals and this difference should be taken into consideration in the program code. This paper deals with the acquisition of Galileo signals in Matlab. The code is developed on the basis of the free code developed by Kai Borre for GPS Software defined radio [1].

Improvement of signal synchronization in GPS software receiver

In GPS receivers, navigation bit allocation is performed throughout the process of signal tracking and detection. In the process of signal tracking, the locally generated signal must be synchronized with the received signal. The Costas phase-locked loop (PLL) behavior, which is often used for signal synchronization, is characterized by dominant tracking error sources. The resulting phase tracking errors are significant in the presence of weak signals, i.e. signals with the low signal-to-noise ratio (SNR). In order to improve the signal synchronization and enable signal tracking by the receiver, we here proposed the usage of a non-data-aided (NDA) phase estimator. Based on the practical processing of the GPS signals, it is shown that the applied NDA algorithm is more resistant to sudden changes in frequency (phase) of the input signal than the previously considered phase discriminator in the Costas PLL. Also, we have shown that the solution analyzed here exhibits more stable operation in signal tracking for a low SNR.

Analysisof Sensoring System Development Process

With the prevalence of the Global Positioning System, an increasing number of electronic devices and vehicles have been equipped with a GPS module for a variety of applications including navigation and location-based search. Early GPS software was developed as monolithic tool in which all functions packed in the same software. But, these GPS software have the problems of the high cost of constructing system. close system architecture and the reusability. And there is a lack of interoperability between them because most of them have their own unique data format according to their application fields. Therefore in the paper new extended for better modeling GPS application in the UML Diagram are proposed, and the Implementation of a program called StereotypeCreator, which is able to create iconic stereotypes used in one of the most popular visual modeling tools for software development, Rational Rose, will be also proposed.

Jamming the Works: Art, Politics and Activism Introduction

As we enter the second decade of the 21st century, art that aims to actively challenge the social order continues to spark controversy and encounter resistance. In one recent instance, the University of California at San Diego threatened to revoke the tenure of Ricardo Dominguez, a professor of visual art, who developed what he calls “transborder immigrant tools”—recycled cell phones loaded with GPS software that point border-crossers to caches of fresh water in the desert. Dominquez has called the phones, which feature an audio application that plays inspirational poetry to migrants, a “mobile Statue of Liberty.”

A Realistic and Easy-to-Implement Weighting Model for GPS Phase Observations

Observation weighting is an essential component of GPS stochastic modeling and plays a key role in reliable outlier detection and parameter estimation. Nowadays, satellite elevation angle and SNR are used as quality indicators for GPS phase measurements in high-accuracy geodetic applications. In comparison with elevation-dependent models, SNR-based weighting schemes represent the reality better, but usually require greater implementation efforts. Relying upon a representative analysis of empirical SNR-based weights, this paper proposes the elevation-dependent exponential weighting function EXPZ, which benefits from realistic SNR-based weights and enables easy software implementation. To process GPS data from a regional network, this advanced weighting scheme is implemented in the Bernese GPS Software 5.0 and is compared with the conventional elevation-dependent COSZ model in terms of phase ambiguity resolution, troposphere parameter (TRP) estimation, and site coordinate determination. The results show that the proposed EXPZ model significantly attenuates the downweighting effects on low-elevation observations and improves the success rates of ambiguity resolution by about 10%, the standard deviations of site-specific TRPs by about 40%, and the repeatability of daily coordinate estimates by up to 2.3 mm (50%).

An Optimized Acquisition Algorithm in GPS Software Receiver

An Optimized Acquisition Algorithm in GPS Software Receiver

Horizontal crustal deformation in Chinese Mainland analyzed by CMONOC GPS data from 2009–2013

Abstract: In this study, we analyze the regional GPS data of Crustal Movement Observation Network of China (CMONOC) observed from 2009–2013 using the BERNESE GPS software, and then the preliminary results of horizontal velocity field and strain rate field are presented, which could reflect the overall deformation features in the Chinese mainland from 2009–2013. Besides, the velocity error and the probable factors that could influence the estimate of long-term deformation are also discussed.

Determination of Optimal River Network from DEM using differential GPS

In this study, the Optimal River Network (ORN) has been determined in a waterlogged area. A dense 3D coordinates obtained from Differential GPS were used to create a Digital Elevation and Digital Terrain Models and their contingents comprising Watershed, Slope, Contours and Aspect. Areas at risk of being flooded are northward, surrounded by lowlying terrain while the south constitute undulating hills with natural river discharge at the centre. The ORN determines an ideal direction of flow of water out of the region, putting into consideration future planning and development. Existing small streams are directed to a permanent flow network to minimise land loss due to erosion and reduce cost of developing building projects in the waterlogged area. It is evident here that Differential GPS and Geographic Information Systems software can be combined to find ideal solutions to natural hazards akin to flood and erosion and even beyond.

Crustal deformation study in the Canary Archipelago by the analysis of GPS observations

AbstractThe Canary Archipelago is an active volcanic region located in the African plate, at 100 Km of the northwest coast of Africa. The Complutense University of Madrid, Institute of Astronomy and Geodesy (CSIC-UCM) and University of Jaén, established a GPS Network in this region and carried out six observations campaigns from 2002 to 2009. The focus of thiswork is processing and analyzing these observations to study the geodynamic behavior of the stations of this network. The data have been computed with the Bernese GPS Software Version 5.0 obtaining individual solutions of coordinates for each session and campaign, the coordinate velocities of the stations and the time series of baselines formed between them. Results show consistency of station velocities compared to behaviour of areas permanent stations and baselines stability. No deformations could be detected.

Effect of the Glonass-Specific Receiver Antenna Phase Center Corrections on the Results of European Regional GNSS Network

ABSTRACT In the paper I investigated the effect of the GLONASS-specific receiver antenna phase center corrections on the results of a regional permanent GNSS network. I made analysis, using Bernese GPS Software 5.0, of GPS-only and GPS-GLONASS (GNSS) observations collected at permanent sites in Europe. Two types of GNSS solutions were computed: with GPS phase center corrections used for observations of both systems, and with the system specific corrections for observations of the respective system. The Bernese software was modified accordingly to use GLONASS specific corrections for GLONASS measurements. The results, i.e., coordinates and tropospheric zenith delays were analyzed and compared between computed solutions. Introducing GLONASS-specific receiver antenna phase center corrections did not improve the repeatability of the GNSS coordinate time series. Differences of coordinates between the two GNSS solutions were highly repeatable but offsets (biases) were observed; maximum bias for horizontal component was 1 mm and 4 mm for up component. Similar biases were observed for stations with the same antenna models. Periodic signal with a period of 1/3-year was found in difference time series between GPS and GNSS solutions for north component with a maximum peak-to-peak amplitude 2.8 mm. The periodic signal was attributed to GLONASS.

New velocity analysis in geodynamic network Sneznik based on GNSS measurement reprocessing using reprocessed IGS products

Since 2006 the International GNSS Service (IGS) started with reprocessing of all IGS products (Steigenberger et al., 2006; Ferland, 2010) according newly adopted models and reference frame. The resulting reprocessed products are of superior quality and homogeneous through the whole time span. Moreover the IGS re-processing made available all the products also for the period before year 2000 when IGS originally started to provide them. The availability of those products was the main motivation for a comprehensive reprocessing of all GNSS data from the Local Geodynamic Sněžnik Network from the period between 1997 and 2011. All calculations were performed in the Bernese GPS software 5.0. The absolute method of Precise Point Positioning (PPP) was used for the first time within the network providing interesting results. The main evaluation of recent movement tendencies was done using common relative method where the nearest IGS points were used as reference points. ARTICLE INFO

GEOSUD/SUDETEN network GPS data reprocessing and site velocity estimations

The geodynamic network of the Sudety Mts. (GEOSUD) was established in Poland in 1996. Simultaneously, the geodynamic network EAST SUDETEN was built on the Czech side in 1997 and, in 2001, it was extended for sites towards west (the WEST SUDETEN network). Since 1997 annual GPS campaign measurements have been performed on GEOSUD and EAST SUDETEN networks. Satellite observations were processed several times using the Bernese GPS Software, versions 4.0, 4.2 and 5.0. Different observation periods were processed applying different models for Earth's rotation, satellite ephemeris, pole motions, ocean loadings and antennas calibrations. This paper describes the result of uniform reprocessing of all measurements carried out in the period 1997-2012. The Bernese GPS Software V5.0 supported by the IGS Final product and absolute antenna phase centre model (IGS Final from 1409 GPS week (REPRO1 from 920 to 1408)) was used for the homogeneous reprocessing. The solution was referenced to the ITRF2008 datum using data from class A stations of the EUREF Permanent Network (EPN). The GEOSUD network was processed at IGG and the EAST and WEST SUDETEN networks at IRSM applying common processing strategy and the same reference EPN stations. Horizontal site velocities were estimated in a minimum constrained solution using ADDNEQ2 module of the Bernese GPS Software V5.0. The ITRF2008 a priori coordinates and velocities were introduced for fiducial stations belonging to EPN network. Estimated ITRF2008 velocities quality assessment was also performed by the comparison with reference EPN and ASG-EUPOS velocities. Final velocities were transformed to the ETRF2000(R08) applying the ITRF2008 plate-motion model. Paper summarizes the horizontal velocity estimations of the GEOSUD, EAST and WEST SUDETEN geodynamic network sites that cover the Sudety area and their tectonic foreland. ARTICLE INFO

GPS를 이용한 미국 알래스카 어거스틴 화산의 지표변위 감시 - 2006년 분화를 중심으로 -

미국 알래스카의 알류산열도에 위치하는 어거스틴 화산은 인근 지역에 위치하는 많은 화산들 중 가장 움직임이 활발한 화산중 하나로, 가장 최근에 발생한 2006년 분화 당시 1월 11일부터 28일까지 총 14번의 분출을 하였으며, 최종적으로 화산폭발지수 3으로 기록되었다. 본 연구에서는 어거스틴에 설치되어 상시운영 중인 12개 GPS 관측소의 2005년부터 2011년까지 관측데이터를 이용하여 2006년 분화 전 후 지표변위 양상을 확인하고 다각도의 분석을 시도하였다. 모든 자료처리는 Bernese GPS Software V5.0를 이용하여 진행하였으며, 어거스틴 화산 인근(약 24.5 km)에 위치한 AC59 관측소를 기지점으로 하는 정밀 기선해석이 수행되었다. 그 결과 분화가 발생하기 약 4개월 전부터 분화구 주변에서 평균 9.7 cm/yr 속도로 지표가 부풀어 오르는 양상이 뚜렷하게 나타났으며, 분화 발생 이후 -9.2 cm/yr의 급격한 침하현상이 확인되었다. 화산활동이 안정기에 접어든 이후에는 화산의 북쪽 사면에 설치된 일부 관측소에서 분화 당시 흘러내린 화산쇄설물의 다짐작용에 의한 침하 현상이 확인되었다. 이러한 결과는 GPS를 이용하여 관측한 지표의 변화가 화산활동을 감시하고 예측하는데 유용한 자료로 사용될 수 있음을 시사한다. Augustine is an active stratovolcano located in southwest of Cook Inlet, about 290 kilometers southwest of Anchorage, Alaska. Between January 11 and 28, 2006, the volcano erupted explosively 14 times. We collected twelve permanent GPS stations operating by Plate Boundary Observatory (PBO) from 2005 to 2011. All data processing was carried out using Bernese GPS Software V5.0 with IGS precise orbit. Static baseline processing by fixing AC59 station was applied for the volcano activity monitoring. AC59 is the nearest (about 24.5 km) station to Augustine volcano, and located on North America Plate including Augustine Island. The test results show inflation (9.7 cm/yr) and deflation (-9.2 cm/yr) of volcano before and after eruption around crater clearly. After volcano activity has reached a plateau, some of the GPS stations installed north of the volcano show ground subsidence phenomenon caused by compaction of pyroclastic flows. These results indicate the possibility of using surface deformation observed by GPS for monitoring and prediction of volcano activity.

New approach for routing in mobile ad‐hoc networks based on ant colony optimisation with global positioning system

The field of mobile ad-hoc networks (MANETs) has gained an important part of the interest of researchers and become very popular in past few years. MANETs can be used to set up a temporary mean of communication by having nodes behave as hosts and routers, with packets hopping between nodes to reach the destination node. This makes MANET suitable for rapid deployment, but because of the dynamic changes in network configurations, quickly finding the optimum route is difficult. In this study, the authors propose a biology-inspired ant routing protocol based on ant colony optimisation called as optimised antnet global positioning system, which is based on GPS and mobile software agents modelled on ants for routing in ad-hoc networks. The authors compare the performance of the authors protocol with Antnet, ad-hoc on-demand distance vector, Dynamic Source Routing (DSR) and Ad-hoc On Demand Multipath Distance Vector (AOMDV) protocols with respect to end-to-end delay, average throughput, packet delivery ratio and route cost.

GPS monitoring of bedrock stability at Olkiluoto nuclear waste disposal site in Finland from 1996 to 2012

Abstract The Finnish Geodetic Institute has studied crustal deformations at Olkiluoto nuclear waste disposal site since mid-90’s. Biannual GPS measurement has been carried out in two local GPS networks. This paper analyses the GPS data processing effects on the coordinate solutions and presents the results of GPS monitoring from 1996 to 2012. The GPS data was processed using Bernese GPS Software 5.0. The GPS data processing and baseline analysis showed a 1.0 mm (max RMS) level agreement of observation and high bedrock stability in the area. Most of the horizontal trends were smaller than 0.1 mm/a. The troposphere estimation strategy had a clear effect on the horizontal trends at some sites. The strain rates were all very small, but we could detect motions near the Olkiluoto permanent station.

Near-real-time regional troposphere models for the GNSS precise point positioning technique

The GNSS precise point positioning (PPP) technique requires high quality product (orbits and clocks) application, since their error directly affects the quality of positioning. For real-time purposes it is possible to utilize ultra-rapid precise orbits and clocks which are disseminated through the Internet. In order to eliminate as many unknown parameters as possible, one may introduce external information on zenith troposphere delay (ZTD). It is desirable that the a priori model is accurate and reliable, especially for real-time application. One of the open problems in GNSS positioning is troposphere delay modelling on the basis of ground meteorological observations. Institute of Geodesy and Geoinformatics of Wroclaw University of Environmental and Life Sciences (IGG WUELS) has developed two independent regional troposphere models for the territory of Poland. The first one is estimated in near-real-time regime using GNSS data from a Polish ground-based augmentation system named ASG-EUPOS established by Polish Head Office of Geodesy and Cartography (GUGiK) in 2008. The second one is based on meteorological parameters (temperature, pressure and humidity) gathered from various meteorological networks operating over the area of Poland and surrounding countries. This paper describes the methodology of both model calculation and verification. It also presents results of applying various ZTD models into kinematic PPP in the post-processing mode using Bernese GPS Software. Positioning results were used to assess the quality of the developed models during changing weather conditions. Finally, the impact of model application to simulated real-time PPP on precision, accuracy and convergence time is discussed.

Real-time clock jump compensation for precise point positioning

Over the past decades, a number of methods have been proposed to handle cycle slips in the carrier phase measurements, but few researches have investigated receiver clock jumps, which may produce undesirable effects on GPS data processing. Such events are generally ignored in double-differenced positioning. For undifferenced processing, such as precise point positioning (PPP) techniques, it is unwise to neglect the impact of clock jumps. Failure to properly detect and account for receiver clock jumps may sometimes cause unexpected behavior of the GPS software and large errors in the resulting PPP solution. This is particularly troublesome when there are irregular (types 2 or 3) millisecond clock jumps represented in RINEX observation files. In this study, we first provide an intuitive description of the receiver clock jump phenomenon, and a comprehensive classification of clock jumps is presented according to its influence on three fundamental quantities (time tag, pseudorange, and carrier phase) of RINEX observation files. To follow the RINEX convention, the observable consistency is analyzed for various types of clock jump; and a simple but robust real-time clock jump compensation (RTCJC) method is proposed for reconstructing a consistent set of observables. Numerous validation tests with various GPS data show that the method is applicable to millisecond clock jumps. Without RTCJC, clock jumps are prone to cause failure of gross error and cycle slip detection algorithms and so result in repeated re-initialization or even non-convergent solutions, which lead to gross errors in the PPP solution. When RTCJC is applied, all clock jumps present in the GPS data can be effectively identified and repaired accurately, and the problem of re-initialization in PPP will no longer be triggered by receiver clock jumps, which results in significant improvement of PPP accuracy and reliability.

Long-term analysis of tropospheric delay and ambiguity resolution rate of GPS data

Long-term GPS data analysis was performed in order to analyze the seasonal variation of tropospheric delay and the success rate of the ambiguity resolution. For this analysis, a total of 57 stations including 10 IGS stations in East Asia were processed together with double-differenced observables using Bernese GPS Software V5.0. The time span for this study ranges from 2002.0 to 2012.5 (10.5 years). The average baseline length is 339.0 km and the maximum reaches up to 2,000 km. The analysis is focused on two things: the annual variation of the tropospheric delay and the ambiguity resolution rate. The tropospheric delay is closely related to the weather condition, especially relative humidity, therefore it was estimated that the maximum would be in summer, while reaching its minimum in winter with the apparent seasonal variations. On the contrary, however, the success rate of the ambiguity resolution shows the opposite pattern: its maximum was in winter and minimum in summer. The fact seems to be induced by the surrounding conditions; that is, the trees thick with leaves near the GPS antenna interfere with GPS signals in summer. This seems to confirm partly that there is a distinct trend in the decreasing success rate since 2006 because the trees are growing every year. It is necessary to eliminate the factors that degrade the GPS quality and the tropospheric modeling for Korea needs to be studied further.

GPS 소프트웨어 수신기에 대한 GPS 의사위성의 영향 분석

이 논문은 의사위성 신호에 대한 GPS 소프트웨어 수신기의 성능을 분석하고자 한다. 의사위성이 계속 켜져있을 경우와 펄싱이 주어졌을 경우에 대해서, 의사위성의 신호세기와 의사위성과 수신기 사이의 거리에 따라 의사위성이 GPS 소프트웨어 수신기에 미치는 영향을 알아본다. This paper considers the performance of the non-participating GPS software receivers under the presence of GPS pseudolite(PL). For the continuous PL signal and pulsed PL signal, the impact of PL signals on the GPS software receivers is investigated according to the signal strength of the PL and the distance between the PL and the GPS receiver.

Extracting Ionosphere Scintillations Index Based on Single Frequency GPS Software Receiver

Scintillations are caused by ionospheric plasma-density irregularities and can lead to signal power fading, loss of lock of the carrier tracking loop in the GPS receiver. The traditional method of monitoring and mitigating scintillation is to transform commercial GPS receiver with modified hardware and embedded software. To better facilitate advance development GPS receiver under different condition, GPS software scintillation receiver is designed in this paper. The hardware scheme of high-speed GPS signal acquisition system is first discussed and implemented with FPGA and DSP architecture. Then, we describe receiver software processing algorithm, particularly the portion involving the scintillation signal acquisition and tracking, ionospheric scintillation index extracting and scintillation monitoring. The performance of software receiver is demonstrated under scintillation conditions. Relevant results show that software-receiver based approach can avoid weak signal loss and extract effectively ionospheric scintillation parameter compared with the traditional extracting method. Software receiver is suitable and reliable for the ionospheric scintillations monitoring, and can provide theoretical foundations and experimental preparations for future scintillation studies implemented with Chinese indigenous BeiDou-Ⅱ navigation and poisoning system.