Soil salinity mapping with electromagnetic induction and satellite-based navigation methods

Training prescription and monitoring of team-sport athletes rely on accurate quantification of player movement. Our aim was to determine the sensitivity, reliability and construct validity of measures derived from a wearable device incorporating Global Positioning System (GPS) and accelerometer technology to quantify the peak periods of rugby competition. Match movement data were collected from 30 elite and 30 sub-elite rugby union players across respective competitive seasons. Accelerometer and GPS measures were analysed using a rolling average to identify peak movement for epochs ranging from 5 to 600 seconds. General linear mixed modelling was used to quantify the effects of playing position and match-half on the peak movement and variabilities within and between players represented reliability of each measure. Mean positional differences and match-half changes were assessed via standardisation and magnitude-based decisions. Sensitivity of measures was quantified via evaluation of ("signal") and typical error of measurement ("noise"). GPS and accelerometer measures had poor sensitivity for quantifying peak movement across all epochs and both levels of rugby union competition (noise 4× to 5× the signal). All measures displayed correspondingly low reliability across most epochs and both levels of competition (ICC<0.50). Construct validity was evident in mean differences between playing positions and match halves that were consistent with expected activity profiles in rugby union. However, it was clear from the pattern of differences across epoch durations and levels of competition that GPS and accelerometer measures provided different information about player movement. The poor sensitivity and low reliability of GPS and accelerometer measures of peak movement imply that rugby union players need to be monitored across many matches to obtain adequate precision for assessing individuals. Although all measures displayed construct validity, accelerometers provided meaningful information additional to that of GPS. We recommend using accelerometers alongside GPS to monitor and prescribe match respresentative training.

Integrating Passive Millimeter Wave camera (PMMW), Global Positioning System (GPS), and Differential Global Positioning System (DGPS) provides a pilot with a visual precision approach and landing in inclement weather conditions conceivably down to CAT III conditions. A DARPA funded, NASA Langley managed Technology Reinvestment Program (TRP) consortium consisting of Honeywell, TRW, Boeing, and Composite Optics Corporations is demonstrating the PMMW camera. The TRW developed PMMW camera displays the runway through fog, smoke, and clouds in day or night conditions. The Global Air Traffic Program Office entered into a Cooperative Research and Development Agreement (CRDA) with Honeywell to demonstrate DGPS. The Honeywell developed DGPS provides precision navigational data to within 1 m error where GPS has 100 m of error. In inclement weather the runway approach is initiated using GPS data until a range where DGPS data can be received. The runway is presented to the pilot using the PMMW image viewed via a Heads Up Display (HUD) or Head Mounted Display (HMD). At a range where DGPS data is available, a precise runway and horizon symbology is computed in the Flight Display Computer and overlaid on the PMMW image. Image processing algorithms operate on the PMMW image to identify and highlight obstacles on the runway. The integrated system provides the pilot with an enhanced situation awareness of the runway approach in inclement weather. When a DGPS ground station is not available at the landing area, image processing algorithms (again operating on the PMMW image) generate the runway and horizon symbology. GPS provides the algorithm with initial conditions for runway location and perspective. The algorithm then locates and highlights the runway and any obstacles on the runway. Honeywell Technology Center is performing research in the area of integrating the PMMW, DGPS, and GPS technologies to provide the pilot with the most necessary features of each system; namely: visibility, accuracy, obstacle detection, runway overlay, horizon symbology and availability.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Information communication technology related vehicle services need to support location and the transmission of communication and traffic information between vehicles, or between vehicles and infrastructure. In particular, the technology for the measurement of the accurate location of a vehicle is dependent on location-determination technology like Global Positioning System, and this technology is very important for vehicle driving and location services. If, however, a vehicle is in a Global Positioning System radio-shadow area, neither a Global Positioning System nor a Differential Global Positioning System can accurately measure the corresponding location because of a high error rate caused by the shadowing intervention. Even an Inertial Measurement Unit could provide inaccurate location data due to sensor drift faults around corners and traffic-road speed dumps. Vehicles, therefore, need an absolute location to prevent the provision of inaccurate vehicle-location data that is due to radio-shadow areas and relational Inertial Measurement Unit positions. To achieve this, we assume that vehicle-to-infrastructure communication is possible between a vehicle and roadside unit in Vehicular Ad hoc Networks. We used iBeacon at the roadside unit and revised its Universally Unique Identifier so that it generates absolute Global Positioning System location data; that is, moving vehicles can receive absolute Global Positioning System data from the roadside unit-based iBeacon. We compared the proposed method with current Global Positioning System and Inertial Measurement Unit systems for the following two cases: one with a radio-shadow area and one without. We proved that the proposed method generates location data that are more accurate than those of the other methods.

Constraints on 2004 Sumatra–Andaman earthquake rupture from GPS measurements in Andaman–Nicobar Islands

Effects of physical correlations on long-distance GPS positioning and zenith tropospheric delay estimates

We present analysis results for Global Positioning System (GPS) measurements made at sites in Costa Rica during two campaigns in February and July 1991. GPS solutions for 5 sites (Limon, Liberia, Bratsi, ETCG, and Vueltas) reveal significant horizontal and vertical displacements relative to their February positions. Horizontal displacements relative to Liberia, measured 244.7 ± 0.8, 89.2 ± 0.9, 12.4 ± 1.3, and 1.9 ± 0.9 cm at Limon, Bratsi, Vueltas, and ETCG respectively. Vertical displacements relative to Liberia measured 163 ± 2.1, 15.3 ± 3.0, −10.5 ± 4.4, and −0.6 ±2.1 cm at Limon, Bratsi, Vueltas, and ETCG respectively. We find differences in the GPS derived vertical and horizontal displacements compared to other types of geodetic measurements of uplift in the coastal region and their associated models. To address these differences we compute a dislocation model which fits the GPS measured displacements. A simple uniform planar slip model can not reconcile the differences between the coastal uplift data or the seismic moment, suggesting considerable complexity of the earthquake source.

The main component of Global Positioning System (GPS) positioning error results from time and space varying conditions of radio wave propagation, which depend on atmospherics, disturbances in the satellite constellation, orbit stability, and also due to the U. S. military intentionally such as Selective Availability (SA), among other things. The error caused by the transmitter and receiver operation precision or time-measurement accuracy is negligible. A method for GPS precision enhancement commonly used by civil users is the Differential GPS (DGPS). If DGPS service is interrupted, it will lead to the degraded navigation performance. This paper focuses on applying a Π-Σ Neural Network (PSNN) model to predict Pseudo-Range Corrections (PRC) for DGPS. A low cost commercial module (Rockwell single-frequency GPS receiver) is employed to represent the improvement in DGPS. Experimental results show the proposed NN can online predict the PRC precisely when the PRC signal is lost for a short period of time.

TH-2 is China’s first short-range satellite formation system used to realize interferometric synthetic aperture radar (InSAR) technology. In order to achieve the mission goal of InSAR processing, the relative orbit must be determined with high accuracy. In this study, the precise relative orbit determination (PROD) for TH-2 based on global positioning system (GPS), second-generation BeiDou navagation satellite system (BDS2), and GPS + BDS2 observations was performed. First, the performance of onboard GPS and BDS2 measurements were assessed by analyzing the available data, code multipath errors and noise levels of carrier phase observations. The differences between the National University of Defense Technology (NDT) and the Xi’an Research Institute of Surveying and Mapping (CHS) baseline solutions exhibited an RMS of 1.48 mm outside maneuver periods. The GPS-based orbit was used as a reference orbit to evaluate the BDS2-based orbit and the GPS + BDS2-based orbit. It is the first time BDS2 has been applied to the PROD of low Earth orbit (LEO) satellite formation. The results showed that the root mean square (RMS) of difference between the PROD results using GPS and BDS2 measurements in 3D components was 2.89 mm in the Asia-Pacific region. We assigned different weights to geostationary Earth orbit (GEO) satellites to illustrate the impact of GEO satellites on PROD, and the accuracy of PROD was improved to 7.08 mm with the GEO weighting strategy. Finally, relative orbits were derived from the combined GPS and BDS2 data. When BDS2 was added on the basis of GPS, the average number of visible navigation satellites from TH-2A and TH-2B improved from 7.5 to 9.5. The RMS of the difference between the GPS + BDS2-based orbit and the GPS-based orbit was about 1.2 mm in 3D. The overlap comparison results showed that the combined orbit consistencies were below 1 mm in the radial (R), along-track (T), and cross-track (N) directions. Furthermore, when BDS2 co-worked with GPS, the average of the ambiguity dilution of precision (ADOP) reduced from 0.160 cycle to 0.153 cycle, which was about a 4.4% reduction. The experimental results indicate that millimeter-level PROD results for TH-2 satellite formation can be obtained by using onboard GPS and BDS2 observations, and multi-GNSS can further improve the accuracy and reliability of PROD.

Position determination using satellite navigation system has grown significantly. It provides geospatial with global coverage called GNSS (Global Navigation System Satellite). GNSS satellites consists of GLONASS, GPS (Global positioning system) and Galileo.GPS is the most commonly used system and it is known to its capability to determine 3D position on the surface of the earth. In order to determine the position, a GPS receiver must be able to receive signals from at least four GPS satellites. However, the determination of position in condensed areas such as tunnels, area surrounded by high rise buildings, highly forested and in other closely-knit areas is not achieved because satellite signals cannot reach the receiver in the above-mentioned areas and also others where the signals are reflected before being received by a GPS receiver. In this paper, we present the algorithm to fuse GPS and the inertial measurement unit (IMU) to enable positioning in the above-mentioned Condensed Areas. The standard deviations of the two measurements show that GPS-IMU is better than GPS alone, the standard deviation when satellite outages occurred is - 4.57475 for GPS-IMU measurements and 0.218675 for GPS observations. We presented the results in graphics and it shows that GPS measurements are easily disturbed by external influence such as multipath but GPS-IMU graphic is continuous and robust. The advantages and disadvantages of GPS and INS are complementary and make them work together to enable the accurate measurements in the areas mentioned above. Integration of INS and GNSS can be classified into three types, loosely coupled Kalman filter, tightly coupled Kalman filters and ultratight coupled Kalman filter. In this research we used loosely coupled Kalman filter and tightly coupled Kalman filters to combine GPS and INS in one system.

The capabilities of Ashtech XII for differential GPS (Global Positioning System) are discussed. Differential algorithms and communication protocols to exchange differential information between receivers are included in the internal software of the receiver. Hence, there is no need for external computers to provide the protocol link. The all-in-view capability of the receivers makes them suitable for reference stations as well as remotes. Integration of ASHTECH XII with the vehicle tracking system (VTS) is presented. Differential GPS messages are transferred via the VTS communication link. The integration of the VTS and differential GPS has resulted in an accurate vehicle tracking and positioning system called differential GPS/VTS.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Seismic Hazard at the New Madrid Seismic Zone

For improved localization around the indoor/outdoor transit area of buildings, this paper proposes an efficient algorithm combining the measurements from the WLAN (Wireless Local Area Network) and the GPS (Global Positioning System) for. The proposed hybrid localization algorithm considers both multipath errors and NLOS (Non-Line-of-Sight) errors, which occur in most wireless localization systems. To detect and isolate multipath errors occurring in GPS measurements, the propose algorithm utilizes conventional multipath test statistics. To convert WLAN signal strength measurements to range estimates in the presence of NLOS errors, a simple and effective calibration algorithm is designed to compute conversion parameters. By selecting and combining the reliable GPS and WLAN measurements, the proposed hybrid localization algorithm provides more accurate location estimates. An experiment result demonstrates the performance of the proposed algorithm.

The Global Positioning system (GPS) is used for navigation and associated tasks in wide variety of applications. One of the primary modes of GPS operation is differential GPS. Differential GPS allows more accurate positioning than stand-alone GPS. Many new applications are possible because of the increased accuracy obtained through differential GPS. In this paper the techniques and methods of differential GPS along with the algorithms are discussed which are providing more accurate and precise positioning in recent trends of communication. The purpose of the paper is to introduce the principles of differential GPS theory, and to provide a background for more advanced material.

A real-time integrated navigation system with 2-cm position accuracy was developed using commercial off-the shelf (COTS) equipment including inertial sensors and differential Global Positioning System (GPS) receivers, and was demonstrated for transportation applications with an emphasis on lane departure detection. A 900-MHz radiofrequency communications link transmits GPS base station range and carrier phase measurements to a GPS receiver on the vehicle. The GPS receiver calculates the vehicle position relative to the surveyed base location. The loosely coupled eight-state extended Kalman filter with 10-Hz navigation aids provides smoothed position information between 2-Hz GPS updates and provides graceful degradation in the presence of GPS blockages or communication dropouts. Currently, the navigation aids include anti-lock braking system wheel turns, electronic compass heading and pitch, and map vertical height. Data acquisition and Kalman filtering systems were developed to handle real-time processing and recording of all instrument data for further post-test system evaluation to determine the optimum configuration. An accurate rapid survey and map representation approach for measuring lane boundaries was validated using a vehicle, demonstrating inherit repeatability by the GPS positioning system. Real-time lane departure monitoring was developed. A video camera was installed to assist in accurate surveying and real-time system validation. This GPS-based positioning system is suitable for highway speeds during all weather conditions. It can be extended to other collision avoidance, drowsy driver awareness, advanced curve or intersection warnings, SOS, tracking, automated control, fast precision road mapping, and traffic management applications.

The difference in ionospheric delay between paths to the reference and mobile stations for differential GPS has been quantified for equatorial region. This small additional ionospheric error can be evaluated and predicted for the mobile station by means of a determined differential delay along the baseline so that accurate correction can be made for the most precise positioning. In this paper we studies the ionospheric delay on the Global Positioning System (GPS) signal due to the variation of elevation angle and variation in total electron content (TEC) and ionospheric profiles utilizing the Modified Jones 3D Ray Tracing method. The differential delay can be determined for any azimuth angle of propagation and for any baseline direction, providing the approximate difference in line-of-sight (LOS) between the stations. Result show that the variations of elevation angle and TEC give effects on the difference in delay between the two stations in differential GPS (dGPS). This analysis determined the difference in ionospheric delay expected over a short baseline so that a more accurate differential GPS correction can be made.