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Concept: Wide Area Augmentation System


To analyze the match running profile, distance travelled over successive 15 minutes of match-play, heart rates and effindex of professional soccer players with Global Positioning System (GPS) and heart rate (HR) in official competition.

Concepts: Navigation, Global Positioning System, Global navigation satellite system, GPS, Positioning system, Wide Area Augmentation System, Navigational equipment


Large numbers of children and adolescents in Canada, UK and USA are not getting their recommended daily dose of moderate to vigorous physical activity, and are thus more prone to obesity and its ill health effects. Exergames (video games that require physical activity to play) are rapidly gaining user acceptance, and may have the potential to increase physical activity levels among young people. Mobile exergames for GPS (global positioning system)-enabled smartphones and mini-tablets take players outdoors, in the open air, unlike console exergames, e.g., Xbox 360 Kinect exergames, which limit players to playing indoors in front of a TV set. In this paper and its companion ‘Additional file 1’, we review different examples of GPS exergames and of gamified geosocial apps and gadgets (mobile, location-aware apps and devices with social and gamification features), and briefly discuss some of the issues surrounding their use. Further research is needed to document best practices in this area, quantify the exact health and fitness benefits of GPS exergames and apps (under different settings and scenarios), and find out what is needed to improve them and the best ways to promote their adoption by the public.

Concepts: Illness, Navigation, Global navigation satellite system, GPS, Radio navigation, Video game console, Xbox 360, Wide Area Augmentation System


Active commuting may help to increase adults' physical activity levels. However, estimates of its energy cost are derived from a small number of studies which are laboratory-based or use self-reported measures. Adults working in Cambridge (UK) recruited through a predominantly workplace-based strategy wore combined heart rate and movement sensors and global positioning system (GPS) devices for one week, and completed synchronous day-by-day travel diaries in 2010 and 2011. Commuting journeys were delineated using GPS data, and metabolic intensity (standard metabolic equivalents; MET) was derived and compared between journey types using mixed-effects linear regression. 182 commuting journeys were included in the analysis. Median intensity was 1.28 MET for car journeys; 1.67 MET for bus journeys; 4.61 MET for walking journeys; 6.44 MET for cycling journeys; 1.78 MET for journeys made by car in combination with walking; and 2.21 MET for journeys made by car in combination with cycling. The value for journeys made solely by car was significantly lower than those for all other journey types (p<0.04). On average, 20% of the duration of journeys incorporating any active travel (equating to 8 minutes) was spent in moderate-to-vigorous physical activity (MVPA). We have demonstrated how GPS and activity data from a free-living sample can be used simultaneously to provide objective estimates of commuting energy expenditure. On average, incorporating walking or cycling into longer journeys provided over half the weekly recommended activity levels from the commute alone. This may be an efficient way of achieving physical activity guidelines and improving population health.

Concepts: Navigation, Global Positioning System, Global navigation satellite system, GPS, Positioning system, Commuting, Wide Area Augmentation System, Navigational equipment


Accelerometer-based technologies could be useful in providing objective measures of canine ambulation, but most are either not tailored to the idiosyncrasies of canine gait, or, use un-validated or closed source approaches. The aim of this paper was to validate algorithms which could be applied to accelerometer data for i) counting the number of steps and ii) distance travelled by a dog. To count steps, an approach based on partitioning acceleration was used. This was applied to accelerometer data from 13 dogs which were walked a set distance and filmed. Each footfall captured on video was annotated. In a second experiment, an approach based on signal features was used to estimate distance travelled. This was applied to accelerometer data from 10 dogs with osteoarthritis during normal walks with their owners where GPS (Global Positioning System) was also captured. Pearson’s correlations and Bland Altman statistics were used to compare i) the number of steps measured on video footage and predicted by the algorithm and ii) the distance travelled estimated by GPS and predicted by the algorithm.

Concepts: Statistics, Navigation, Walking, Global Positioning System, Global navigation satellite system, GPS, Wide Area Augmentation System, Navigational equipment


Athlete tracking devices that include global positioning system (GPS) and micro electrical mechanical system (MEMS) components are now commonplace in sport research and practice. These devices provide large amounts of data that are used to inform decision-making on athlete training and performance. However, the data obtained from these devices are often provided without clear explanation of how these metrics are obtained. At present, there is no clear consensus regarding how these data should be handled and reported in a sport context. Therefore, the aim of this review was to examine the factors that affect the data produced by these athlete tracking devices to provide guidelines for collecting, processing, and reporting of data. Many factors including device sampling rate, positioning and fitting of devices, satellite signal and data filtering methods can affect the measures obtained from GPS and MEMS devices. Therefore researchers are encouraged to report device brand/model, sampling frequency, number of satellites, horizontal dilution of precision (HDOP) and software/firmware versions in any published research. Additionally, details of data inclusion/exclusion criteria for data obtained from these devices are also recommended. Considerations for the application of speed zones to evaluate the magnitude and distribution of different locomotor activities recorded by GPS are also presented, alongside recommendations for both industry practice and future research directions. Through a standard approach to data collection and procedure reporting, researchers and practitioners will be able to make more confident comparisons from their data, which will improve the understanding and impact these devices can have on athlete performance.

Concepts: Navigation, Global Positioning System, Global navigation satellite system, GPS, Geodesy, Radio navigation, Wide Area Augmentation System, Navigational equipment


The Hatch filter is a code-smoothing technique that uses the variation of the carrier phase. It can effectively reduce the noise of a pseudo-range with a very simple filter construction, but it occasionally causes an ionosphere-induced error for low-lying satellites. Herein, we propose an optimal single-frequency (SF) divergence-free Hatch filter that uses a satellite-based augmentation system (SBAS) message to reduce the ionospheric divergence and applies the optimal smoothing constant for its smoothing window width. According to the data-processing results, the overall performance of the proposed filter is comparable to that of the dual frequency (DF) divergence-free Hatch filter. Moreover, it can reduce the horizontal error of 57 cm to 37 cm and improve the vertical accuracy of the conventional Hatch filter by 25%. Considering that SF receivers dominate the global navigation satellite system (GNSS) market and that most of these receivers include the SBAS function, the filter suggested in this paper is of great value in that it can make the differential GPS (DGPS) performance of the low-cost SF receivers comparable to that of DF receivers.

Concepts: Navigation, Global Positioning System, Global navigation satellite system, GPS, Geodesy, Satellite navigation systems, Differential GPS, Wide Area Augmentation System


In our study, we analyzed the combined standard uncertainty of water table slope assessment done using differential global positioning system (DGPS)-based measurements of water table elevation and distances between measurement locations. We compared and discussed uncertainties in water table slope assessments done in various hypothetical environments of lowland floodplains (water table slopes typically ranged from 1.25 · 10(-4) to 1 · 10(-3)). Our analyses referred to elevation measurements done with the static GPS and DGPS real-time kinematic (RTK) approaches, which are currently among the most frequently used elevation measurement techniques worldwide. Calculations of the combined standard uncertainty of water table slope allowed us to conclude that the DGPS-RTK approach used in water table slope assessment can result in assessment errors as high as 50 % at short (<200 m) distances. Acceptable water table slope measurement errors (lower than 5 %) occur at distances longer than 11,320 m in the case of DGPS-RTK measurements, while, in the case of static GPS measurements, acceptable measurement errors at the same level occur at distances as low as 1350 m. Errors in water table slope assessment as high as 50 % occur at distances of 1130 m and 140 m for DGPS-RTK and static GPS measurements, respectively. We conclude that, although the DGPS-RTK methodology-due to its ease of use and time-saving capabilities is very often applied to water level measurements in lowland riparian wetlands, the application of the DGPS-RTK methodology for water table slope assessment at distances shorter than a few couples of meters results in very low accuracy (errors greater than 50 %) and should not be used for calculating local slopes in low slope areas such as lowland riparian zones.

Concepts: Measurement, Uncertainty, Global Positioning System, Global navigation satellite system, GPS, Geodesy, Differential GPS, Wide Area Augmentation System


With sparse and uneven site distribution, Global Positioning System (GPS) data is just barely able to infer low-degree coefficients in the surface mass field. The unresolved higher-degree coefficients turn out to introduce aliasing errors into the estimates of low-degree coefficients. To reduce the aliasing errors, the optimal truncation degree should be employed. Using surface displacements simulated from loading models, we theoretically prove that the optimal truncation degree should be degree 6-7 for a GPS inversion and degree 20 for combing GPS and Ocean Bottom Pressure (OBP) with no additional regularization. The optimal truncation degree should be decreased to degree 4-5 for real GPS data. Additionally, we prove that a Scaled Sensitivity Matrix (SSM) approach can be used to quantify the aliasing errors due to any one or any combination of unresolved higher degrees, which is beneficial to identify the major error source from among all the unresolved higher degrees. Results show that the unresolved higher degrees lower than degree 20 are the major error source for global inversion. We also theoretically prove that the SSM approach can be used to mitigate the aliasing errors in a GPS inversion, if the neglected higher degrees are well known from other sources.

Concepts: Navigation, Degrees of freedom, Global Positioning System, Surveying, Global navigation satellite system, GPS, Speed of light, Wide Area Augmentation System


Despite the increased professionalism and substantial growth of surfing worldwide, there is limited information available to practitioners and coaches in terms of key performance analytics that are common in other field based sports. Indeed, research analyzing surfing performance is limited to a few studies examining male surfers' heart rates, surfing activities through time-motion analysis (TMA) using video recordings and Global Positioning Satellite (GPS) data during competition and recreational surfing. These studies have indicated that specific activities undertaken during surfing are unique with a variety of activities (i.e. paddling, resting, wave riding, breath holding and recovery of surfboard in the surf. Furthermore, environmental and wave conditions also appear to influence the physical demands of competition surfing. It is due to these demands that surfers are required to have a high cardio-respiratory fitness, high muscular endurance and considerable strength and anaerobic power, particular within the upper torso. By exploring various methods of performance analysis utilised within other sports, it is possible to improve our understanding of surfing demands. In so doing this will assist in the development of protocols and strategies to assess physiological characteristics of surfers, monitor athlete performance, improve training prescription and identify talent. Therefore, this review explores the current literature in order to provide insights into methodological protocols, delimitations of research into athlete analysis and an overview of surfing dynamics. Specifically, this review will describe and review the use of TMA, GPS and other technologies (i.e. HR) that are used in external and internal load monitoring as they pertain to surfing.

Concepts: Global Positioning System, Surfing, Surfboard, Surf culture, Global navigation satellite system, GPS, Geodesy, Wide Area Augmentation System


Introduction: The initial symptoms of Alzheimer’s disease (AD) include attention deficits, memory loss and deficiencies in topographic and spatial orientation. People with AD may have way-finding difficulties in driving due to the deterioration of their navigation ability. Although the use of the Global Positioning System (GPS) has been proven to be a useful aid for older people in driving, there is no evidence to suggest that the benefit could extend to drivers with AD. Aim: This study aims to investigate the effectiveness of the GPS in assisting drivers with mild AD in finding their destination safely. Method: Twenty-eight drivers with mild to very mild AD, diagnosed by a general practitioner or a psychogeriatrician, completed all clinical and psychometric assessments including the Mini Mental State Examination, Trail Making Test B and Doors and People Test. During the driving assessment, 3 driving trials with different settings (normal, visual-only and audio-only) of the GPS were administered to all participants. The participants were required to follow instructions from the GPS and perform a variety of driving tasks on a driving simulator. The driving performances of participants were assessed by criteria specific to AD drivers. The driving assessment criteria were first combined to form the overall driving performance score: a higher score indicated a better overall driving performance. The other outcome of this study was the success of participants to navigate to a predetermined destination. Results: The driving performance of participants was different among the 3 settings (F = 72.8, p < 0.001) and the pairwise comparison between the 3 settings was significant (p < 0.001). The driving performance score was highest in the audio-only setting (mean: 20.0, SD: 2.2), moderate in the normal setting (mean: 16.7, SD: 2.6) and lowest in the visual-only setting (mean: 14.3, SD: 3.3). When compared with the visual-only setting, drivers using the audio-only setting (OR: 37.2, 95% CI: 9.2-151.2) and normal setting (OR: 37.2, 95% CI: 4.8-286.9) were more likely to successfully find their destination (p < 0.05). Conclusion: This study has found that using single, simple auditory instructions with the absence of the visual output of the GPS could potentially help people with mild AD to improve their driving ability and reach their destination. © 2014 S. Karger AG, Basel.

Concepts: Alzheimer's disease, Psychometrics, Navigation, Global Positioning System, Global navigation satellite system, GPS, Geodesy, Wide Area Augmentation System