DIRECT GEOREFERENCING OF UAVS

UAV systems have become an attractive data acquisition platform in emerging applications. As measuring instrument they extend the lineup of possible surveying methods in the field of geomatics. However, most of UAVs are equipped with low-cost navigation sensors such as GPS or INS, allowing a positioning accuracy of 3 to 5 m. As a result the acquired position- and orientation data fea- tures a low accuracy which implicates that it cannot be used in applications that require high precision data on cm-level (e.g. direct georeferencing). In this paper we will analyze the potential of differential post-processing of GPS data from UAV in order to im- prove the positioning accuracy for applications basing on direct georeferencing. Subsequently, the obtained results are compared and verified with a track of the octocopter carried out with a total station simultaneously to the GPS data acquisition. The results show that the differential post-processing essentially improved the accuracy of the Falcon position data. Thereby the average offset be- tween the data sets (GPS data, track) and the corresponding standard deviation is 0.82 m and 0.45 m, respectively. However, under ideal conditions it is even possible to improve this positioning accuracy to the cm-range. Furthermore, there are still several sources of error such as the offset between the GPS antenna of the Falcon 8 and the prism which is used for the track. Considering this fact there is further room for improvement regarding the here discussed positioning method

Synergy of CP-DGPS, Accelerometry and Magnetic Sensors for recise Trajectography in Ski Racing

This paper presents the conceptual and technical aspects of a system in development that precisely determines athlete's trajectory through a course. Carrier phase-based (CP-DGPS) positioning represents core of the system, while tri-acial accelerometer and magnetic sensors act as an autonomous aid that offers instantaneous attitude determination and can potentially help when navigating through GPS signal blackout zones

The effect of different global navigation satellite system methods on positioning accuracy in elite alpine skiing

This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.In sport science, Global Navigation Satellite Systems (GNSS) are frequently applied to capture athletes’ position, velocity and acceleration. Application of GNSS includes a large range of different GNSS technologies and methods. To date no study has comprehensively compared the different GNSS methods applied. Therefore, the aim of the current study was to investigate the effect of differential and non-differential solutions, different satellite systems and different GNSS signal frequencies on position accuracy. Twelve alpine ski racers were equipped with high-end GNSS devices while performing runs on a giant slalom course. The skiers’ GNSS antenna positions were calculated in three satellite signal obstruction conditions using five different GNSS methods. The GNSS antenna positions were compared to a video-based photogrammetric reference system over one turn and against the most valid GNSS method over the entire run. Furthermore, the time for acquisitioning differential GNSS solutions was assessed for four differential methods. The only GNSS method that consistently yielded sub-decimetre position accuracy in typical alpine skiing conditions was a differential method using American (GPS) and Russian (GLONASS) satellite systems and the satellite signal frequencies L1 and L2. Under conditions of minimal satellite signal obstruction, valid results were also achieved when either the satellite system GLONASS or the frequency L2 was dropped from the best configuration. All other methods failed to fulfill the accuracy requirements needed to detect relevant differences in the kinematics of alpine skiers, even in conditions favorable for GNSS measurements. The methods with good positioning accuracy had also the shortest times to compute differential solutions. This paper highlights the importance to choose appropriate methods to meet the accuracy requirements for sport applications.Seksjon for fysisk prestasjonsevne / Department of Physical Performanc

Trajectographie de courses de ski alpin avec GPS

Jusqu'à présent, les seules informations disponibles pour l'analyse des courses de ski se limitent aux temps intermédiaires et aux images vidéo. Bien que très spectaculaire pour le téléspectateur, une analyse vidéo (telle qua la technologie SimulCam de Darfish) ne fournit que des informations qualitatives et partielles. L'utilisation de la technique GPS permet d'obtenir des informations quantitatives très précises de trajectoire couvrant l'intégrité de la course

Inter-limb differences in upper quarter mobility/stability are not associated with performance in competitive swimmers

BackgroundThe Y Balance Test–Upper Quarter (YBT–UQ) is a cost-effective, well-established, closed kinetic chain test to assess inter-limb asymmetries in the upper quarter that could negatively affect swimming performance. Thus, the aim of the present study was to determine YBT–UQ performances and inter-limb differences as well as its association with swimming performance in athletes with diverging levels of expertise.MethodsForty female and male competitive swimmers (age range: 10–22 years) with different expertise levels (A-squad: n = 9, B-squad: n = 12, C-squad: n = 19) were tested (reach distances for the YBT–UQ) and swimming performance was calculated using the ratio of individual to world best time.ResultsYBT–UQ performances (i.e., inferolateral reach direction for the dominant arm: p = .027, ηp2 = .12 and the non-dominant arm: p = .031, ηp2 = .17) but not YBT–UQ inter-limb differences significantly differed between groups and were largest in swimmers with the lowest expertise level (i.e., C-squad). Further, YBT–UQ performances (i.e., inferolateral reach direction [r = −.68 to −.70, both p < .05] and composite score [r = −.65 to −.67, both p < .05] for both arms and medial reach direction for the non-dominant arm [r = −.64, p < .05]) but not inter-limb differences were significantly and negatively correlated with swimming performance among B-squad swimmers.ConclusionsOur results suggest that inter-limb differences in upper quarter mobility/stability are not influenced by the level of expertise and have no significant associations with swimming performance. However, greater reach distances were correlated with lower swimming performance for the B-squad swimmers indicating that a training-related increase in upper quarter mobility/stability could worsen swimming performance in those athletes

Heat Integration Study of CO2 Capture in Blue Hydrogen Production

Hydrogen is an energy carrier that can be used to develop a low-carbon economy: the hydrogen-based industry. For this purpose, a source of hydrogen is needed. Steam methane reforming (SMR) is the current benchmark to produce hydrogen. This technology combines high efficiency and low production cost; however, it is CO2-intensive. Integrated with carbon capture, SMR could provide a low carbon H2, (blue Hydrogen). This paper studies the potential of an offshore blue hydrogen production with heat integration allowing recovery of heat in the SMR process to use in the CO2 capture process. For the studied case, the heat integration shows that almost half of CO2 can be captured based on chemical absorption with 30wt% MEA. Finally, an economic evaluation discusses the cost of hydrogen production highlighting that CO2 taxes play a crucial role

Sensors / The effect of different Global Navigation Satellite System methods on positioning accuracy in elite alpine skiing

In sport science, Global Navigation Satellite Systems (GNSS) are frequently applied to capture athletes' position, velocity and acceleration. Application of GNSS includes a large range of different GNSS technologies and methods. To date no study has comprehensively compared the different GNSS methods applied. Therefore, the aim of the current study was to investigate the effect of differential and non-differential solutions, different satellite systems and different GNSS signal frequencies on position accuracy. Twelve alpine ski racers were equipped with high-end GNSS devices while performing runs on a giant slalom course. The skiers' GNSS antenna positions were calculated in three satellite signal obstruction conditions using five different GNSS methods. The GNSS antenna positions were compared to a video-based photogrammetric reference system over one turn and against the most valid GNSS method over the entire run. Furthermore, the time for acquisitioning differential GNSS solutions was assessed for four differential methods. The only GNSS method that consistently yielded sub-decimetre position accuracy in typical alpine skiing conditions was a differential method using American (GPS) and Russian (GLONASS) satellite systems and the satellite signal frequencies L1 and L2. Under conditions of minimal satellite signal obstruction, valid results were also achieved when either the satellite system GLONASS or the frequency L2 was dropped from the best configuration. All other methods failed to fulfill the accuracy requirements needed to detect relevant differences in the kinematics of alpine skiers, even in conditions favorable for GNSS measurements. The methods with good positioning accuracy had also the shortest times to compute differential solutions. This paper highlights the importance to choose appropriate methods to meet the accuracy requirements for sport applications.(VLID)157451

PEPs Group: Products, Environment and Processes

At the University of Liège, the PEPs group contributes to this transition through research in chemical and energy process engineering. Our work focuses on CO2 capture and utilization, Power-to-Fuel systems, and the design of low-carbon industrial solutions. This poster highlights ongoing projects combining lab-scale experiments, process modeling, and pilot development to support decarbonization in industry

Seismic characterization of a rapidly-rising jökulhlaup cycle at the A.P. Olsen Ice Cap, NE-Greenland

Rapidly-rising jökulhlaups, or glacial outburst floods, are a phenomenon with a high potential for damage. The initiation and propagation processes of a rapidly-rising jökulhlaup are still not fully understood. Seismic monitoring can contribute to an improved process understanding, but comprehensive long-term seismic monitoring campaigns capturing the dynamics of a rapidly-rising jökulhlaup have not been reported so far. To fill this gap, we installed a seismic network at the marginal, ice-dammed lake of the A.P. Olsen Ice Cap (APO) in NE-Greenland. Episodic outbursts from the lake cause flood waves in the Zackenberg river, characterized by a rapid discharge increase within a few hours. Our 6 months long seismic dataset comprises the whole fill-and-drain cycle of the ice-dammed lake in 2012 and includes one of the most destructive floods recorded so far for the Zackenberg river. Seismic event detection and localization reveals abundant surface crevassing and correlates with changes of the river discharge. Seismic interferometry suggests the existence of a thin basal sedimentary layer. We show that the ballistic part of the first surface waves can potentially be used to infer medium changes in both the ice body and the basal layer. Interpretation of time-lapse interferograms is challenged by a varying ambient noise source distribution.ISSN:0022-1430ISSN:1727-565