scholarly journals Kinematic Determination of the Aerial Phase in Ski Jumping

Sensors ◽  
2022 ◽  
Vol 22 (2) ◽  
pp. 540
Author(s):  
Ola Elfmark ◽  
Gertjan Ettema ◽  
Petter Jølstad ◽  
Matthias Gilgien
Keyword(s):  
Satellite System ◽  
Performance Level ◽  
Rate Of Change ◽  
World Cup ◽  
Physical Point ◽  
Ski Jumping ◽  
And Performance ◽  
Global Navigation Satellite ◽  
Drag Ratio

The purpose of this study was to find a generic method to determine the aerial phase of ski jumping in which the athlete is in a steady gliding condition, commonly known as the ‘stable flight’ phase. The aerial phase of ski jumping was investigated from a physical point mass, rather than an athlete–action-centered perspective. An extensive data collection using a differential Global Navigation Satellite System (dGNSS) was carried out in four different hill sizes. A total of 93 jumps performed by 19 athletes of performance level, ranging from junior to World Cup, were measured. Based on our analysis, we propose a generic algorithm that identifies the stable flight based on steady glide aerodynamic conditions, independent of hill size and the performance level of the athletes. The steady gliding is defined as the condition in which the rate-of-change in the lift-to-drag-ratio (LD-ratio) varies within a narrow band-width described by a threshold τ. For this study using dGNSS, τ amounted to 0.01s−1, regardless of hill size and performance level. While the absolute value of τ may vary when measuring with other sensors, we argue that the methodology and algorithm proposed to find the start and end of a steady glide (stable flight) could be used in future studies as a generic definition and help clarify the communication of results and enable more precise comparisons between studies.

scholarly journals Wind Gust Measuring at Low Altitude Using An Unmanned Aerial System

2021 ◽  
Author(s):  
Alton Yeung
Keyword(s):  
Turbulence Models ◽  
Satellite System ◽  
Data System ◽  
Measurement Unit ◽  
Wind Gust ◽  
Wind Gusts ◽  
Low Altitude ◽  
And Performance ◽  
Global Navigation Satellite ◽  
Aerial Platform

A small unmanned aerial vehicle (UAV) was developed with the specific objective to explore atmospheric wind gusts at low altitudes within the atmospheric boundary layer (ABL). These gusts have major impacts on the flight characteristics and performance of modern small unmanned aerial vehicles. Hence, this project was set to investigate the power spectral density of gusts observed at low altitudes by measuring the gusts with an aerial platform. The small UAV carried an air-data system including a fivehole probe that was adapted for this specific application. The air-data system measured the local wind gusts with an accuracy of 0.5 m/s by combining inputs from a five-hole probe, an inertial measurement unit, and Global Navigation Satellite System (GNSS) receivers. Over 20 flights were performed during the development of the aerial platform. Airborne experiments were performed to collect gust data at low altitudes between 50 m and 100 m. The result was processed into turbulence spectrum and the measurements were compared with the MIL-HDBK-1797 von K´arm´an turbulence model and the results have shown the model underpredicted the gust intensities experienced by the flight vehicle. The anisotropic properties of low-altitude turbulence were also observed when analyzing the measured gusts spectra. The wind and gust data collected are useful for verifying the existing turbulence models for low-altitude flights and benefit the future development of small UAVs in windy environment.

scholarly journals Determination of Conversion Constant between Lagos Datum and Niger Delta Mean Lower Low Water Datum and their Horizontal and Vertical Accuracy Standards using GNSS Observations

2018 ◽  
Vol 2 (1) ◽  
pp. 56-68
Author(s):  
M. O. Ehigiator ◽  
S. O. Oladosu
Keyword(s):  
Niger Delta ◽  
Satellite System ◽  
Constant Factor ◽  
Common Mean ◽  
Height Determination ◽  
The Mean ◽  
Vertical Accuracy ◽  
Global Navigation Satellite ◽  
Gnss Observations

With the use of Global Navigation Satellite System (GNSS) technology, it is now possible to determine the position of points in 3D coordinates systems. Lagos datum is the most common Mean Sea Level used in most parts of Nigeria. In Niger Delta, for instance Warri and its environs, the most commonly used datum for height determination is the Mean Lower Low Water Datum. It then becomes necessary to determine a constant factor for conversion between the two datum when the need arises as both are often encountered during Geomatics Engineering field operations. In this paper, the constant to be applied in converting between both datum was determined. The constant was found to be 17.79m. The horizontal and vertical accuracy standard was also determined as well as the stack maps.

scholarly journals Accurate and Rapid Broadcast Ephemerides for Beidou-Maneuvered Satellites

2019 ◽  
Vol 11 (7) ◽  
pp. 787 ◽  
Author(s):  
Jing Qiao ◽  
Wu Chen ◽  
Shengyue Ji ◽  
Duojie Weng
Keyword(s):  
Orbit Determination ◽  
Piecewise Linear ◽  
Precise Orbit Determination ◽  
Satellite System ◽  
Navigation Satellite ◽  
Beidou Navigation Satellite System ◽  
German Research ◽  
Global Navigation Satellite ◽  
Ranging Errors

The geostationary earth orbit (GEO) and inclined geosynchronous orbit (IGSO) satellites of the Beidou navigation satellite system are maneuvered frequently. The broadcast ephemeris can be interrupted for several hours after the maneuver. The orbit-only signal-in-space ranging errors (SISREs) of broadcast ephemerides available after the interruption are over two times larger than the errors during normal periods. To shorten the interruption period and improve the ephemeris accuracy, we propose a two-step orbit recovery strategy based on a piecewise linear thrust model. The turning points of the thrust model are firstly determined by comparison of the kinematic orbit with an integrated orbit free from maneuver; afterward, precise orbit determination (POD) is conducted for the maneuvered satellite by estimating satellite orbital and thrust parameters simultaneously. The observations from the IGS Multi-Global Navigation Satellite System (GNSS) Experiment (MGEX) network and ultra-rapid products of the German Research Center for Geosciences (GFZ) are used for orbit determination of maneuvered satellites from Sep to Nov 2017. The results show that for the rapidly recovered ephemerides, the average orbit-only SISREs are 1.15 and 1.0 m 1 h after maneuvering for GEO and IGSO respectively, which is comparable to the accuracy of Beidou broadcast ephemerides in normal cases.

scholarly journals Variability and Performance of Short to Long-Range Single Baseline RTK GNSS Positioning in Indonesia

2019 ◽  
Vol 94 ◽  
pp. 01012 ◽  
Author(s):  
Irwan Gumilar ◽  
Brian Bramanto ◽  
Fuad F. Rahman ◽  
I Made D. A. Hermawan
Keyword(s):  
Long Range ◽  
High Frequency ◽  
Carrier Phase ◽  
Satellite System ◽  
High Accuracy ◽  
Gnss Positioning ◽  
And Performance ◽  
Gnss Network ◽  
Single Baseline ◽  
Global Navigation Satellite

As the modernized Global Navigation Satellite System (GNSS) method, Real Time Kinematic (RTK) ensures high accuracy of position (within several centimeters). This method uses Ultra High Frequency (UHF) radio to transmit the correction data, however, due to gain and power issues, Networked Transport of RTCM via Internet Protocol (RTCM) is used to transmit the correction data for a longer baseline. This Research aims to investigate the performance of short to long-range single baseline RTK GNSS (Up to 80 KM) by applying modified LAMBDA method to resolve the ambiguity in carrier phase. The RTK solution then compared with the differential GNSS network solution. The results indicate that the differences are within RTK accuracy up to 80 km are several centimeter for horizontal solution and three times higher for vertical solution.

scholarly journals Determination of Space Debris Coordinates by Means of a Space Service Vehicle

2016 ◽  
Vol 3 (1) ◽  
pp. 31-37 ◽  
Author(s):  
Vasyl Kondratiuk ◽  
Еduard Kovalevskiy ◽  
Svitlana Ilnytska
Keyword(s):  
Inertial Navigation System ◽  
Space Debris ◽  
Initial Conditions ◽  
Space Vehicle ◽  
Satellite System ◽  
Coordinate Frame ◽  
Space Industry ◽  
Global Character ◽  
Global Navigation Satellite

Abstract The problem of space debris utilization is quite relevant nowadays and has a global character. The space industry experts from all over the world are working on the task of removing space debris. This article proposes the method of determining space debris coordinates by means of the airborne equipment of a space service vehicle. The set of airborne equipment includes a global navigation satellite system receiver, an inertial navigation system and a laser radar. To study the accuracy characteristics of the proposed method under different initial conditions a series of simulations was performed. They showed that the accuracy of determining space debris coordinates becomes higher with the reduction of the distance between the debris and space service vehicle. Stringent requirements for the accuracy of determining the orientation of the coordinate frame of the space vehicle are essential for providing the accuracy characteristics of the method.

scholarly journals Responses to the preparation of strong Kamchatka earth-quakes in the lithosphere–atmosphere–ionosphere system, based on new data from integrated ground and iono-spheric monitoring

2020 ◽  
Vol 196 ◽  
pp. 03005
Author(s):  
Vadim Bogdanov ◽  
Valerey Gavrilov ◽  
Sergey Pulinets ◽  
Dimitar Ouzounov
Keyword(s):  
Earth Quake ◽  
Chemical Potential ◽  
Satellite System ◽  
Daily Monitoring ◽  
Short Term Forecasting ◽  
Total Electronic Content ◽  
Global Navigation Satellite ◽  
Downhole Measurements ◽  
Electronic Content

The experience of short-term forecasting of Kamchatka earthquakes based on complex well measurements at the Petropavlovsk-Kamchatsky geody-namic polygon (PGP) shows that, as a rule, the preparation of strong Kamchatka earthquakes is fairly reliable in the medium-term time scale (months or years be-fore the earthquake). However the determination of the stage beginning imme-diately preceding an earthquake (weeks or days before the main event) is a very difficult task. At present time, the solution of this problem is largely associated with the involvement in the preparation of forecast conclusions of data from continuous monitoring of the ionosphere, carried out by ground-based means of vertical radiosonding and measurements of total electronic content (TEC) using the global navigation satellite system GLONASS and GPS. This is due to the fact that significant changes in a number of ionospheric parameters occur mainly 1-5 days before the Kamchatka earthquakes. The results of the compar-ison of the data of daily monitoring of the ionosphere, including information on TEC, with the data integrated downhole measurements showed a rather high correlation of occurrence of anomalies in the ionosphere before strong earth-quakes with changes in the complex parameters in borehole measurements. As one example, the report presents the results of ionospheric and borehole monitoring obtained in the time neighborhood of the strong (MW = 7.5) the earth-quake that occurred on March 25, 2020 in the area of the Northern Kurils. The results show a high correlation between changes in the specific electrical resis-tivity of the Geospace in the area of the PGP with variations in the TEC and the formation of a number of other anomalies in the ionosphere a few days be-fore the earthquake. These results indicate that it is possible to determine fairly reliably the beginning of the final stage of preparation for a strong earthquake. Currently, methods based on atmospheric parameters monitoring are used quite successfully for predictive estimates of the epicenter and magnitude of an earth-quake: the method of chemical potential corrections for measurements at an altitude of ∼ 100 m, as well as data from measurements of outgoing long-wave infrared radiation (OLR) at the level of the upper edge of clouds (heights of 10 -15 km).

Simulation analysis and performance of a feasible GNSS system with multi-beam antennas deployment operating in Galileo frequency bands

2012 ◽  
Vol 4 (5) ◽  
pp. 537-543
Author(s):  
Constantinos T. Angelis
Keyword(s):  
Simulation Analysis ◽  
European Space Agency ◽  
Satellite System ◽  
Access Time ◽  
Maximum Efficiency ◽  
Satellite Systems ◽  
Space Agency ◽  
Simulation Results ◽  
And Performance ◽  
Global Navigation Satellite

New Global Navigation Satellite System (GNSS) systems under development, such as Galileo, are very promising for future global positioning-based applications. A vast research is undergoing a final stage of implementation in order to fulfill the primary purpose of European Space Agency for developing and then sustaining of 30 (27 + 3 spares) Galileo satellites in orbit. This article presents simulation results for a realistic deployment of multibeam antennas, with a new modified theoretical pattern, in GNSS Satellite Systems. The proposed multibeam antennas use 61-spot beams for maximum efficiency in terms of satellite coverage and accessing high quality of service. In order to prove the reliability and feasibility of this work, various simulations were conducted using the upcoming Galileo system as a platform taking into consideration real-world conditions. Gain analysis versus elevation, Bit Error Rate (BER) and access time simulation results show that the viability of the proposed multibeam antenna deployment is established.

scholarly journals Self-Efficacy, Flow, Affect, Worry and Performance in Elite World Cup Ski Jumping

2018 ◽  
Vol 9 ◽  
Author(s):  
Vegard H. Sklett ◽  
Håvard W. Lorås ◽  
Hermundur Sigmundsson
Keyword(s):  
Self Efficacy ◽  
World Cup ◽  
Ski Jumping ◽  
And Performance

scholarly journals Determination of sea surface height from moving ships with dynamic corrections

2012 ◽  
Vol 2 (3) ◽  
pp. 172-187 ◽  
Author(s):  
J. Reinking ◽  
A. Härting ◽  
L. Bastos
Keyword(s):  
Satellite System ◽  
Ocean Dynamics ◽  
Sea Surface ◽  
Sea Surface Heights ◽  
Positioning Analysis ◽  
Remote Sensing Techniques ◽  
Global Navigation Satellite

AbstractWith the growing global efforts to estimate the influence of civilization on the climate change it would be desirable to survey sea surface heights (SSH) not only by remote sensing techniques like satellite altimetry or (GNSS) Global Navigation Satellite System reflectometry but also by direct and in-situ measurements in the open ocean. In recent years different groups attempted to determine SSH by ship-based GNSS observations. Due to recent advances in kinematic GNSS (PPP) Precise Point Positioning analysis it is already possible to derive GNSS antenna heights with a quality of a few centimeters. Therefore it is foreseeable that this technique will be used more intensively in the future, with obvious advantages in sea positioning. For the determination of actual SSH from GNSS-derived antenna heights aboard seagoing vessels some essential hydrostatic and hydrodynamic corrections must be considered in addition to ocean dynamics and related corrections. Systematic influences of ship dynamics were intensively analyzed and sophisticated techniques were developed at the Jade University during the last decades to precisely estimate mandatory corrections. In this paper we will describe the required analyses and demonstrate their application by presenting a case study from an experiment on a cruise vessel carried out in March 2011 in the Atlantic Ocean.

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