scholarly journals Assessment of EGNOS Tropospheric Correction Model

2001 ◽  
Vol 54 (1) ◽  
pp. 37-55 ◽  
Author(s):  
Nigel Penna ◽  
Alan Dodson ◽  
Wu Chen
Keyword(s):  
Seasonal Variation ◽  
Elevation Angle ◽  
Weather Conditions ◽  
Tropospheric Delay ◽  
Spatially Correlated ◽  
Positioning Errors ◽  
Subsequent Effect ◽  
Weather Changes ◽  
One Year ◽  
Tropospheric Delays

Within the implementation of the European Geo-stationary Navigation Overlay System (EGNOS), a significant residual error in positioning is due to tropospheric delay effects. The EGNOS guidelines recommend that tropospheric delay is modelled using an empirical correction algorithm based on a receiver's height and estimates of meteorological parameters developed from average and seasonal variation data. However, such a simple average and seasonal variation model is unlikely to emulate temporal weather changes exactly. The potential errors involved in the application of the recommended algorithm and the consequent effects on the positioning errors, under typical UK weather conditions, are detailed in this paper. This was achieved by comparing tropospheric delays produced by the EGNOS model, with tropospheric delays estimated from high precision carrier phase GPS, over a one-year period for five UK stations. The RMS EGNOS model zenith tropospheric delay errors ranged from 4·0 to 4·7 cm, with maximum errors ranging from 13·2 to 17·8 cm. The errors were also shown to be spatially correlated. The subsequent effect on position error is shown to be dependent on the satellite elevation cut-off angle adopted and on whether or not the observations are weighted according to the satellite elevation angle.

scholarly journals Integrity Monitoring for Horizontal RTK Positioning: New Weighting Model and Overbounding CDF in Open-Sky and Suburban Scenarios

2020 ◽  
Vol 12 (7) ◽  
pp. 1173 ◽  
Author(s):  
Kan Wang ◽  
Ahmed El-Mowafy ◽  
Chris Rizos ◽  
Jinling Wang
Keyword(s):  
Ambiguity Resolution ◽  
Elevation Angle ◽  
Distribution Functions ◽  
Cumulative Distribution ◽  
Correlated Errors ◽  
Short Baseline ◽  
Integrity Monitoring ◽  
Misleading Information ◽  
Spatially Correlated ◽  
Positioning Errors

Integrity monitoring is an essential task for ensuring the safety of positioning services. Under a selected probability of hazardous misleading information, the protection levels (PLs) are computed according to a considered threat model to bound the positioning errors. A warning message is sent to users when the PL exceeds a pre-set alert limit (AL). In the short-baseline real-time relative kinematic positioning, the spatially correlated errors, such as the the orbital errors and the atmospheric delays are significantly reduced. However, the remaining atmospheric residuals and the multipath that are not considered in the observation model could directly bias the positioning results. In this contribution, these biases are analysed with the focus put on the multipath effects in different measurement environments. A new observation weighting model considering both the elevation angle and the signal-to-noise ratios is developed and their impacts on the positional results are investigated. The coefficients of the proposed weighting model are determined for the open-sky and the suburban scenarios with the positional benefits maximised. Next, the overbounding excess-mass cumulative distribution functions (EMCs) are searched on the between-receiver level for the weighted phase and code observations in these two scenarios. Based on the mean and standard deviations of these EMCs, horizontal protection levels (HPLs) are computed for the ambiguity-fixed solutions of real experiments. The HPLs are compared with the horizontal positioning errors (HPEs) and the horizontal ALs (HALs). Using the sequential exclusion algorithm developed for the ambiguity resolution in this contribution, the full ambiguity resolution can be achieved in around 100% and 95% of the time for the open-sky and the suburban scenarios, respectively. The corresponding HPLs of the ambiguity-fixed solutions are at the sub-dm to dm-level for both scenarios, and all the valid ambiguity-fixed HPLs are below a HAL of 0.5 m. For the suburban scenario with more complicated multipath environments, the HPLs increase by considering extra biases to account for multipath under a certain elevation threshold. In complicated multipath environments, when this elevation threshold is set to 30 degrees, the availability of the ambiguity-fixed solutions could decrease to below 50% for applications requiring HAL as low as 0.1 m.

scholarly journals Estimation of Slant Tropospheric Delays from GNSS Observations with Using Precise Point Positioning Method

2018 ◽  
Vol 25 (1) ◽  
pp. 253-266
Author(s):  
Stepan Savchuk ◽  
Alina Khoptar
Keyword(s):  
Precise Point Positioning ◽  
Elevation Angle ◽  
Global Navigation Satellite Systems ◽  
Tropospheric Delay ◽  
Atmospheric Parameters ◽  
Satellite Systems ◽  
Positioning Method ◽  
Point Positioning ◽  
Tropospheric Delays ◽  
Gnss Observations

AbstractGlobal Navigation Satellite Systems give opportunities for atmospheric parameters analysis in behalf of solving many atmosphere monitoring tasks. The authors of this article demonstrated possibility of slant tropospheric delays determination with using precise point positioning method – PPP. The atmospheric parameters, retrieved from GNSS observations, including zenith tropospheric delays, horizontal gradients, and slant tropospheric delays, are analyzed and evaluated. It was obtained slant tropospheric delays, along the satellite path, for each satellite, at a certain elevation angle and azimuth, at each time, instead of obtaining a single zenith tropospheric delay composed of all visible satellites at one time. The results obtained proved that suggested method was correct.

scholarly journals Plankton studies in a mangrove environment: IV. size fractionation of the phytoplankton

1967 ◽  
Vol 16 (1) ◽  
pp. 39-42 ◽  
Author(s):  
C. Teixeira ◽  
J. Tundisi ◽  
J. Santoro
Keyword(s):  
Seasonal Variation ◽  
Size Range ◽  
Size Fractionation ◽  
Mangrove Swamp ◽  
Mangrove Environment ◽  
Back Ground ◽  
One Year

The seasonal variation of the different fractions of photosynthesizing phytoplankton, measured by C-14 uptake, was studied in a mangrove swamp region, at 25º south latitude. The data showed that the fraction with size range from 5 µ, to 65 µ, was responsible for an average of 61.80% of C-14 uptake of the phytoplankton, during one year, samples having been taken every other month, and showed little seasonal variation when compared with the fraction larger than 65 µ. The results presented here, confirmed general conclusions of other authors, and provided a back-ground for future investigation in the area.

scholarly journals CREATING MULTI-TEMPORAL MAPS OF URBAN ENVIRONMENTS FOR IMPROVED LOCALIZATION OF AUTONOMOUS VEHICLES

2020 ◽  
Vol XLIII-B2-2020 ◽  
pp. 317-323
Author(s):  
J. Schachtschneider ◽  
C. Brenner
Keyword(s):  
Urban Areas ◽  
Autonomous Vehicles ◽  
Weather Conditions ◽  
Point Clouds ◽  
Urban Environments ◽  
Seasonal Effects ◽  
Data Set ◽  
Multi Temporal ◽  
One Year

Abstract. The development of automated and autonomous vehicles requires highly accurate long-term maps of the environment. Urban areas contain a large number of dynamic objects which change over time. Since a permanent observation of the environment is impossible and there will always be a first time visit of an unknown or changed area, a map of an urban environment needs to model such dynamics.In this work, we use LiDAR point clouds from a large long term measurement campaign to investigate temporal changes. The data set was recorded along a 20 km route in Hannover, Germany with a Mobile Mapping System over a period of one year in bi-weekly measurements. The data set covers a variety of different urban objects and areas, weather conditions and seasons. Based on this data set, we show how scene and seasonal effects influence the measurement likelihood, and that multi-temporal maps lead to the best positioning results.

scholarly journals Mapping users' expectations regarding extended-range forecasts

2018 ◽  
Vol 15 ◽  
pp. 99-106 ◽  
Author(s):  
Tiina Ervasti ◽  
Hilppa Gregow ◽  
Andrea Vajda ◽  
Terhi K. Laurila ◽  
Antti Mäkelä
Keyword(s):  
Everyday Life ◽  
Design Process ◽  
General Public ◽  
Online Survey ◽  
Weather Conditions ◽  
The Everyday ◽  
Extended Range ◽  
One Year ◽  
Weather Risks ◽  
Range Forecasts

Abstract. An online survey was used to map the needs and preferences of the Finnish general public concerning extended-range forecasts and their presentation. First analyses of the survey were used to guide the co-design process of novel extended-range forecasts to be developed and tested during the project. In addition, the survey was used to engage the respondents from the general public to participate in a one year piloting phase that started in June 2017. The respondents considered that the tailored extended-range forecasts would be beneficial in planning activities, preparing for the weather risks and scheduling the everyday life. The respondents also perceived the information about the impacts of weather conditions more important than advice on how to prepare for the impacts.

scholarly journals PERFORMANCE ANALYSIS OF DOPPLER AIDED GPS/QZSS PRECISE POSITIONING FOR LAND VEHICLES

2013 ◽  
Vol 20 (1) ◽  
pp. 85-96 ◽  
Author(s):  
Byung-Hyun Lee ◽  
Gyu-In Jee
Keyword(s):  
Urban Area ◽  
Elevation Angle ◽  
Satellite System ◽  
Transport Systems ◽  
Doppler Measurement ◽  
Precise Positioning ◽  
Multipath Error ◽  
Precise Position ◽  
Land Vehicles ◽  
Positioning Errors

ABSTRACT For ITS (Intelligent Transport Systems), especially for land vehicles, precise position is the prime information. GNSS is the most popular navigation system. Generally, ITS demands lane distinguishable positioning accuracy. However urban area is most environments of land vehicles and the signal blocks of satellite with low elevation angle, multipath error and etc. make unreliable positioning results. Especially, lack of number of visible satellites (fewer than 4 satellites) cannot provide positioning results. QZSS (Quasi-Zenith Satellite System) which operated by Japan has high interoperability. In addition, its elevation angle is very high in long time in Korea. It means QZSS signal can be received in urban area and it can be great advantage for land vehicles. The most positioning errors are occurred by multipath, cycle slip, and etc. For example, multipath error is unexpected momentary error. In order to reduce position error, smoothing technique in position domain is needed. In this paper, precise positioning for land vehicles was evaluated. First, by using QZSS, probability of navigation solution was enhanced. Second, the reliability is improved by smoothing positioning result using Doppler measurement. The analysis was performed by trajectory analysis using precise map data.

scholarly journals Correlations between weather parameters, atmospheric hydrogen sulphide level and vitamin B12 administration to H2S exposed workers

2019 ◽  
Vol 70 (1) ◽  
pp. 6-11
Author(s):  
Livia-Cristina Borcan ◽  
Florin Borcan ◽  
Elena-Ana Păuncu ◽  
Mirela Cleopatra Tomescu
Keyword(s):  
Blood Pressure ◽  
Vitamin B12 ◽  
Hydrogen Sulphide ◽  
Prolonged Exposure ◽  
Numerical Data ◽  
Weather Conditions ◽  
Professional Exposure ◽  
Exposed Workers ◽  
Weather Parameters ◽  
One Year

Abstract Hydrogen sulphide, a highly toxic gas, can be used in crenotherapy to balance all metabolic processes (minerals, fats and proteins). The main aims of this study were to correlate the weather characteristics with the atmospheric H2S level and to evaluate the antidote activity of B12 Vitamin in the case of prolonged exposure to this compound. 46 volunteers, people from the medical staff of an important Romanian thermal water spring spa, with professional exposure at H2S, were enrolled in this study; numerical data about their blood pressure, atmospheric H2S concentration and about the weather conditions were collected every month for one year. The results indicate an improvement in the blood pressure of volunteers treated with Vitamin B12; no significant correlation between the concentration of total urinary sulphur and the concentration of atmospheric H2S level was found.

scholarly journals Forecasting and Modelling of Solar Radiation for Photovoltaic (PV) Systems

2021 ◽  
Author(s):  
Ines Sansa ◽  
Najiba Mrabet Bellaaj
Keyword(s):  
Time Series ◽  
Solar Radiation ◽  
Cloud Cover ◽  
Moving Average ◽  
Arma Model ◽  
Weather Conditions ◽  
Pv Systems ◽  
Auto Regressive ◽  
Micro Grid ◽  
One Year

Solar radiation is characterized by its fluctuation because it depends to different factors such as the day hour, the speed wind, the cloud cover and some other weather conditions. Certainly, this fluctuation can affect the PV power production and then its integration on the electrical micro grid. An accurate forecasting of solar radiation is so important to avoid these problems. In this chapter, the solar radiation is treated as time series and it is predicted using the Auto Regressive and Moving Average (ARMA) model. Based on the solar radiation forecasting results, the photovoltaic (PV) power is then forecasted. The choice of ARMA model has been carried out in order to exploit its own strength. This model is characterized by its flexibility and its ability to extract the useful statistical properties, for time series predictions, it is among the most used models. In this work, ARMA model is used to forecast the solar radiation one year in advance considering the weekly radiation averages. Simulation results have proven the effectiveness of ARMA model to forecast the small solar radiation fluctuations.

Comparison of Tropospheric Zenith Wet Delay from VLBI and GNSS Estimations

2021 ◽  
Author(s):  
Vicky Jia Liu ◽  
Maaria Nordman ◽  
Nataliya Zubko
Keyword(s):  
Time Series ◽  
Seasonal Variations ◽  
Elevation Angle ◽  
Correlation Coefficients ◽  
Satellite System ◽  
Tropospheric Delay ◽  
Polar Regions ◽  
Long Baseline ◽  
Zenith Wet Delay ◽  
Space Geodetic Techniques

<p>Tropospheric delay is one of the major error sources for space geodetic techniques such as Very Long Baseline Interferometry (VLBI) and Global Navigation Satellite System (GNSS). In this study, we compared the agreement of tropospheric zenith wet delay (ZWD) seasonal variations derived from VLBI and GNSS observations at 8 stations that are located at all around the globe. We have analysed time series of 8 years, starting in 2012 until end of 2019. Results show that VLBI_ZWD present clear seasonal variations which depend on the location of each station, in the tropics the variability is more pronounced than in mid-latitudes or polar regions. Furthermore, the VLBI_ZWD also shows a reasonably good agreement with seasonal fit model. When comparing zenith wet delays derived from co-located GNSS and VLBI stations at  cut-off elevation angle, they agree quite well, which is proved by the high correlation coefficients, varying from 0.6 up to 0.95. The biases between the techniques are in mm level and standard errors of the whole time series are in few centimetres.</p>

scholarly journals Optimized Single-Axis Schedule Solar Tracker in Different Weather Conditions

Energies ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 5226
Author(s):  
Nurzhigit Kuttybay ◽  
Ahmet Saymbetov ◽  
Saad Mekhilef ◽  
Madiyar Nurgaliyev ◽  
Didar Tukymbekov ◽  
...  
Keyword(s):  
Rotation Angle ◽  
Tracking System ◽  
Weather Conditions ◽  
Main Task ◽  
Solar Panels ◽  
Simple Method ◽  
Solar Tracking ◽  
Rainy Weather ◽  
Solar Tracker ◽  
One Year

Improving the efficiency of solar panels is the main task of solar energy generation. One of the methods is a solar tracking system. One of the most important parameters of tracking systems is a precise orientation to the Sun. In this paper, the performance of single-axis solar trackers based on schedule and light dependent resistor (LDR) photosensors, as well as a stationary photovoltaic installation in various weather conditions, were compared. A comparative analysis of the operation of a manufactured schedule solar tracker and an LDR solar tracker in different weather conditions was performed; in addition, a simple method for determining the rotation angle of a solar tracker based on the encoder was proposed. Finally, the performance of the manufactured solar trackers was calculated, taking into account various weather conditions for one year. The proposed single-axis solar tracker based on schedule showed better results in cloudy and rainy weather conditions. The obtained results can be used for designing solar trackers in areas with a variable climate.

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