scholarly journals Validating HY-2A CMR Precipitable Water Vapor Using Ground-based and Shipborne GNSS Observations

2020 ◽  
Author(s):  
Zhilu Wu ◽  
Yanxiong Liu ◽  
Yang Liu ◽  
Jungang Wang ◽  
Xiufeng He ◽  
...  
Keyword(s):  
Water Vapor ◽  
Microwave Radiometer ◽  
Precipitable Water ◽  
Global Navigation Satellite Systems ◽  
High Temporal Resolution ◽  
Satellite Systems ◽  
The Indian Ocean ◽  
Global Navigation Satellite ◽  
Gnss Data ◽  
Gnss Observations

Abstract. The calibration microwave radiometer (CMR) onboard Haiyang-2A satellite provides wet tropospheric delays correction for altimetry data, which can also contribute to the understanding of climate system and weather processes. Ground-based Global Navigation Satellite Systems (GNSS) provide precise PWV with high temporal resolution and could be used for calibration and monitoring of the CMR data, and shipborne GNSS provides accurate PWV over open oceans, which can be directly compared with uncontaminated CMR data. In this study, the HY-2A CMR water vapor product is validated using ground-based GNSS observations of 100 IGS stations along the coastline and 56-day shipborne GNSS observations over the Indian Ocean. The processing strategy for GNSS data and CMR data is discussed in detail. Special efforts were made to the quality control and reconstruction of contaminated CMR data. The validation result shows that HY-2A CMR PWV agrees well with ground-based GNSS PWV with 2.67 mm in RMS within 100 km. Geographically, the RMS is 1.12 mm in the polar region and 2.78 mm elsewhere. The PWV agreement between HY-2A and shipborne GNSS shows a significant correlation with the distance between the ship and the satellite footprint, with an RMS of 1.57 mm for the distance threshold of 100 km. Ground-based GNSS and shipborne GNSS agree with HY-2A CMR well with no obvious system error.

scholarly journals Validating HY-2A CMR precipitable water vapor using ground-based and shipborne GNSS observations

2020 ◽  
Vol 13 (9) ◽  
pp. 4963-4972
Author(s):  
Zhilu Wu ◽  
Yanxiong Liu ◽  
Yang Liu ◽  
Jungang Wang ◽  
Xiufeng He ◽  
...  
Keyword(s):  
Water Vapor ◽  
Microwave Radiometer ◽  
Precipitable Water ◽  
Satellite System ◽  
Precipitable Water Vapor ◽  
Tropospheric Delay ◽  
High Temporal Resolution ◽  
International Gnss Service ◽  
Global Navigation Satellite ◽  
Gnss Observations

Abstract. The calibration microwave radiometer (CMR) on board the Haiyang-2A (HY-2A) satellite provides wet tropospheric delay correction for altimetry data, which can also contribute to the understanding of climate system and weather processes. The ground-based global navigation satellite system (GNSS) provides precise precipitable water vapor (PWV) with high temporal resolution and could be used for calibration and monitoring of the CMR data, and shipborne GNSS provides accurate PWV over open oceans, which can be directly compared with uncontaminated CMR data. In this study, the HY-2A CMR water vapor product is validated using ground-based GNSS observations of 100 International GNSS Service (IGS) stations along the global coastline and 56 d shipborne GNSS observations over the Indian Ocean. The processing strategy for GNSS data and CMR data is discussed in detail. Special efforts were made in the quality control and reconstruction of contaminated CMR data. The validation result shows that HY-2A CMR PWV agrees well with ground-based GNSS PWV with 2.67 mm as the root mean square (rms) within 100 km. Geographically, the rms is 1.12 mm in the polar region and 2.78 mm elsewhere. The PWV agreement between HY-2A and shipborne GNSS shows a significant correlation with the distance between the ship and the satellite footprint, with an rms of 1.57 mm for the distance threshold of 100 km. Ground-based GNSS and shipborne GNSS agree with HY-2A CMR well.

On the determination of weighted mean temperature in Indonesia

2021 ◽  
Author(s):  
Nabila Putri ◽  
Johannes Boehm ◽  
Dudy D. Wijaya ◽  
Wedyanto Kuntjoro ◽  
Zamzam Tanuwijaya ◽  
...  
Keyword(s):  
Water Vapor ◽  
Surface Temperature ◽  
Water Vapor Pressure ◽  
Precipitable Water ◽  
Global Navigation Satellite Systems ◽  
Satellite Systems ◽  
Mean Temperature ◽  
Weather Model ◽  
Weighted Mean Temperature ◽  
Global Navigation Satellite

<p>The mean temperature weighted with water vapor pressure (Tm) is an important parameter to obtain precipitable water vapor (PWV) from the Global Navigation Satellite Systems (GNSS) observations. This study investigates the possible impacts of equatorial troposphere on Tm estimates and its relation with surface temperature Ts. We calculated Tm in Indonesia from a Numerical Weather Model at nine InaCORS sites. We used 3-hourly ERA5 pressure, temperature, and humidity profiles for the year 2019. We found that Tm and surface temperature Ts in Indonesia have low correlation, less than 0.4. Seasonal and site-specific Tm-Ts relationships have slightly higher correlation, although the values can vary significantly. The highest correlation of around 0.7 is found at site CPUT in Kalimantan. We calculated Tm at nine additional stations in Kalimantan and found that stations located farther from the coast tend to have higher correlation, independent of the seasons. This suggests that Tm is also influenced by the vicinity to the coast. Based on our findings, the use of a general Tm-Ts relationship in Indonesia may not be appropriate. Further studies are necessary to develop an improved Tm over Indonesian region.</p>

scholarly journals 50 anos de sinergia entre Geodésia Espacial e Meteorologia: do erro no posicionamento GNSS a aplicações de previsão de precipitação de curtíssimo prazo

2020 ◽  
Vol 72 ◽  
pp. 1509-1535
Author(s):  
Tayná Aparecida Ferreira Gouveia ◽  
João Francisco Galera Monico ◽  
Daniele Barroca Marra Alves ◽  
Luiz Fernando Sapucci ◽  
Felipe Geremia Nievinski
Keyword(s):  
Water Vapor ◽  
Precipitable Water ◽  
Precipitable Water Vapor ◽  
Global Navigation Satellite Systems ◽  
Navigation Satellite ◽  
Satellite Systems ◽  
Global Navigation ◽  
Global Navigation Satellite

A atmosfera neutra (ou troposfera) causa refração nos sinais de radiofrequência, que resulta em erros nas medidas do Global Navigation Satellite Systems (GNSS) empregadas no posicionamento geodésico. Já para a Meteorologia esse efeito pode representar medidas importantes da concentração dos constituintes atmosféricos, principalmente em regiões onde não se pode realizar sondagem atmosférica convencional, por meio de radiossondas acopladas a balões. Duas técnicas GNSS podem ser empregadas para isso. A primeira utiliza receptores em estações terrestres que fornecem estimativas do conteúdo integrado verticalmente de umidade na atmosfera neutra (Precipitable Water Vapor - PWV). A segunda, com receptores localizados em plataformas espaciais, com os quais obtém perfis atmosféricos de pressão, temperatura e umidade, na técnica conhecida como Rádio-ocultação GNSS. Essas medidas têm um potencial significativo para aplicações em previsões de curtíssimo prazo (30 minutos) de eventos extremos de precipitação (>35 mm). O objetivo principal deste artigo é realizar uma revisão do estado da arte da sinergia entre a Geodésia e a Meteorologia na modelagem da atmosfera neutra (neutrosfera), seu efeito no posicionamento GNSS e na estimativa dos constituintes atmosféricos e suas aplicações. Além disso, apresenta os aprimoramentos e novos desafios desenvolvidos na modelagem do atraso para o posicionamento de alta acurácia.

scholarly journals Decadal variations in atmospheric water vapor time series estimated using ground-based GNSS

2016 ◽  
Author(s):  
Fadwa Alshawaf ◽  
Galina Dick ◽  
Stefan Heise ◽  
Tzvetan Simeonov ◽  
Sibylle Vey ◽  
...  
Keyword(s):  
Time Series ◽  
Water Vapor ◽  
Linear Trend ◽  
Precipitable Water ◽  
The Other ◽  
Global Navigation Satellite Systems ◽  
Positive Trend ◽  
Satellite Systems ◽  
Decadal Variations ◽  
Global Navigation Satellite

Abstract. Ground-based GNSS (Global Navigation Satellite Systems) have efficiently been used since the 1990s as a meteorological observing system. Recently scientists used GNSS time series of precipitable water vapor (PWV) for climate research. In this work, we use time series from GNSS, European Center for Medium-Range Weather Forecasts Reanalysis (ERA-Interim) data, and meteorological measurements to evaluate climate evolution in Central Europe. The assessment of climate change requires monitoring of different atmospheric variables such as temperature, PWV, precipitation, and snow cover. PWV time series were obtained by three methods: 1) estimated from ground-based GNSS observations using the method of precise point positioning, 2) inferred from ERA-Interim data, and 3) determined based on daily surface measurements of temperature and relative humidity. The other variables are available from surface meteorological stations or received from ERA-Interim. The PWV trend component estimated from GNSS data strongly correlates with that estimated from the other data sets. The linear trend is estimated by straight line fitting over 30 years of seasonally-adjusted PWV time series obtained using meteorological measurements. The results show a positive trend in the PWV time series at more than 60 GNSS sites with an increase of 0.3–0.6 mm/decade. In this paper, we compare the results of three stations. The temporal increment of the PWV correlates with the temporal increase in the temperature levels.

scholarly journals Assessment of the Cutting Performance of a Robot Mower Using Custom Built Software

Agronomy ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 230 ◽  
Author(s):  
Luisa Martelloni ◽  
Marco Fontanelli ◽  
Stefano Pieri ◽  
Christian Frasconi ◽  
Lisa Caturegli ◽  
...  
Keyword(s):  
Autonomous Vehicles ◽  
Global Navigation Satellite Systems ◽  
Forward Speed ◽  
Satellite Systems ◽  
Different Shapes ◽  
Global Navigation Satellite ◽  
High Level ◽  
Short Time ◽  
Gnss Data ◽  
Collection And Management

Before the introduction of positioning technologies in agriculture practices such as global navigation satellite systems (GNSS), data collection and management were time-consuming and labor-intensive tasks. Today, due to the introduction of advanced technologies, precise information on the performance of agricultural machines, and smaller autonomous vehicles such as robot mowers, can be collected in a relatively short time. The aim of this work was to track the performance of a robot mower in various turfgrass areas of an equal number of square meters but with four different shapes by using real-time kinematic (RTK)-GNSS devices, and to easily extract data by a custom built software capable of calculating the distance travelled by the robot mower, the forward speed, the cutting area, and the number of intersections of the trajectories. These data were then analyzed in order to provide useful functioning information for manufacturers, entrepreneurs, and practitioners. The path planning of the robot mower was random and the turfgrass area for each of the four shapes was 135 m2 without obstacles. The distance travelled by the robot mower, the mean forward speed, and the intersections of the trajectories were affected by the interaction between the time of cutting and the shape of the turfgrass. For all the different shapes, the whole turfgrass area was completely cut after two hours of mowing. The cutting efficiency decreased by increasing the time, as a consequence of the increase in overlaps. After 75 minutes of cutting, the efficiency was about 35% in all the turfgrass areas shapes, thus indicating a high level of overlapping.

scholarly journals Experimental estimation of GNSS performances at the national aviation university

2020 ◽  
Vol 164 ◽  
pp. 03052
Author(s):  
Volodymir Kharchenko ◽  
Valeriy Konin ◽  
Olexiy Pogurelsky ◽  
Ekaterina Stativa
Keyword(s):  
Experimental Data ◽  
Continuous Monitoring ◽  
Goal Achievement ◽  
Global Navigation Satellite Systems ◽  
Reference Station ◽  
Satellite Systems ◽  
Systems Quality ◽  
Primary Focus ◽  
Global Navigation Satellite ◽  
Gnss Data

The goal of the research is to develop a of Global Navigation Satellite Systems quality monitoring methodology based on available equipment in the satellite navigation laboratory of the National Aviation University (Kyiv, Ukraine). For successful the goal achievement it is necessary to solve follow list of tasks: to determine the composition of the necessary equipment and order of it installing and connection; to develop the necessary software for processing received GNSS data; to estimate the GNSS characteristics with the help of experimental data. The primary focus of this research is on the following characteristics: accuracy (in terms of deviation coordinates in horizontal and vertical planes from the coordinates of the reference station and numerical values in meters); integrity information (summarized in the form of horizontal and Stanford plots); overall availability of service – measured as the availability of signals meeting the requirements for instrumented approaches with vertical guidance (APV) APV-1, APV-2, and Category 1 (CAT-1) precision approaches to runways. The main result of this research is developing software that could be applied for continuous monitoring of GNSS performances. The possibilities of it were successfully tested with the help of experimental data received from GPS and Galileo satellites.

scholarly journals Towards FAIR GNSS data: challenges and open problems

2020 ◽  
Author(s):  
Anna Miglio ◽  
Carine Bruyninx ◽  
Andras Fabian ◽  
Juliette Legrand ◽  
Eric Pottiaux ◽  
...  
Keyword(s):  
Research Policy ◽  
Global Navigation Satellite Systems ◽  
International Gnss Service ◽  
Open Problems ◽  
Data Repositories ◽  
Satellite Systems ◽  
Data Practices ◽  
Metadata Standards ◽  
Global Navigation Satellite ◽  
Gnss Data

<p>Nowadays, we measure positions on Earth’s surface thanks to Global Navigation Satellite Systems (GNSS) e.g. GPS, GLONASS, and Galileo. Activities such as navigation, mapping, and surveying rely on permanent GNSS tracking stations located all over the world.<br>The Royal Observatory of Belgium (ROB) maintains and operates a repository containing data from hundreds of GNSS stations belonging to the European GNSS networks (e.g. EUREF, Bruyninx et al., 2019). </p><p>ROB’s repository contains GNSS data that are openly available and rigorously curated. The curation data include detailed GNSS station descriptions (e.g. location, pictures, and data author) as well as quality indicators of the GNSS observations.</p><p>However, funders and research policy makers are progressively asking for data to be made <em>Findable, Accessible, Interoperable, and Reusable (FAIR)</em> and therefore to increase data transparency, discoverability, interoperability, and accessibility.</p><p>In particular, within the GNSS community, there is no shared agreement yet on the need for making data <em>FAIR</em>. Therefore, turning GNSS data <em>FAIR</em> presents many challenges and, although <em>FAIR</em> data has been included in EUREF’s strategic plan, no practical roadmap has been implemented so far. We will illustrate the specific difficulties and the need for an open discussion including also other communities working on <em>FAIR</em> data.</p><p>For example, making GNSS data easily <em>findable</em> and <em>accessibl</em>e would require to attribute persistent identifiers to the data. It is worth noting that the International GNSS Service (IGS) is only now beginning to consider the attribution of DOIs (Digital Object Identifiers) to GNSS data, mainly to allow data citation and acknowledgement of data providers. Some individual GNSS data repositories are using DOIs (such as UNAVCO, USA).  Are DOIs the only available option or are there more suitable types of URIs (Uniform Resource Identifiers) to consider?</p><p>The GNSS community would greatly benefit from <em>FAIR</em> data practices, as at present, (almost) no licenses have been attributed to GNSS data, data duplication is still an issue, historical provenance information is not available because of data manipulations in data centres, citation of the data providers is far from the rule, etc.</p><p>To move further along the path towards <em>FAIR</em> GNSS data, one would need to implement standardised metadata models to ensure data <em>interoperability</em>, but, as several metadata standards are already in use in various scientific disciplines, which one to choose?</p><p>Then, to facilitate the <em>reuse</em> (and long-term preservation) of GNSS data, all metadata should be properly linked to the corresponding data and additional metadata, such as provenance and license information. The latter is a good example up for discussion: despite the fact that ‘CC BY’ license is already assigned to some of the GNSS data, other licenses might need to be enabled.</p><p> </p><p>Bruyninx C., Legrand J., Fabian A., Pottiaux E. (2019) “GNSS Metadata and Data Validation in the EUREF Permanent Network”. GPS Sol., 23(4), https://doi: 10.1007/s10291-019-0880-9           </p>

scholarly journals Estimating trends in atmospheric water vapor and temperature time series over Germany

2017 ◽  
Author(s):  
Fadwa Alshawaf ◽  
Kyriakos Balidakis ◽  
Galina Dick ◽  
Stefan Heise ◽  
Jens Wickert
Keyword(s):  
Time Series ◽  
Water Vapor ◽  
Temporal Trends ◽  
Precipitable Water ◽  
Reanalysis Data ◽  
Global Navigation Satellite Systems ◽  
Satellite Systems ◽  
Surface Measurements ◽  
Standard Deviations ◽  
Gnss Time Series

Abstract. Ground-based GNSS (Global Navigation Satellite Systems) have efficiently been used since the 1990s as a meteorological observing system. Recently scientists used GNSS time series of precipitable water vapor (PWV) for climate research. In this work, we compare the temporal trends estimated from GNSS time series with those estimated from European Center for Medium-Range Weather Forecasts Reanalysis (ERA-Interim) data and meteorological measurements. We aim at evaluating climate evolution in Germany by monitoring different atmospheric variables such as temperature and PWV. PWV time series were obtained by three methods: 1) estimated from ground-based GNSS observations using the method of precise point positioning, 2) inferred from ERA-Interim reanalysis data, and 3) determined based on daily in situ measurements of temperature and relative humidity. The other relevant atmospheric parameters are available from surface measurements of meteorological stations or derived from ERA-Interim. The trends are estimated using two methods, the first applies least squares to seasonally-adjusted time series and the second using the Theil-Sen estimator. The trends estimated at 113 GNSS sites, with 10 and 19 year temporal coverage, varies between −1.5 and 2 mm/decade with standard deviations below 0.25 mm/decade. These values depend on the length and the variations of the time series. Therefore, we estimated the PWV trends using ERA-Interim and surface measurements spanning from 1991 to 2016 (26 years) at synoptic 227 stations over Germany. The former shows positive PWV trends below 0.5 mm/decade while the latter shows positive trends below 0.9 mm/decade with standard deviations below 0.03 mm/decade. The estimated PWV trends correlate with the temperature trends.

scholarly journals Determining the guidance system accuracy with the support of a large GNSS dataset

2013 ◽  
Vol 59 (Special Issue) ◽  
pp. S65-S70 ◽  
Author(s):  
V. Rataj ◽  
J. Galambošová ◽  
M. Vašek
Keyword(s):  
Monitoring System ◽  
Global Navigation Satellite Systems ◽  
Guidance System ◽  
Rectangular Coordinate System ◽  
Projection System ◽  
Satellite Systems ◽  
Ideal Line ◽  
Guidance Systems ◽  
Global Navigation Satellite ◽  
Gnss Data

Several methods are used presently to assess the accuracy of machinery guidance systems. However, these offer a limited number of records and are time and cost consuming. As the machinery is often equipped with a monitoring system for the management purposes, these data can be used. The aim of this work was to develop and verify a method to determine the accuracy of the machinery guidance systems based on a large dataset obtained from the machinery monitoring system. The proposed method uses the transformation of global navigation satellite systems (GNSS) data into a rectangular coordinate system SJTSK (National projection system – Krovak projection). Based on the geometry principle, the ideal line can be determined, and afterwards, the off-track error of each actual position can be calculated. After the verification of this method, it can be concluded that it brings benefits in terms of further use of the data from the monitoring systems, the estimation of the error based on a robust dataset, elimination of subjective and measurement method errors, as well as spatial localisation of the off-track errors at the field.

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