scholarly journals A Novel Rapid GNSS Network Solution in Mountainous Region Monitoring considering the Tropospheric Delay at Ground Points

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Guangwei Jiang ◽  
Panlong Wang ◽  
Bin Wang ◽  
Chuanlu Cheng
Keyword(s):  
High Precision ◽  
Elevation Gradient ◽  
Observation Time ◽  
Double Difference ◽  
Tropospheric Delay ◽  
Observation Data ◽  
Positioning Accuracy ◽  
Network Solution ◽  
Mountainous Regions ◽  
Gnss Network

Due to the short peak observation time of global navigation satellite systems (GNSS), the accuracy of the tropospheric delay estimation and the positioning are poor. In this study, a rapid GNSS network solution for mountainous regions is presented. The high-precision tropospheric delay at ground points is obtained from long-term ground observation data and used as a priori constraint in the double-difference equation of short-time synchronous peak observations to realize rapid and high-precision positioning. Chinese mountain survey networks with large elevation gradient (1000~2000 m) were selected for the experimental verification of the proposed method. The results show that the rapid peak positioning method weakened the effect of the residual tropospheric delay caused by the elevation difference, significantly improving the accuracy and reliability of the results. The positioning accuracy of the peak in upward direction was better than 1.1 cm, which meets the requirements of rapid short-span (~1 h) high-precision monitoring and achieves 24 h positioning accuracy. Compared with the traditional solution strategy, the precision of the method with respect to the north (N), east (E), upward (U), and zenith tropospheric delay (ZTD) significantly improved. The accuracy of U improved by more than 47%. Therefore, based on the high accuracy and reliability, information of ground stations can be fully utilized to significantly reduce the peak observation time and the operation costs of surveys in mountain regions.

scholarly journals A Single-Difference Multipath Hemispherical Map for Multipath Mitigation in BDS-2/BDS-3 Short Baseline Positioning

2021 ◽  
Vol 13 (2) ◽  
pp. 304
Author(s):  
Chao Liu ◽  
Yuan Tao ◽  
Haiqiang Xin ◽  
Xingwang Zhao ◽  
Chunyang Liu ◽  
...  
Keyword(s):  
Satellite System ◽  
Observation Time ◽  
Double Difference ◽  
Observation Data ◽  
Multipath Mitigation ◽  
Short Baseline ◽  
Independent Variables ◽  
Positioning Errors ◽  
Single Difference ◽  
Repeat Time

The BeiDou Navigation Satellite System (BDS) features a heterogeneous constellation so that it is difficult to mitigate the multipath in the coordinate-domain. Therefore, mitigating the multipath in the observation-domain becomes more important. Sidereal filtering is commonly used for multipath mitigation, which needs to calculate the orbit repeat time of each satellite. However, that poses a computational challenge and damages the integrity at the end of the multipath model. Therefore, this paper proposes a single-difference model based on the multipath hemispherical map (SD-MHM) to mitigate the BDS-2/BDS-3 multipath in a short baseline. The proposed method is converted from double-difference residuals to single-difference residuals, which is not restricted by the pivot satellite transformation. Moreover, it takes the elevation and the azimuth angles of the satellite as the independent variables of the multipath model. The SD-MHM overcomes the unequal observation time of some satellites and does not require specific hardware. The experimental results show that the SD-MHM reduces the root mean square of the positioning errors by 56.4%, 63.9%, and 67.4% in the east, north, and vertical directions; moreover, it contributes to an increase in the baseline accuracy from 1.97 to 0.84 mm. The proposed SD-MHM has significant advantages in multipath mitigation compared with the advanced sidereal filtering method. Besides, the SD-MHM also features an excellent multipath correction capability for observation data with a period of more than seven days. Therefore, the SD-MHM provides a universal strategy for BDS multipath mitigation.

Friction and Tribological Considerations for Nanometer Range Machining

2001 ◽  
Author(s):  
Som Chattopadhyay
Keyword(s):  
Mathematical Model ◽  
High Precision ◽  
Local Deformation ◽  
Experimental Results ◽  
Precision Machining ◽  
Complex Motion ◽  
Positioning Accuracy ◽  
Nanometer Range ◽  
Motion Characteristic ◽  
Low Speeds

Abstract Positioning accuracy within the range of nanometers is required for high precision machining applications. The implementation of such a range is difficult through the slides because of (a) irregular nature of friction at the slider-guideway interface, and (b) complex motion characteristic at very low speeds. The complexity arises due to the local deformation at the interface prior to breakaway, which is known as microdynamics. In this work prior experimental results exhibiting microdynamics have been appraised, and mathematical model developed to understand this behavior.

scholarly journals Evaluation of the Performance of CFSR Reanalysis Data Set for Estimating Potential Evapotranspiration (PET) in Turkey

2021 ◽  
Author(s):  
AHMET IRVEM ◽  
Mustafa OZBULDU
Keyword(s):  
Potential Evapotranspiration ◽  
Meteorological Data ◽  
Reanalysis Data ◽  
Actual Evapotranspiration ◽  
Observation Data ◽  
Reanalysis Dataset ◽  
Data Set ◽  
Climate Forecast System Reanalysis ◽  
Mountainous Regions ◽  
Weather Stations

Abstract Evapotranspiration is an important parameter for hydrological, meteorological and agricultural studies. However, the calculation of actual evapotranspiration is very challenging and costly. Therefore, Potential Evapotranspiration (PET) is typically calculated using meteorological data to calculate actual evapotranspiration. However, it is very difficult to get complete and accurate data from meteorology stations in, rural and mountainous regions. This study examined the availability of the Climate Forecast System Reanalysis (CFSR) reanalysis data set as an alternative to meteorological observation stations in the computation of potential annual and seasonal evapotranspiration. The PET calculations using the CFSR reanalysis dataset for the period 1987-2017 were compared to data observed at 259 weather stations observed in Turkey. As a result of the assessments, it was determined that the seasons in which the CFSR reanalysis data set had the best prediction performance were the winter (C'= 0.76 and PBias = -3.77) and the autumn (C' = 0.75 and PBias = -12.10). The worst performance was observed for the summer season. The performance of the annual prediction was determined as C'= 0.60 and PBias = -15.27. These findings indicate that the results of the PET calculation using the CFSR reanalysis data set are relatively successful for the study area. However, the data should be evaluated with observation data before being used especially in the summer models.

Experience and results obtained at the ESRF with high-precision air bearing motion systems

2011 ◽  
Vol 1 (MEDSI-6) ◽  
Author(s):  
P. Marion ◽  
L. Ducotte ◽  
M. Nicola ◽  
H. P. van der Kleij ◽  
L. Eybert ◽  
...  
Keyword(s):  
High Precision ◽  
High Accuracy ◽  
Air Bearing ◽  
Air Bearings ◽  
Positioning Accuracy ◽  
Point Of Interest ◽  
Air Film

In high-accuracy motion stages, the positioning accuracy at the point of interest is strongly influenced by guiding errors: for translation motions, straightness errors and angular errors (pitch, yaw and roll); for rotation motions, axial, radial and tilt errors. When air bearings are used for guiding, the air film averages out local irregularities of bearings surfaces, which helps reduce guiding errors considerably. Some results obtained with air bearing precision systems designed and manufactured by specialized companies and tested at ESRF are described below.

scholarly journals Upward shifts in elevation – a winning strategy for mountain viticulture in the context of climate change?

2018 ◽  
Vol 50 ◽  
pp. 02006
Author(s):  
Lukas Egarter Vigl ◽  
Arno Schmid ◽  
Franz Moser ◽  
Andrea Balotti ◽  
Erwin Gartner ◽  
...  
Keyword(s):  
Climate Change ◽  
Winning Strategy ◽  
Elevation Gradient ◽  
Pinot Noir ◽  
Small Scale ◽  
European Alps ◽  
New Production ◽  
Yield Data ◽  
Wine Production ◽  
Mountainous Regions

The advent of global climate change has major impacts upon viticultural production. Changes in the spatial limits of wine production are already being observed around the globe; vineyards are now viable at higher elevations and more polar latitudes. Climatic conditions are also threatening production in existing appellations. Therefore, sound management strategies are vital to maintain high-quality wines and varietal typicity, and to respond to changing market conditions. In mountainous regions such as the European Alps, new production areas at higher elevations are increasingly considered to be a promising solution. However, the suitability of viticulture in general, and even specific varieties of wine grapes, can change drastically across short distances in complex mountain terrain. Variations in temperature and radiation accumulation directly influence plant suitability, yield quantity, and quality. This paper shares initial findings from the REBECKA Project, a transnational research initiative designed to assess the impacts of climate change on mountain viticulture and wine quality in South Tyrol (Italy) and Carinthia (Austria). A three-part approach is utilized to better assess these dynamics: (1) historical crop yield data from local vineyards are assessed, (2) plant phenology stages and polyphenolic compounds of the Pinot Noir variety are analyzed along an elevation gradient and related to bioclimatic indices, and (3) a suitability map is developed that considers small-scale topographic and agro-environmental conditions. Taken together, these components contribute in clarifying many of the opportunities and threats facing high altitude viticulture in a changing world and provide new insights for sound decision-making in alpine vineyards.

scholarly journals A New Asynchronous RTK Method to Mitigate Base Station Observation Outages

Sensors ◽  
2019 ◽  
Vol 19 (15) ◽  
pp. 3376 ◽  
Author(s):  
Yuan Du ◽  
Guanwen Huang ◽  
Qin Zhang ◽  
Yang Gao ◽  
Yuting Gao
Keyword(s):  
Real Time ◽  
Base Station ◽  
Global Navigation Satellite Systems ◽  
Observation Data ◽  
Post Processing ◽  
Positioning Accuracy ◽  
Real Time Processing ◽  
Phase Measurements ◽  
Satellite Systems ◽  
Precise Ephemeris

Real-time kinematic (RTK) positioning is a satellite navigation technique that is widely used to enhance the precision of position data obtained from global navigation satellite systems (GNSS). This technique can reduce or eliminate significant correlation errors via the enhancement of the base station observation data. However, observations received by the base station are often interrupted, delayed, and/or discontinuous, and in the absence of base station observation data the corresponding positioning accuracy of a rover declines rapidly. With the strategies proposed till date, the positioning accuracy can only be maintained at the centimeter-level for a short span of time, no more than three min. To address this, a novel asynchronous RTK method (that addresses asynchronous errors) that can bridge significant gaps in the observations at the base station is proposed. First, satellite clock and orbital errors are eliminated using the products of the final precise ephemeris during post-processing or the ultra-rapid precise ephemeris during real-time processing. Then the tropospheric error is corrected using the Saastamoinen model and the asynchronous ionospheric delay is corrected using the carrier phase measurements from the rover receiver. Finally, a straightforward first-degree polynomial function is used to predict the residual asynchronous error. Experimental results demonstrate that the proposed approach can achieve centimeter-level accuracy for as long as 15 min during interruptions in both real-time and post-processing scenarios, and that the accuracy of the real-time scheme can be maintained for 15 min even when a large systematic error is projected in the U direction.

Hardware Structures for High Precision Pneutronic Systems

2014 ◽  
Vol 658 ◽  
pp. 541-546 ◽  
Author(s):  
Mihai Avram ◽  
Victor Constantin ◽  
Constantin Bucşan ◽  
Daniel Besnea ◽  
Alina Spanu
Keyword(s):  
High Precision ◽  
Weight Ratio ◽  
Nonlinear Behavior ◽  
Compressed Air ◽  
Power Weight ◽  
Precision Positioning ◽  
Positioning Accuracy ◽  
Large Power ◽  
Pneumatic Actuators ◽  
Positioning Systems

Pneutronic systems come with a series of advantages that are natural to working with compressed air, such as the large power/weight ratio of pneumatic actuators, easy and affordable installation and maintenance as well as being clean working systems. However, due to working with compressed air, there are a series of issues, such as static and transient nonlinear behavior, mostly due to the high compressibility of air. Thus, the behavior of such systems is hard to control, especially in terms of precision positioning. The paper deals with proposing three hardware configurations of pneutronic positioning systems in order to assure the imposed positioning accuracy in the presence of disturbances and the preservation in time of the obtained position.

scholarly journals GRQA: Global River Water Quality Archive

2021 ◽  
Author(s):  
Holger Virro ◽  
Giuseppe Amatulli ◽  
Alexander Kmoch ◽  
Longzhu Shen ◽  
Evelyn Uuemaa
Keyword(s):  
Water Quality ◽  
Time Series ◽  
Quality Measurement ◽  
Observation Time ◽  
Quality Analysis ◽  
Quality Data ◽  
Observation Data ◽  
Water Quality Data ◽  
Spatial Coverage ◽  
Global Datasets

Abstract. A major problem related to global water quality analysis and modelling has been the lack of available good quality and consistent water quality measurement datasets with a global spatial coverage. Current study aims to contribute into improving the global datasets on water quality by aggregating and harmonizing five national, continental and global datasets: CESI, GEMSTAT, GLORICH, WATERBASE and WQP. The GRQA compilation involved converting observation data from the five sources into a common format and harmonizing the corresponding metadata, flagging outliers, calculating time series characteristics and detecting duplicate observations from sources with a spatial overlap. The final dataset extends the spatial and temporal coverage of previously available water quality data and contains 42 parameters and over 16 million measurements around the globe covering the 1898–2020 time period. Metadata in the form of statistical tables, maps and figures are provided along with observation time series. The GRQA dataset, supplementary metadata and figures are available for download on the DataCite and OpenAire enabled repository of the University of Tartu, DataDOI, http://dx.doi.org/10.23673/re-273 (Virro et al., 2021).

scholarly journals Development of an End-Toothed Disc-Based Quick-Change Fixture for Ultra-Precision Diamond Cutting

Machines ◽  
2021 ◽  
Vol 9 (11) ◽  
pp. 257
Author(s):  
Xuesen Zhao ◽  
Xiangwu Cui ◽  
Zhenjiang Hu ◽  
Qiang Zhang ◽  
Tao Sun
Keyword(s):  
Finite Element ◽  
High Precision ◽  
High Efficiency ◽  
Small Diameter ◽  
Diamond Turning ◽  
Depth Of Cut ◽  
Diamond Cutting ◽  
Positioning Accuracy ◽  
Small Depth ◽  
Ultra Precision

With its standardized and unified interface, the quick-change fixture is an important part for maintaining high efficiency without compensation of precision in the metal-turning process because it can conveniently realize high-precision repeated clamping and multi-station conversion without complex positioning and adjustment steps. However, the existing quick-change fixture products and related research cannot fully meet the needs of repeatability and applicability raised from ultra-precision, single-point diamond turning with ultra-high accuracy and ultra-small depth of cut. In this paper, we develop a quick-change fixture for ultra-precision diamond turning, in which the end-toothed disc acts as the positioning element. Specifically, the main parameters of two key components of the end-toothed disc and slotted disc spring are calculated analytically to ensure the positioning accuracy of the designed fixture used in the rotation condition, which is further ensured by controlling the machining tolerance of the tooth profile of the end-toothed disc. Additionally, finite element simulations are performed to investigate the static and modal states of the quick-change fixture, which demonstrate a maximum deformation of about 0.9 μm and a minimum natural frequency of 5655.9 Hz for the designed fixture. Two high-precision sensors are used to detect the radial jump and end run-out values after repeated clamping actions, which are employed to verify the repetitive positioning accuracy of the fixture. Subsequent finite-element simulation of the clamping of small-diameter copper bar, as well as the diamond turning experiment, jointly demonstrate that the designed fixture can achieve a precision of 1 μm. Current work provides an effective quick-change fixture to reduce the deformation of a weak-stiffness workpiece caused by clamping deformation in ultra-precision diamond cutting.

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