检索结果-南通市图书馆

Sensitivity analysis of parameters and contrasting performance of ground filtering algorithms with UAV photogrammetry-based and LiDAR point clouds

在线全文

学校读者我要写书评

暂无评论

International Journal of Digital Earth 2020年第12期13卷 1672-1694页

作者： Petr Klápště Michal Fogl Vojtěch Barták Kateřina Gdulová Rudolf Urban Vítězslav Moudrý department of Applied Geoinformatics and Spatial Planning Faculty of Environmental SciencesCzech University of Life Sciences PragueKamýcká129Praha-Suchdol16500Czech Republic Department of Special Geodesy Faculty of Civil EngineeringCzech Technical University in PraguePragueCzech Republic

Most ground filtering algorithms are primarily designed for airborne LiDAR point cloud processing and their successful use in identifying ground points from photogrammetric point clouds remains questionable.We compared six ground filtering algorithms implemented in Metashape,ArcGIS,CloudCompare,LAStools,and PDAL.We used UAV photogrammetry-based(acquired under leaf-off conditions)and airborne LiDAR(leaf-on)point clouds of the same area to:(i)compare accuracy of generated DTMs;(ii)evaluate the effect of vegetation density and terrain slope on filtering accuracy;and(iii)assess which algorithm parameters have the greatest effect on the filtering accuracy.Our results show that the performance of filtering algorithms was affected by the point cloud type,terrain slope and vegetation cover.The results were generally better for LiDAR(RMSE 0.13–0.19 m)than for photogrammetric(RMSE 0.19–0.23 m)point clouds.The behavior in varying vegetation and terrain conditions was consistent for LiDAR point clouds.However,when applied on photogrammetric point clouds,the algorithms’behavior was inconsistent,especially in areas of steep slope(except for the Progressive Triangulated Irregular Network in LAStools).Parameters related to the selection of the initial minimum elevation ground points were the most influential in all algorithms and point clouds.

关键词： DTM filtering LiDAR point cloud spoil heap UAV

Precise orbit determination for LEO satellites:single-receiver ambiguity resolution using GREAT products

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Geo-Spatial Information Science 2022年第1期25卷 63-73页

作者： Xingxing Li Yujie Qin Keke Zhang Jiaqi Wu Wei Zhang Qian Zhang Hongmin Zhang School of geodesy and Geomatics Wuhan UniversityWuhanHubeiChina department of geodesy and Remote Sensing of the German Research Centre for Geosciences(GFZ) PotsdamGermany

In recent years,the large Low Earth Orbit(LEO)constellations have become a hot topic due to their great potential to improve the Global Navigation Satellite Systems(GNSS)positioning performance.One of the important focus is how to obtain the accurate and reliable orbits for these constellations with dozens of LEO satellites.The GNSS-based Precise Orbit Determination(POD)will be exclusively performed to achieve this goal,where the Integer Ambiguity Resolution(IAR)plays a key role in acquiring high-quality orbits.In this study,we present a comprehensive analysis of the benefit of the single-receiver IAR in LEO POD and discuss its implication for the future LEO constellations.We perform ambiguity-fixed LEO POD for four typical missions,including Gravity Recovery and Climate Experiment(GRACE)Follow-On(GRACE-FO),Swarm,Jason-3 and Sentinel-3,using the Uncalibrated Phase Delay(UPD)products generated by our GREAT(GNSS+REsearch,Application and Teaching)software.The results show that the ambiguity fixing processing can significantly improve the accuracy of LEO orbits.There are negligible differences between our UPD-based ambiguity-fixed orbits and those based on the Observable Signal Bias(OSB)and Integer Recovery Clock(IRC)products,indicating the good-quality of UPD products we generated.Compared to the float solution,the fixed solution presents a better consistency with the external precise science orbits and the largest accuracy improvement of 5 mm is achieved for GRACE-FO satellites.Meanwhile,the benefit can be observed in laser ranging residuals as well,with a Standard Deviation(STD)reduction of 3–4 mm on average for the fixed solutions.Apart from the absolute orbits,the relative accuracy of the space baseline is also improved by 20–30%in the fixed solutions.The result demonstrates the superior performance of the ambiguity-fixed LEO POD,which appears as a particularly promising technique for POD of future LEO constellations.

关键词： Precise orbit determination single-receiver ambiguity resolution onboard GPS observation LEO

The dual choice of geodetic horizontal reference systems for Ukraine

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

geodesy and Geodynamics 2023年第3期14卷 254-264页

作者： Elena Novikova Alena Palamar Rostyslav Lopunov department of geodesy State Higher Educational InstitutionKryvyi Rih National UniversityKryvyi RihUkraine

Almost all European countries use at least two horizontal reference systems, which allow them to minimize all risks when changing the coordinate system. The first system is used for the needs of the national survey in general, and also for technical applications in engineering surveys. A brief description of this system can be written by the formula: Geocentric Ellipsoid(GRS80) + Projection(UTM). More than half of the European countries for the second national systems use the GRS80 geocentric ellipsoid together with a projection other than UTM, some of them continue to use the projection of the old coordinate systems. The rest of the countries, excluding Ukraine, adapted the existing national coordinate systems to modern requirements, removing deformations from them concerning the ETRS89. A small number of European countries have implemented the GRS80 geocentric ellipsoid together with the UTM projection for cadastral surveys and topographic maps with a scale of 1:5000 and larger. Only one country, Ukraine, chose a variant for the new coordinate system(UCS2000), which is briefly written by the formula: Old Not Geocentric Ellipsoid + New Projection. The analysis of modern coordinate systems of Europe made it possible to formulate two variants of the future coordinate system of Ukraine based on a geocentric ellipsoid. It is shown that the transition to a geocentric ellipsoid will change the coordinates and heights of the points, but practically will not change the distance between the points and the area of the parcels.

关键词： UTM GRS80 Projection parameters Quantitative characteristics of land parcels UCS2000

Template-based smoothing functions for data smoothing in geodesy

在线全文

学校读者我要写书评

暂无评论

geodesy and Geodynamics 2020年第4期11卷 300-306页

作者： M.Kiani department of geodesy University of TehranTehranIran

This paper is aimed at the derivation of a discrete data smoothing function for the discrete Dirichlet condition in a regular grid on the surface of a spheroid.The method employed here is the local L^2-seminorm minimization,through Euler-Lagrange method,for the Beltrami operator.The method results in a weighted average of the surrounding points in a te mplate based on the first order Taylor expansion of the unknown function under consideration.The coefficients of the weighted average are calculated and used to smooth the Geoid height data in Iran,derived from the EGM2008 geopotential model.

关键词： Minimization problem Regular grid Linear composition Beltrami operator Smoothing function

Gaussian Radial Basis Function interpolation in vertical deformation analysis

在线全文

学校读者我要写书评

暂无评论

geodesy and Geodynamics 2021年第3期12卷 218-228页

作者： Mohammad Amin Khalili Behzad Voosoghi department of geodesy Faculty of Geodesy and Geomatics EngineeringK.N.Toosi University of TechnologyTehran 19697-64499Iran

In many deformation analyses,the partial derivatives at the interpolated scattered data points are required.In this paper,the Gaussian Radial Basis Functions(GRBF)is proposed for the interpolation and differentiation of the scattered data in the vertical deformation analysis.For the optimal selection of the shape parameter,which is crucial in the GRBF interpolation,two methods are used:the Power Gaussian Radial Basis Functions(PGRBF)and Leave One Out Cross Validation(LOOCV)(LGRBF).We compared the PGRBF and LGRBF to the traditional interpolation methods such as the Finite Element Method(FEM),polynomials,Moving Least Squares(MLS),and the usual GRBF in both the simulated and actual Interferometric Synthetic Aperture Radar(InSAR)data.The estimated results showed that the surface interpolation accuracy was greatly improved by LGRBF and PGRBF methods in comparison withFEM,polynomial,and MLS methods.Finally,LGRBF and PGRBF interpolation methods are used to compute invariant vertical deformation parameters,i.e.,changes in Gaussian and mean Curvatures in the Groningen area in the North of Netherlands.

关键词： Interpolation accuracy Gaussian Radial Basis Functions Finite Element Method InSAR Vertical deformation

Modeling neutral-atmospheric electromagnetic delays in a“big data”world

在线全文

学校读者我要写书评

暂无评论

Geo-Spatial Information Science 2018年第2期21卷 75-79页

作者： Marcelo C.Santos Thalia Nikolaidou department of geodesy and Geomatics Engineering University of New BrunswickFrederictonCanada

If left unmodeled,the delay suffered by electromagnetic waves while crossing the neutral atmosphere negatively affects Global Navigation Satellite System positioning.The modeling of the delay has been carried out by means of empirical models formulated based on climatological information or using information extracted from numerical weather prediction(NWP)models.This paper explores the potential use of meteorological information of several types that will become available with the increasing number of sensors(e.g.a cell phone,or the thermometer of a nearby smart home)in cyberspace.How can we make use of these potentially huge datasets,which may help to provide the best possible representation of the neutral atmosphere at any given time,as readily and as accurately as possible?This situation falls in the realm of Big Data.A few potential scenarios,a sequential improvement of Marini mapping function coefficients,a self-feeding NWP,and near real-time empirical model updates,are discussed in this paper.The pros and cons of each approach are discussed in comparison with what is done today.Experiments indicate that they have potential for a positive contribution.

关键词： Global navigation satellite system(GNSS) big data neutral atmosphere

Analysis of the displacements of pipeline overpasses based on geodetic monitoring results

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

geodesy and Geodynamics 2022年第1期13卷 50-71页

作者： Roman Shults Andriy Annenkov Gulnur Seitkazina Saule Soltabayeva Zhenis Kozhayev Andrii Khailak Kira Nikitenko Bohdan Sossa Nataliia Kulichenko department of Civil and Environmental Engineering Michigan Technological University Houghton49931 MIUSA department of Applied geodesy Kyiv National University of Construction and Architecture03037 KyivUkraine department of Mining and geodesy K.Turysov Institute of GeologyOil and MiningSatbayev UniversityAlmatyKazakhstan

There are many approaches to address geospatial monitoring of pipeline overpasses,among which the most widespread methods are terrestrial laser scanning and total station measurements.However,there is a problem in comparing the geospatial monitoring data collected by different methods in different epochs.The main task of this work is to find the correspondence between points in different epochs.The total station measurements are carried out in specific discrete points of the pipeline overpass.In contrast,terrestrial laser scanning allows the collection of the whole data set without fixing specific point co-ordinates.In order to compare different data in different epochs,it is necessary to select a relevant presentation of the monitoring results(reference model)and specify appropriate criteria for quality inspection.In general,a pipeline can be presented as a spatial curve.In this study,two types of reference models are considered:cubic splines and Bezier curves.These models are examined for the monitoring of two gas pipeline overpasses.The first measurement epoch is accomplished by the terrestrial laser scanning,and the second measurement epoch is completed by the total station.The reference models are simulated by Matlab coding.The preliminary accuracy of ground laser scanning and total station mea-surement is selected as the criterion of quality inspection.The simulation and comparison results provide the evidence that the correct selection of reference model is a crucial component of successful geospatial monitoring.The results show that the Hermite splines are effective in the comparison of different data sets.These splines present the interpolation accuracy compatible with measurement accuracy,i.e.,15-20 mm for spatial displacement determination.

关键词： Geospatial monitoring Terrestrial laser scanning Total station Pipeline

Interactions between hotspots and the Southwest Indian Ridge during the last 90 Ma:Implications on the formation of oceanic plateaus and intra-plate seamounts

在线全文

学校读者我要写书评

暂无评论

Science China Earth Sciences 2011年第8期54卷 1177-1188页

作者： ZHANG Tao 1,2,3,4,LIN Jian 5 & GAO JinYao 3,4 1 Institute of geodesy and Geophysics,Chinese Academy of Sciences,Wuhan 430077,China 2 Graduate University of Chinese Academy of Sciences,Beijing 100049,China 3 The Second Institute of Oceanography,State Oceanic Administrator,Hangzhou 310012,China 4 Key Laboratory of Submarine Geosciences,State Oceanic Administrator,Hangzhou 310012,China 5 department of Geology and Geophysics,Woods Hole Oceanographic Institution,Woods Hole,MA 02543,USA Institute of geodesy and Geophysics Chinese Academy of Sciences Wuhan 430077 China

This study investigates the relationship between the hotspot-ridge interaction and the formation of oceanic plateaus and seamounts in the Southwest Indian Ocean.We first calculated the relative distance between the Southwest Indian Ridge (SWIR) and relevant hotspots on the basis of models of plate reconstruction,and then calculated the corresponding excess magmatic anomalies of the hotspots on the basis of residual bathymetry and Airy isostasy.The results reveal that the activities of the Marion hotspot can be divided into three main phases:interaction with the paleo-Rodrigues triple junction (73.6-68.5 Ma),interaction with the SWIR (68.5-42.7 Ma),and intra-plate volcanism (42.7-0 Ma).These three phases correspond to the formation of the eastern,central,and western parts of the Del Cano Rise,respectively.The magnitude and apparent periodicity of the magmatic volume flux of the Marion hotspot appear to be dominated by the hotspot-ridge distance.The periodicity of the Marion hotspot is about 25 Ma,which is much longer than that of the Hawaii and Iceland hotspots (about 15 Ma).

关键词：南印度洋相互作用板内洋脊西南海山高原海洋

ETH-GQS: An estimation of geoid-to-quasigeoid separation over Ethiopia

在线全文

学校读者我要写书评

暂无评论

geodesy and Geodynamics 2022年第1期13卷 31-37页

作者： Ephrem Y.Belay Walyeldeen Godah Malgorzata Szelachowska Robert Tenzer Ethiopian Space Science and Technology Institute Addis Ababa Ethiopia Centre of geodesy and Geodynamics Institute of Geodesy and Cartography(IGiK)WarsawPoland department of Land Surveying and Geo-Informatics Hong Kong Polytechnic UniversityHong KongChina

The determination of accurate orthometric or normal heights remains one of the main challenges for the geodetic community in Ethiopia.These heights are required for geodetic and geodynamic scientific research as well as for extensive engineering applications.The main objective of this study is to estimate the geoid-to-quasi geoid separation(GQS)in Ethiopia(ETH-GQS).Such separation would be required for the conversion between geoid and quasigeoid models,which is mandatory for the determination of accurate geodetic heights in mountain regions.The airborne free-air gravity anomalies and the topo-graphic information retrieved from the SRTM3(Shuttle Radar Topography Mission of a spatial resolution 3 arc-second)digital elevation model were used to compute the ETH-GQS model according to the Sjoberg's strict formula for the geoid-to-quasigeoid separation.The ETH-GQS was then validated using GNSS-levelling data as well as geoid heights determined from different Global Geopotential Models(GGMs),namely the EGM2008,EIGEN-6C4 and GECO.The results reveal that the standard deviation of differences between the geoid heights obtained from the EIGEN-6C4 model and the geometric geoid heights obtained from GNSS-levelling data were improved by~75%(i.***.from~24 to~6 cm)when considering GQS values obtained from the ETH-GQS.

关键词： Geoid-to-quasigeoid separation GNSS-Levelling Ethiopian vertical control network Orthometric and normal heights Airborne gravity data