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Analysis of the effect of the 2021 Semeru eruption on water vapor content and atmospheric particles using GNSS and remote sensing
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作者 Mokhamad Nur Cahyadi Arizal Bawasir +7 位作者 Syachrul Arief Amien Widodo Meifal Rusli Deni Kusumawardani Yessi Rahmawati Ana Martina Putra Maulida Hilda Lestiana 《Geodesy and Geodynamics》 EI CSCD 2024年第1期33-41,共9页
Mount Semeru,an active volcano in East Java,Indonesia,erupted on December 4,2021,following extreme rainfall that caused an avalanche of hot pyroclastic flows and lava.The tropospheric conditions and dominant particle ... Mount Semeru,an active volcano in East Java,Indonesia,erupted on December 4,2021,following extreme rainfall that caused an avalanche of hot pyroclastic flows and lava.The tropospheric conditions and dominant particle components in the atmosphere can be monitored using Global Navigation Satellite System(GNSS)technology and remote sensing satellites.GNSS signal propagation delay in Precise Point Positioning(PPP)processing can be used to determine Zenith Tropospheric Delay(ZTD)and Precipitable Water Vapor(PWV)variables so that atmospheric conditions can be generated.In addition,by using remote sensing satellite data,it is possible to obtain rainfall data with high temporal resolution as well as the dominant particle and gas content values during eruptions.During the eruption period,the high value of PWV was dominated by the high intensity of precipitation during the rainy season.High rainfall before the eruption caused activity inside the mountain to increase,which occurred in avalanche type eruption.Apart from that,the atmosphere around Semeru was also dominated by SO_(2)content,which spreaded for tens of kilometers.SO_(2)content began to be detected significantly by remote sensing sensors on December 7,2021.In this study,deformation and atmospheric monitoring were also carried out using low-cost GNSS at the Semeru Monitoring Station on September 9-15,2022.The results of the ZTD and ZWD values show the dominance of the wet component,which is directly proportional to rainfall activity in this period. 展开更多
关键词 Semeru GNSS Water vapor RAINFALL SO_(2)
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Optimization of the Use of Spherical Targets for Point Cloud Registration Using Monte Carlo Simulation
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作者 CHAN Ting On XIAO Hang +3 位作者 XIA Linyuan LICHTI Derek D LI Ming Ho DU Guoming 《Journal of Geodesy and Geoinformation Science》 CSCD 2024年第2期18-36,共19页
Registrations based on the manual placement of spherical targets are still being employed by many professionals in the industry.However,the placement of those targets usually relies solely on personal experience witho... Registrations based on the manual placement of spherical targets are still being employed by many professionals in the industry.However,the placement of those targets usually relies solely on personal experience without scientific evidence supported by numerical analysis.This paper presents a comprehensive investigation,based on Monte Carlo simulation,into determining the optimal number and positions for efficient target placement in typical scenes consisting of a pair of facades.It demonstrates new check-up statistical rules and geometrical constraints that can effectively extract and analyze massive simulations of unregistered point clouds and their corresponding registrations.More than 6×10^(7) sets of the registrations were simulated,whereas more than IOO registrations with real data were used to verify the results of simulation.The results indicated that using five spherical targets is the best choice for the registration of a large typical registration site consisting of two vertical facades and a ground,when there is only a box set of spherical targets available.As a result,the users can avoid placing extra targets to achieve insignificant improvements in registration accuracy.The results also suggest that the higher registration accuracy can be obtained when the ratio between the facade-to-target distance and target-to-scanner distance is approximately 3:2.Therefore,the targets should be placed closer to the scanner rather than in the middle between the facades and the scanner,contradicting to the traditional thought. Besides,the results reveal that the accuracy can be increased by setting the largest projected triangular area of the targets to be large. 展开更多
关键词 point cloud registration Monte Carlo simulation optimalization spherical target
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Evalution of the Accuracy and Performance of Multi-GNSS(MGEX)Positioning for Long Baselines by Using Different Software
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作者 Atinc Pirti Mehmet Ali Yücel 《Journal of Geodesy and Geoinformation Science》 CSCD 2023年第4期79-92,共14页
The Global Positioning System(GPS)is a GNSS constellation,but GNSS is not always GPS.GPS is one of the GNSS constellations used around the world.The GNSS constellations include GPS(US),QZSS(Japan),Beidou/BDS(China),Ga... The Global Positioning System(GPS)is a GNSS constellation,but GNSS is not always GPS.GPS is one of the GNSS constellations used around the world.The GNSS constellations include GPS(US),QZSS(Japan),Beidou/BDS(China),Galileo(EU),and GLONASS(Russia).In 1999,the European Commission(EC)proposed the European Galileo satellite navigation system for the first time.A four-phase development was proposed,including public and private sector finance.Galileo was intended for both civilian and government use,and is managed and controlled by civil authorities.Galileo is made up of 30 satellites,a number of globally distributed ground stations,and a ground control and monitoring system,all of which are extremely similar to the structure,format,and layout of GPS.In this study,we investigate GPS/GLONASS/Galileo/Beidou/IRNSS/QZSS Navigation Satellite System integration algorithm for long baselines ranging from 1500 km to 3000 km in China,Japan and Mongolia.The positioning performance with GPS/GLONASS/Galileo/BDS/IRNSS/QZSS,GPS-only,Galileo-only,GLONASS-only and BDS-only,etc.is compared in terms of the positioning accuracy.An improvement of positioning accuracy over long baselines can be found with GPS/GLONASS/Galileo/BDS/QZSS/IRNSS compared with that of GPS-only and that of BDS-only.The obtained differences of the two baselines(Topcon Magnet Tools Software(Multi-GNSS)-(CSRS-PPP(GPS/GLONASS),(Trimble-RTX(GPS/GLONASS),(AUSPOS(GPS/GLONASS))Online Processing Software)by using GPS/GLONASS/Galileo/BDS/QZSS/IRNSS signals is between 40 cm and 111.5 cm on three days. 展开更多
关键词 Multi-GNSS(MGEX) ACCURACY analysis improvement QZSS BEIDOU GALILEO IRNSS
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Performance of GPS and IMU sensor fusion using unscented Kalman filter for precise i-Boat navigation in infinite wide waters
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作者 Mokhamad Nur Cahyadi Tahiyatul Asfihani +1 位作者 Ronny Mardiyanto Risa Erfianti 《Geodesy and Geodynamics》 EI CSCD 2023年第3期265-274,共10页
The Unmanned Surface Vehicle(USV)navigation system needs an accurate,firm,and reliable performance to avoid obstacles,as well as carry out automatic movements during missions.The Global Positioning System(GPS)is often... The Unmanned Surface Vehicle(USV)navigation system needs an accurate,firm,and reliable performance to avoid obstacles,as well as carry out automatic movements during missions.The Global Positioning System(GPS)is often used in these systems to provide absolute position information.However,the GPS measurements are affected by external conditions such as atmospheric bias and multipath effects.This leads to the inability of the stand-alone GPS to provide accurate positioning for the USV systems.One of the solutions to correct the errors of this sensor is by conducting GPS and Inertial Measurement Unit(IMU)fusion.The IMU sensor is complementary to the GPS and not affected by external conditions.However,it accumulates noise as time elapses.Therefore,this study aims to determine the fusion of the GPS and IMU sensors for the i-Boat navigation system,which is a USV developed by Institut Teknologi Sepuluh Nopember(ITS)Surabaya.Using the Unscented Kalman filter(UKF),sensor fusion was carried out based on the state equation defined by the dynamic and kinematic mathematical model of ship motion in 6 degrees of freedom.Then the performance of this model was tested through several simulations using different combinations of attitude measurement data.Two scenarios were conducted in the simulations:attitude measurement inclusion and exclusion(Scenarios I and II,respectively).The results showed that the position estimation in Scenario II was better than in Scenario I,with the Root Mean Square Error(RMSE)value of 0.062 m.Further simulations showed that the presence of attitude measurement data caused a decrease in the fusion accuracy.The UKF simulation with eight measurement parameters(Scenarios A,B and C)and seven measurement parameters(Scenarios D,E and F),as well as analytical attitude movement,indicated that yaw data had the largest noise accumulation compared to roll and pitch. 展开更多
关键词 GPS IMU Fusion sensor 6 DOF USV motion Unscented Kalman filte
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Unscented Kalman filter for a low-cost GNSS/IMU-based mobile mapping application under demanding conditions
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作者 Mokhamad Nur Cahyadi Tahiyatul Asfihani +1 位作者 Hendy Fitrian Suhandri Risa Erfianti 《Geodesy and Geodynamics》 EI CSCD 2024年第2期166-176,共11页
For the last two decades,low-cost Global Navigation Satellite System(GNSS)receivers have been used in various applications.These receivers are mini-size,less expensive than geodetic-grade receivers,and in high demand.... For the last two decades,low-cost Global Navigation Satellite System(GNSS)receivers have been used in various applications.These receivers are mini-size,less expensive than geodetic-grade receivers,and in high demand.Irrespective of these outstanding features,low-cost GNSS receivers are potentially poorer hardwares with internal signal processing,resulting in lower quality.They typically come with low-cost GNSS antenna that has lower performance than their counterparts,particularly for multipath mitigation.Therefore,this research evaluated the low-cost GNSS device performance using a high-rate kinematic survey.For this purpose,these receivers were assembled with an Inertial Measurement Unit(IMU)sensor,which actively transmited data on acceleration and orientation rate during the observation.The position and navigation parameter data were obtained from the IMU readings,even without GNSS signals via the U-blox F9R GNSS/IMU device mounted on a vehicle.This research was conducted in an area with demanding conditions,such as an open sky area,an urban environment,and a shopping mall basement,to examine the device’s performance.The data were processed by two approaches:the Single Point Positioning-IMU(SPP/IMU)and the Differential GNSS-IMU(DGNSS/IMU).The Unscented Kalman Filter(UKF)was selected as a filtering algorithm due to its excellent performance in handling nonlinear system models.The result showed that integrating GNSS/IMU in SPP processing mode could increase the accuracy in eastward and northward components up to 68.28%and 66.64%.Integration of DGNSS/IMU increased the accuracy in eastward and northward components to 93.02%and 93.03%compared to the positioning of standalone GNSS.In addition,the positioning accuracy can be improved by reducing the IMU noise using low-pass and high-pass filters.This application could still not gain the expected position accuracy under signal outage conditions. 展开更多
关键词 LoW-cost GNSS GNSS/IMU Single Point Positioning-IMU(SPP/IMU) Differential GNSS-IMU(DGNSS/IMU) Unscented Kalman Filter(UKF) Outageconditions
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Spatial prediction of landslide susceptibility in western Serbia using hybrid support vector regression(SVR)with GWO,BAT and COA algorithms 被引量:9
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作者 Abdul-Lateef Balogun Fatemeh Rezaie +6 位作者 Quoc Bao Pham Ljubomir Gigović Siniša Drobnjak Yusuf AAina Mahdi Panahi Shamsudeen Temitope Yekeen Saro Lee 《Geoscience Frontiers》 SCIE CAS CSCD 2021年第3期384-398,共15页
In this study,we developed multiple hybrid machine-learning models to address parameter optimization limitations and enhance the spatial prediction of landslide susceptibility models.We created a geographic informatio... In this study,we developed multiple hybrid machine-learning models to address parameter optimization limitations and enhance the spatial prediction of landslide susceptibility models.We created a geographic information system database,and our analysis results were used to prepare a landslide inventory map containing 359 landslide events identified from Google Earth,aerial photographs,and other validated sources.A support vector regression(SVR)machine-learning model was used to divide the landslide inventory into training(70%)and testing(30%)datasets.The landslide susceptibility map was produced using 14 causative factors.We applied the established gray wolf optimization(GWO)algorithm,bat algorithm(BA),and cuckoo optimization algorithm(COA)to fine-tune the parameters of the SVR model to improve its predictive accuracy.The resultant hybrid models,SVR-GWO,SVR-BA,and SVR-COA,were validated in terms of the area under curve(AUC)and root mean square error(RMSE).The AUC values for the SVR-GWO(0.733),SVR-BA(0.724),and SVR-COA(0.738)models indicate their good prediction rates for landslide susceptibility modeling.SVR-COA had the greatest accuracy,with an RMSE of 0.21687,and SVR-BA had the least accuracy,with an RMSE of 0.23046.The three optimized hybrid models outperformed the SVR model(AUC=0.704,RMSE=0.26689),confirming the ability of metaheuristic algorithms to improve model performance. 展开更多
关键词 LANDSLIDE Machine learning METAHEURISTIC Spatial modeling Support vector regression
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Reliability of GPS/GNSS-based positioning in a forestry environment 被引量:2
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作者 R.Cuneyt Erenoglu 《Journal of Forestry Research》 SCIE CAS CSCD 2017年第3期605-614,共10页
The critical environment is one of the main insufficient to positioning. Geodetic observing systems such as the global positioning system (GPS) and the global navigation satellite systems (GNSS) are routinely used... The critical environment is one of the main insufficient to positioning. Geodetic observing systems such as the global positioning system (GPS) and the global navigation satellite systems (GNSS) are routinely used to estimate the contaminating effects by critical environment. In an effort to define the accuracy and reliability of GPS/ GNSS positioning, we investigated the data having con- taminating effects due to forestry environment. Some reliability criteria and geometric concepts were defined and then examined by them. Two sets of data were collected in open sky and closed canopy separately. The analysis of the observed data was performed using the reliability criteria and geometric concepts. The accuracy and reliability of positioning strongly depended on the canopy ratio and satellite availability. The minimum detectable error on baseline was estimated about 2.5 mm under closed canopy. The number of observable satellites and minimal detectable errors were computed for each epoch. The minimal biases on estimated baselines, bias-to-noise ratios for estimating baseline components and probability of success of the integer ambiguity solution were defined in case of forest canopy. Finally, geometric quality could be achieved using the factors of dilution of precision. Thus, the presented accuracy and reliability concepts fulfill the requirement proposed by the global geodetic observing system in forest environment. 展开更多
关键词 ACCURACY CANOPY FORESTRY GPS/GNSS RELIABILITY
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Evaluation of regional ionospheric grid model over China from dense GPS observations 被引量:1
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作者 Xin Zhao Shuanggen Jin +1 位作者 Cetin Mekik Jialiang Feng 《Geodesy and Geodynamics》 2016年第5期361-368,共8页
The current global or regional ionospheric models have been established for monitoring the ionospheric variations. However, the spatial and temporal resolutions are not enough to describe total electron content(TEC)... The current global or regional ionospheric models have been established for monitoring the ionospheric variations. However, the spatial and temporal resolutions are not enough to describe total electron content(TEC) variations in small scales for China. In this paper, a regional ionospheric grid model(RIGM) with high spatial-temporal resolution(0.5 0.5 and 10-min interval) in China and surrounding areas is established based on spherical harmonics expansion from dense GPS measurements provided by Crustal Movement Observation Network of China(CMONOC) and the International GNSS Service(IGS). The correlation coefficient between the estimated TEC from GPS and the ionosonde measurements is 0.97, and the root mean square(RMS) with respect to Center for Orbit Determination in Europe(CODE) Global Ionosphere Maps(GIMs) is 4.87 TECU. In addition, the impact of different spherical harmonics orders and degrees on TEC estimations are evaluated and the degree/order 6 is better. Moreover, effective ionospheric shell heights from300 km to 700 km are further assessed and the result indicates that 550 km is the most suitable for regional ionospheric modeling in China at solar maximum. 展开更多
关键词 Total electron content (TEC) Regional ionospheric grid model Spherical harmonics IRI-2012 IONOSONDE
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Spatiotemporal Modeling of Monthly Precipitation in the Upper Shiyang River Watershed in West Central Gansu,Northwest China 被引量:1
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作者 张存杰 C.P.-A.BOURQUE +1 位作者 孙兰东 Q.K.HASSAN 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 2010年第1期185-194,共10页
This paper outlines a methodology to estimate monthly precipitation surfaces at 1-kin resolution for the Upper Shiyang River watershed (USRW) in northwest China. Generation of precipitation maps is based on the appl... This paper outlines a methodology to estimate monthly precipitation surfaces at 1-kin resolution for the Upper Shiyang River watershed (USRW) in northwest China. Generation of precipitation maps is based on the application of a four-variable genetic algorithm (GA) trained on 10 years of weather and ancillary data, i.e., surface air temperature, relative humidity, Digital Elevation Model-derived estimates of elevation, and time of year collected at 29 weather stations in west-central Gansu and northern Qinghai province. An observed-to-GA predicted data comparison of 10 years of precipitation collected at the 29 weather stations showed that about 84% of the variability in observed values could be explained by the trained GA, including variability in two independent datasets. Point-comparisons of observed and modeled precipitation along an elevation-rainfall gradient demonstrated near-similar spatiotemporal patterns. A precipitation surface for USRW for July, 2005, was developed with the trained GA and input surfaces of surface air temperature and relative humidity generated from Moderate Resolution Imaging Spectroradiometer sensor (MODIS) products of land surface temperature. Spatial tendencies in predicted maximum and minimum values of surface air temperature, relative humidity, and precipitation within a 2-kin radius circle around selected weather stations were in close agreement with the values measured at the weather stations. 展开更多
关键词 genetic algorithms model building MODIS products principal component analysis watershed delineation
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Evaluation of ocean tide loading effects on GPS-estimated precipitable water vapour in Turkey 被引量:2
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作者 Ourbuz Gokhan Shuanggen Jin 《Geodesy and Geodynamics》 2016年第1期32-38,共7页
Global Positioning System (GPS) has been widely used to estimate the total zenith tropo- spheric delay (ZTD) and precipitable water vapour (PWV) for weather prediction and at- mospheric research as a continuous ... Global Positioning System (GPS) has been widely used to estimate the total zenith tropo- spheric delay (ZTD) and precipitable water vapour (PWV) for weather prediction and at- mospheric research as a continuous and all-weather technique. However, estimations of ZTD and PWV are subject to effects of geophysical models with large uncertainties, particularly imprecise ocean tide models of inland seas in Turkey. In this paper, GPS data from Jan. 1, 2010 to Dec. 31, 2011 are processed using GAMIT/GLOBK at four co-located GPS stations (ISTN, ERZR, SAMN, and IZMI) with Radiosonde from the Turkish Met-Office together with several nearby IGS stations. Four widely used ocean tide models are adopted to evaluate their effects on GPS-estimated PWV, such as IERS recommended FES2004, NAO99b, CSR4.0 and GOT00. Five different strategies are taken without ocean tide model and with four ocean tide models, respectively, which are used to evaluate ocean tide models effects on GPS-estimated PWV through comparing with co-located Radiosonde. Results showed that ocean tide models have greatly affected the estimation of the pre- cipitable water vapour at stations near coasts. The ocean tide model FES2004 gave the best results when compared to Radiosonde with +2.12 mm in PWV at stations near coastline. While other ocean tides models agree each other at millimeter level in PWV. However, at inland GPS stations, ocean tide models have less effect on GPS-estimated PWV. 展开更多
关键词 Precipitable water vapour (PWV)Ocean tide modelsGPSRadiosonde
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Removal of Copper from Acid Mine Drainage (AMD) or Acid Rock Drainage (ARD) 被引量:1
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作者 Agabu Shane Xinyang Xu +7 位作者 John Siame Alick Nguvulu Tewodros Mitiku Tena Musango Lungu Sydney Chinyanta Jackson Kawala Victor Mwango Bowa Brian Chirambo 《Journal of Water Resource and Protection》 2021年第7期435-454,共20页
Acid mine drainage is wastewater from a mine having a low pH and an elevated level of dissolved heavy metals. These metals are harmful to aquatic, animal and human life. This paper looks at the removal of copper from ... Acid mine drainage is wastewater from a mine having a low pH and an elevated level of dissolved heavy metals. These metals are harmful to aquatic, animal and human life. This paper looks at the removal of copper from acid mine drainage using ion exchange to less than 1 mg/l. A weak acidic cation resin was used. Spectrophotometric determination of copper with sodium diethyldithiocarbamate was used to determine the copper concentrations in the treated water. Using regression analysis, the experimental results gave a correlation coefficient of 0.977 and a coefficient of determination of 99.5%. Results indicated that the higher the flows rate the shorter the period after which the copper concentration in the treated water reaches 1 mg/l. At pH 3.85 and 5.09, the resin performed better and at pH above 6.62 and between pH 3.0 and below the resin’s does not perform well. The higher the resin height the greater is the resin exchange capacity and the longer it takes for the copper concentration to reach 1 mg/l in the treated water. The higher the wastewater copper concentration the shorter the time it takes the resin to reach 1 mg/l. The results for this experiment indicated that acid mine drainage can be treated well by ion exchange resins, but it is also very important to establish suitable operating conditions. 展开更多
关键词 Acid Mine Drainage COPPER Ion Exchange Resin and Spectrophotometry
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Location Based Services Acceptance and Adoption Evaluation: An Investigation on Mobile Phone Users’ Response to Awareness and Utilization of LBS Technology in Nairobi Kenya 被引量:1
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作者 Charles Busera Wasomi Edward Hunja Waithaka +1 位作者 Moses Karoki Gachari David Ndegwa Kuria 《Journal of Computer and Communications》 2021年第10期60-96,共37页
Location Based Navigation System (LBNS) is a specific Location Based Service (LBS) purely for navigational purpose. These systems resolve position of a user by using GNSS/GPS positioning technologies, to which supplem... Location Based Navigation System (LBNS) is a specific Location Based Service (LBS) purely for navigational purpose. These systems resolve position of a user by using GNSS/GPS positioning technologies, to which supplementary information on goods and services are tagged. The navigation services have become popular and can be installed on mobile phones to provide route information, location of points of interest and user’s current location. LBS has continued to face challenges which include “communication” process towards user reference. Location Based Service System conveys suitable information through a mobile device for effective decision making and reaction within a given time span. This research was geared at understanding the state of LBS technology acceptance and adoption by users in Nairobi Kenya. To do this a quantitative study was carried out through a questionnaire, to investigate mobile phone users’ response on awareness and use of LBS technology. Testing the growth of this technology in this region compared to predictions in previous studies using Technology Acceptance Model (TAM), it is evident that many users may be aware of GPS functionality in mobile phones but are certainly yet to fully embrace the technology as they rarely use it. This points to some underlying challenges towards this technology within this part of the World, thereby recommending for deliberate monitoring and evaluation of LBS technology for sustenance growth based on user satisfaction and acceptance for improved usability. 展开更多
关键词 Location Based Services (LBS) SMARTPHONE Mobile Device Mobile Phone Location Based Navigation Service (LBNS) Technology Acceptance Model Quantitative Analysis
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Quantitative Assessment of Remotely Sensed Global Surface Models Using Various Land Classes Produced from Landsat Data in Istanbul
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作者 Naci YASTIKLI Umut G SEFERCIK Fatih ESIRTGEN 《Chinese Geographical Science》 SCIE CSCD 2014年第3期307-316,共10页
Digital elevation model (DEM) is the most popular product for three-dimensional (3D) digital representation of bare Earth surface and can be produced by many techniques with different characteristics and ground sa... Digital elevation model (DEM) is the most popular product for three-dimensional (3D) digital representation of bare Earth surface and can be produced by many techniques with different characteristics and ground sampling distances (GSD). Space-borne opti- cal and synthetic aperture radar (SAR) imaging are two of the most preferred and modern techniques for DEM generation. Using them, global DEMs that cover almost entire Earth are produced with low cost and time saving processing. In this study, we aimed to assess the Satellite pour robservation de la Terre-5 (SPOT-5), High Resolution Stereoscopic (HRS), the Advanced Space-borne Thermal Emission and Reflection Radiometer (ASTER), and the Shuttle Radar Topography Mission (SRTM) C-band global DEMs, produced with space-borne optical and SAR imaging. For the assessment, a reference DEM derived from 1 : 1000 scaled digital photogrammetric maps was used. The study is performed in 100 km2 study area in Istanbul including various land classes such as open land, forest, built-up land, scrub and rough terrain obtained from Landsat data. The analyses were realized considering three vertical accuracy types as fundamental, supplemental, and consolidated, defined by national digital elevation program (NDEP) of USA. The results showed that, vertical accuracy of SRTM C-band DEM is better than optical models in all three accuracy types despite having the largest grid spacing. The result of SPOT-5 HRS DEM is very close by SRTM and superior in comparison with ASTER models. 展开更多
关键词 digital elevation model (DEM) quantitative assessment Satellite pour l'observation de la Terre (SPOT) AdvancedSpace-borne Thermal Emission and Reflection Radiometer (ASTER) Shuttle Radar Topography Mission (SRTM)
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Error analysis and characterization of new MEMS IMU sensors and integration with PPP
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作者 高扬 杜爽 《辽宁工程技术大学学报(自然科学版)》 CAS 北大核心 2013年第4期433-442,共10页
Several new MEMS Inertial Measurement Unit(IMU) sensor products have been released recently with improved performance,which have the potential to support much higher precision applications.New MEMS IMUs include the Na... Several new MEMS Inertial Measurement Unit(IMU) sensor products have been released recently with improved performance,which have the potential to support much higher precision applications.New MEMS IMUs include the NavChip from InterSense,the Nav440 from Crossbow,the Landmark30/40 from GTI,the SDI500 from Systron Donner.Since they are new in the market,currently there is limited information about their error characterization which however is important for the construction of proper error models for their integration with other sensors such as GPS.This paper will investigate the error characterization of two new MEMS IMU sensors,namely the NavChip and Nav440,using Allan variance technique.In addition to identifying different error terms,different stochastic error modeling methods,such as Gauss-Markov(GM) and Autoregressive(AR) processes,will also be investigated to assess the MEMS IMU sensor biases.Investigation to integrate new MEMS IMU sensors with Precise Point Positioning(PPP) will also be conducted to address the re-convergence issues. 展开更多
关键词 MEMS INS IMU PPP GPS integrated navigation analysis CHARACTERIZATION simulation
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Performance analysis of real-time and post-mission kinematic precise point positioning in marine environments
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作者 Serdar Erol Reha Metin Alkan +1 位作者 I.Murat Ozulu Veli Ilçi 《Geodesy and Geodynamics》 2020年第6期401-410,共10页
This article focuses on the performance analysis of both real-time and post-mission kinematic precise point positioning(PPP)in challenging marine environments.For this purpose,a real dynamic experiment lasting 6 h was... This article focuses on the performance analysis of both real-time and post-mission kinematic precise point positioning(PPP)in challenging marine environments.For this purpose,a real dynamic experiment lasting 6 h was carried out on a lake dam in?orum City of Turkey.While the kinematic test was continuing,the real-time PPP coordinates were obtained for each measurement epoch with a commercial real-time PPP(RT-PPP)service,namely the Trimble Center Point RTX.Then the post-mission PPP(PM-PPP)coordinates were calculated by using Multi-GNSS data and the Multi-GNSS Experiment(MGEX)precise products.The kinematic RT-PPP and PM-PPP results showed that the PPP coordinates were consistent with the relative solution at centimetre and decimetre level in horizontal and height components,respectively.This study implies that PPP technique is a powerful tool for highly accurate positioning in both real-time and post-mission modes,even for dynamic applications in harsh environments. 展开更多
关键词 Kinematic survey Precise point positioning Real-time PPP IGS-RTS Global GNSS correction service
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Assessment of Household Access to Groundwater: A Case Study of Gilgil Constituency
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作者 Jenipher Achieng’ Obiero Mercy Mwaniki Benson Kipkemboi Kenduiywo 《Journal of Geographic Information System》 2019年第3期293-308,共16页
In 2000, the United Nations (UN) developed Millennium Development Goals (MDG) with one of its aim being to improve access of potable water supply by 2015 in developing countries. This study thus focused on Kenya’s Gi... In 2000, the United Nations (UN) developed Millennium Development Goals (MDG) with one of its aim being to improve access of potable water supply by 2015 in developing countries. This study thus focused on Kenya’s Gilgil constituency which lies in both arid and semi-arid zones and experiences bimodal rains which are neither heavy nor reliable. With persistent shortages, water management and monitoring became essential and in current times the use of Geographic Information Systems (GIS) is being incorporated due to its capability as an effective tool in water resources management. The study’s aim was to provide knowledge about accessible areas and gaps using cost surface analysis as well as identify other factors that influence settlement. The study utilized walk speeds as an impedance to determine cost surfaces followed by creation of service areas from water facilities using time as a measurement of access. The study established that surface friction may not have major influence on accessibility and service areas while logistic regression established that other factors strongly influence settlement apart from water availability. The study also reveals that 77% of the semi-permanent households in Gilgil have a hard time accessing water as they are outside the 30-minute walk time. 展开更多
关键词 GEOGRAPHY Information Systems WATER ACCESSIBILITY Service Area LOGISTIC Regression Ground WATER
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Clusterization of Surface Water Quality and Its Relation to Climate and Land Use/Cover
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作者 Tahir Ali Akbar Quazi K. Hassan Gopal Achari 《Journal of Environmental Protection》 2013年第4期333-343,共11页
The quality of surface water is rapidly changing due to climatic variations, natural processes, and anthropogenic activities. The objectives of this study were to classify and analyze the surface water quality of 12 m... The quality of surface water is rapidly changing due to climatic variations, natural processes, and anthropogenic activities. The objectives of this study were to classify and analyze the surface water quality of 12 major rivers of Alberta on the basis of 17 parameters during the period of five years (i.e., 2004-2008) using principal component analysis (PCA), total exceedance model and clustering technique. Seven major principal components (PCs) with variability of about 89% were identified. These PCs were the indicators of watershed geology, mineralization and anthropogenic activities related to land use/cover. The seven dominant parameters revealed from the seven PCs were total dissolved solids (TDS), true color (TC), pH, iron (Fe), fecal coliform (FC), dissolved oxygen (DO), and turbidity (TUR). The normalized data of dominant parameters were used to develop a model for obtaining total exceedance. The exceedance values acquired from the total exceedance model were used to determine the patterns for the development of five clusters. The performance of the clusters was compared with the classes obtained in Canadian Water Quality Index (CWQI). Cluster 1, cluster 2, cluster 3, cluster 4 and cluster 5 showed agreements of 85.71%, 83.54%, 90.22%, 80.74%, and 83.40% with their respective CWQI classes on the basis of the data for all rivers during 2004-2008. The water quality was deteriorated in growing season due to snow melting. This methodology could be applied to classify the raw surface water quality, analyze the spatio-temporal trends and study the impacts of the factors affecting the water quality anywhere in the world. 展开更多
关键词 Alberta RIVERS CANADIAN WATER QUALITY Index Clustering GEOGRAPHIC Information System Pattern Recognition Principal Component Analysis River WATER QUALITY
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Use of Rough Sets Theory in Point Cluster and River Network Selection
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作者 Jia Qiu Ruisheng Wang Wenjing Li 《Journal of Geographic Information System》 2014年第3期209-219,共11页
In this paper, we applied the rough sets to the point cluster and river network selection. In order to meet the requirements of rough sets, first, we structuralize and quantify the spatial information of objects by co... In this paper, we applied the rough sets to the point cluster and river network selection. In order to meet the requirements of rough sets, first, we structuralize and quantify the spatial information of objects by convex hull, triangulated irregular network (TIN), Voronoi diagram, etc.;second, we manually assign decisional attributes to the information table according to conditional attributes. In doing so, the spatial information and attribute information are integrated together to evaluate the importance of points and rivers by rough sets theory. Finally, we select the point cluster and the river network in a progressive manner. The experimental results show that our method is valid and effective. In comparison with previous work, our method has the advantage to adaptively consider the spatial and attribute information at the same time without any a priori knowledge. 展开更多
关键词 ROUGH Sets THEORY Map GENERALIZATION POINT CLUSTER River Network Progressive SELECTION
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The Analysis of Scientific and Commercial Softwares Accuracy in GPS Observation Processing
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作者 Morteza Hamidi Peyman Javadi 《Open Journal of Geology》 2017年第3期267-278,共12页
The engineers use various softwares for observation processing and GPS networks, generally everyone who uses a device, he uses softwares with the same brand for the processing of it GPS processing networks by defined ... The engineers use various softwares for observation processing and GPS networks, generally everyone who uses a device, he uses softwares with the same brand for the processing of it GPS processing networks by defined default parameters and models. The most outstanding issue is that, it should be understood, the application of which kinds of softwares will help us to gain the desirable accuracy and whether the accuracy of coordinate estimation is acceptable in all commercial softwares or not. In this article, we compared a series of softwares which engineers use for their data processing with powerful scientific software that meanwhile it is too hard and time consuming to learn it. We have considered accuracy and validity of scientific software, which gives acceptable results, as a baseline to see how much errors and difference is between this software and the commercial softwares, so we selected Bernese as a scientific software and LGO, Ashtech Solutions, CGO softwares as commercial softwares and we analyzed them and compared the applied models of the softwares with each other. To do so, we choose a GPS network from Tehran city and discussed it, in order to evaluate the measured accuracy for baselines and also coordinate system that after data processing, it was understood that if the polygon of a network is small, commercial softwares can be utilized with very high acceptable accuracies and even by Ephemerides Precise data, their accuracy will increase more, but if our network is more extended and bigger, there is no other choice except using scientific softwares to calculate coordinate that performs a processing by many parameters. 展开更多
关键词 Commercial SOFTWARE SCIENTIFIC SOFTWARE GPS BERNESE LGO CGO
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Assessing Water Availability and Unmet Water Demand Using the WEAP Model in the Semi-Arid Bweengwa, Kasaka and Magoye Sub-Catchments of Southern Zambia
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作者 Tewodros M. Tena Alick Nguvulu +1 位作者 Dickson Mwelwa Phenny Mwaanga 《Journal of Environmental Protection》 2021年第4期280-295,共16页
Located in the semi-arid zone of Zambia, the Mutama-Bweengwa, Kasaka and Magoye sub-catchments have witnessed a high demand for water due to increase in population and socio-economic activities putting more pressure o... Located in the semi-arid zone of Zambia, the Mutama-Bweengwa, Kasaka and Magoye sub-catchments have witnessed a high demand for water due to increase in population and socio-economic activities putting more pressure on water resources. This study assesses the hydrological components and ascertains the available water resources and unmet demand in the sub-catchments using the Water Evaluation And Planning (WEAP) Model and hydrometeorological data collected between 1951 and 2018. The model was calibrated and validated on 1971-1981 and 2008-2018 data respectively. The results reveal that the sub-catchments have transitioned from positive to negative water balance with -164.295 Mm<sup>3</sup>/year for Mutama-Bweengwa, -19.021 Mm<sup>3</sup>/year for Kasaka and -86.368 Mm<sup>3</sup>/year for Magoye. Evaporation was 1815.259 Mm<sup>3</sup>/year for Mutama-Bweengwa, 1162.655 Mm<sup>3</sup>/year for Kasaka and 1505.664 Mm<sup>3</sup>/year for Magoye. The demand for water has been increasing over time for various purposes such as irrigation, domestic, urban/rural water supply and livestock. The overall water storage in the sub-catchments showed a negative water balance for the year 2018. The observed and simulated peak streamflow were 8.16 m<sup>3</sup>/s and 7.7 m<sup>3</sup>/s occurring during the month of January and February respectively. The WEAP model performance achieved R<sup>2</sup> of 0.98 during calibration and 0.95 for validation, and an NSE of 0.83 for calibration and 0.85 during validation. The values of objective functions show that the hydrology of the Mutama-Bweengwa, Kasaka and Magoye sub-catchments as predicted by the WEAP model provides satisfactory confidence for prediction of future streamflow and hence projection based on future scenarios. 展开更多
关键词 Water Availability Water Use WEAP Model River Catchment Streamflow Semi-Arid Catchment Hydrology
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