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1
Dobelis, Didzis, and Jānis Zvirgzds. "NETWORK RTK PERFORMANCE ANALYSIS: A CASE STUDY IN LATVIA." Geodesy and cartography 42, no. 3 (September 22, 2016): 69–74. http://dx.doi.org/10.3846/20296991.2016.1226383.
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Nowadays the RTK (Real Time Kinematic) method for positioning is used in daily life by different consumers for many purposes. Several different RTK correction techniques are used, starting from single site to network approaches. The GNSS market is filled with receivers from different manufacturers and different capabilities. In this paper we assess the stability of the reference station network transmitted RTK correction. Two different surveying class GNSS receivers in combination with four varied RTK correction techniques under diverse observation conditions are analyzed. This study has been conducted in Latvia, where state wide permanent GNSS reference station network has been maintained since year 2005.
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Bisnath, S., A. Saeidi, J. G. Wang, and G. Seepersad. "Evaluation of Network RTK Performance and Elements of Certification—A Southern Ontario Case Study." GEOMATICA 67, no. 4 (December 2013): 243–51. http://dx.doi.org/10.5623/cig2013-050.
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Over the past decade, network RTK technology has become popular as an efficient method of precise, real-time positioning. Its relatively low-cost and single receiver ease-of-use has allowed it to mostly replace static relative GPS and single baseline RTK in urban areas where such networks are economically viable (e.g., cadastral and construction survey). The Ministry of Transportation of Ontario (MTO) and York University have investigated the performance of commercial network RTK services in Southern Ontario, where performance is defined by a set of developed metrics. It was found that the user horizontal solution had an overall precision of ∼2.5 cm (95%), though there were cases of solution biases, drifts and gaps. A follow-up study is developing criteria and pathways for the certification of such commercial network RTK services, focusing on: reference station integration, reference station maintenance, and user solution monitoring. A set of recommendations for network certification is in preparation.
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Aykut, Nedim Onur, Engin Gülal, and Burak Akpinar. "Performance of Single Base RTK GNSS Method versus Network RTK." Earth Sciences Research Journal 19, no. 2 (December 17, 2015): 135–39. http://dx.doi.org/10.15446/esrj.v19n2.51218.
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<p>After the late 1990s, GNSS/GPS network RTK technology has become the preferred technique in the world, today widely used in various applications such as monitoring, early warning systems, and mapping and engineering applications. By the end of 2008, the CORS-TR network was being used for engineering applications to determine 3D positions across the whole of Turkey. On the other hand, single base RTK stations are being operated in Turkey. The YLDZ is one of these types of stations. It was established at the Yıldız Technical University by the Department of Geomatic Engineering in 2012. In this paper, the performance of the YLDZ station is examined by use of measurements in 5 Istanbul GPS Triangulation Network (IGNA) benchmark points, with five repeatability measurements up to 50 km from the station. The CORS-TR network RTK solution is used at the same points, and the results are compared. The measured coordinates produced by the two RTK solutions are compared with the IGNA point coordinates. Satellite geometry, initialisation time and the standard deviation of repeatability are also determined. The differences between measured and known coordinates are calculated as 1-2 cm horizontally and close to 3 cm vertically using the YLDZ single base RTK method.</p><p> </p><p><strong>Desempeño de un Método de Navegación Cinética Satelital en Tiempo Real (RTK) de una Sola Base en Comparación de un Sistema RTK</strong></p><p> </p><p><strong>Resumen</strong></p><p>Después de la década de los 90, el Sistema Global de Navegación por satélite/Sistema de Posicionamiento Global (GNSS/GPS, en inglés), basado en tecnología de Navegación Cinética Satelital en Tiempo Real (RTK, del inglés Real Time Kinematic) se convirtió en la técnica preferida en el mundo y que todavía se utiliza en varias aplicaciones como el monitoreo, sistemas de alerta temprana y mapeo e ingeniería de aplicativos. Para finales de 2008, los aplicativos de ingeniería utilizan la red de Estaciones de Referencia de Funcionamiento Continuo (CORS-TR, un proyecto establecido en Turquía) para determinar posiciones en tres dimensiones a lo largo del territorio turco. Por otro lado, las estaciones RTK de una sola base han funcionado en Turquía. La YLDZ es una estación de este tipo que fue establecida en la Universidad Técnica de Yildiz por el departamento de Ingeniería Geomática en 2012. En este trabajo se examina el desempeño dela estación YLDZ a través de la medición de cinco puntos de referencia del Sistema de Triangulación GPS de Estambul (IGNA, en inglés) con cinco mediciones repetitivas a más de 50 km de la estación. Similares medidas RTK se hicieron con la red CORS-TR y se compararon los resultados. Las dos mediciones producidas por las soluciones RTK se compararon con los puntos de coordenadas IGNA. También se determinó la geometría satelital, el tiempo de inicialización y la desviación estándar de la repetibilidad. Las diferencias entre las coordenadas medidas y las coordenadas conocidas se calcularon en un rango de 1-2 centímetros horizontalmente y cerca de 3 centímetros verticalmente para la estación YLDZ con el método RTK.</p>
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Chiuman, Novie, Dedi Atunggal, and Nurrohmat Widjajanti. "Analisis Tingkat Ketersediaan dan Cakupan dari Continuously Operating Reference Station (CORS) di Pulau Jawa." JGISE: Journal of Geospatial Information Science and Engineering 4, no. 1 (June 30, 2021): 30. http://dx.doi.org/10.22146/jgise.63277.
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Ketersediaan layanan dan cakupan Continuously Operating Reference Station (CORS) sangat penting untuk kegiatan yang membutuhkan ketelitian level sentimeter atau lebih baik. Penelitian ini menganalisis ketersediaan layanan CORS Indonesia berdasar data web scraping server InaCORS pada Desember 2018. Cakupan CORS diestimasi dengan asumsi performansi Real Time Kinematic (RTK) single base hingga radius 30 kilometer dan untuk RTK network base hingga 50 kilometer dari masing-masing stasiun yang kemudian dipadukan dengan data cakupan jaringan komunikasi selular Telkomsel, Indosat dan 3 dari opensignal.com. Hasil web scraping menunjukkan terdapat 51 stasiun CORS dengan ketersediaan layanan di atas 80%, empat dengan ketersediaan layanan di bawah 80%, dua dengan ketersediaan layanan di bawah 50%, dan 14 yang tidak memiliki ketersediaan layanan. Cakupan CORS untuk metode RTK single base dan network base masing-masing adalah 72,942% dan 98,299%. Luas cakupan CORS terbesar diperoleh provider Telkomsel baik untuk metode RTK single base maupun network base yaitu masing-masing sebesar 34,622% dan 45,180%. Cakupan riil dari estimasi tersebut mungkin lebih besar karena hasil uji lapangan membuktikan bahwa tingkat ketepatan data dari OpenSignal hanya sebesar 69,444% dan masih banyak area tanpa data sinyal. Hasil analisis tingkat duplikasi cakupan CORS menunjukkan bahwa luas duplikasi cakupan CORS untuk metode RTK single base dan network base masing-masing sebesar 37,076% dan 82,382% dari luas total cakupan CORS. Hasil dari penelitian juga menunjukkan setidaknya ada 20 stasiun CORS yang perlu ditingkatkan ketersediaan datanya.
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Zhao, Ya Hong, and Hai Feng Gao. "Analysis and Research of Single Base Station CORS Precision." Applied Mechanics and Materials 405-408 (September 2013): 3027–31. http://dx.doi.org/10.4028/www.scientific.net/amm.405-408.3027.
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Around the single station CORS system, a series of relevant experiments were conducted, the measurement was analyzed. Through base station as the center, different distances of single base station GPS-RTK measurement were carried on , the radius of actual operation and its changing law with the base station distance were obtained concluded , the measurement precision was Obtained by measuring static GPS control points,; the measurement actual coverage area positioning accuracy was confirmed, Internal, extern al accord accuracy was calculated and analyzed., the system actual service radius and The extent of different range accuracy was obtained . the results show that the single base station system is more suitable for the development of small and medium-sized cities, its actual operating radius is 28km, it can completely satisfy the city one or two traverse survey in 18 km.
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Zhang, Baocheng, Peter J. G. Teunissen, and Dennis Odijk. "A Novel Un-differenced PPP-RTK Concept." Journal of Navigation 64, S1 (October 14, 2011): S180—S191. http://dx.doi.org/10.1017/s0373463311000361.
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In this contribution, a novel un-differenced (UD) (PPP-RTK) concept, i.e. a synthesis of Precise Point Positioning and Network-based Real-Time Kinematic concept, is introduced. In the first step of our PPP-RTK approach, the UD GNSS observations from a regional reference network are processed based upon re-parameterised observation equations, corrections for satellite clocks, phase biases and (interpolated) atmospheric delays are calculated and provided to users. In the second step, these network-based corrections are used at the user site to restore the integer nature of his UD phase ambiguities, which makes rapid and high accuracy user positioning possible. The proposed PPP-RTK approach was tested using two GPS CORS networks with inter-station distances ranging from 60 to 100 km. The first test network is the northern China CORS network and the second is the Australian Perth CORS network. In the test of the first network, a dual-frequency PPP-RTK user receiver was used, while in the test of the second network, a low-cost, single-frequency PPP-RTK user receiver was used. The performance of fast ambiguity resolution and the high accuracy positioning of the PPP-RTK results are demonstrated.
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Guo, Qiu Ying, Hong Xia Guo, Bao Min Han, and Ying Sheng Zhang. "Ambiguity Resolution with Single Epoch for GNSS Reference Network Based on Atmospheric Delay Information." Applied Mechanics and Materials 353-356 (August 2013): 3448–51. http://dx.doi.org/10.4028/www.scientific.net/amm.353-356.3448.
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Correct resolution of ambiguities for GNSS reference network is prerequisite for generation of corrections for network RTK. Due to the presence of atmospheric delay in the double-differenced observations, the convergence time of ambiguity is about a dozen minutes and even dozens of minutes for medium and long baselines. And in the case of loss-of-lock or new rising satellites, the integer ambiguities have to be redetermined over and over again. But for the application of GNSS network RTK, the resolution of ambiguity needs to be determined real time as possible. Atmospheric delays of previous epochs are used to predict atmospheric delays of following epochs, and then wide and narrow lane combination of carrier-phase observations as well as ionosphere-free combination is used to resolve ambiguities with single epoch. Our test results show that the precision of predicted double-differenced tropospheric and ionospheric delays is about 2-3 cm using temporal-and spatial-correlation exponent model, and the success rates of L1 ambiguities resolution with single epoch reach above 90% for medium and long distance GNSS reference station network.
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Yang, Wenhao, Yue Liu, and Fanming Liu. "An Improved Relative GNSS Tracking Method Utilizing Single Frequency Receivers." Sensors 20, no. 15 (July 22, 2020): 4073. http://dx.doi.org/10.3390/s20154073.
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The Global Navigation Satellite Systems (GNSS) becomes the primary choice for device localization in outdoor situations. At the same time, many applications do not require precise absolute Earth coordinates, but instead, inferring the geometric configuration information of the constituent nodes in the system by relative positioning. The Real-Time Kinematic (RTK) technique shows its efficiency and accuracy in calculating the relative position. However, when the cycle slips occur, the RTK method may take a long time to obtain a fixed ambiguity value, and the positioning result will be a “float” solution with a low meter accuracy. The novel method presented in this paper is based on the Relative GNSS Tracking Algorithm (Regtrack). It calculates the changes in the relative baseline between two receivers without an ambiguity estimation. The dead reckoning method is used to give out the relative baseline solution while a parallel running Extended Kalman Filter (EKF) method reinitiates the relative baseline when too many validation failures happen. We conducted both static and kinematic tests to assess the performance of the new methodology. The experimental results show that the proposed strategy can give accurate millimeter-scale solutions of relative motion vectors in adjacent two epochs. The relative baseline solution can be sub-decimeter level with or without the base station is holding static. In the meantime, when the initial tracking point and base station coordinates are precisely obtained, the tracking result error can be only 40 cm away from the ground truth after a 25 min drive test in an urban environment. The efficiency test shows that the proposed method can be a real-time method, the time that calculates one epoch of measurement data is no more than 80 ms and is less than 10 ms for best results. The novel method can be used as a more robust and accurate ambiguity free tracking approach for outdoor applications.
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Dabove, Paolo, and Vincenzo Di Pietra. "Single-Baseline RTK Positioning Using Dual-Frequency GNSS Receivers Inside Smartphones." Sensors 19, no. 19 (October 4, 2019): 4302. http://dx.doi.org/10.3390/s19194302.
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Global Navigation Satellite System (GNSS) positioning is currently a common practice thanks to the development of mobile devices such as smartphones and tablets. The possibility to obtain raw GNSS measurements, such as pseudoranges and carrier-phase, from these instruments has opened new windows towards precise positioning using smart devices. This work aims to demonstrate the positioning performances in the case of a typical single-base Real-Time Kinematic (RTK) positioning while considering two different kinds of multi-frequency and multi-constellation master stations: a typical geodetic receiver and a smartphone device. The results have shown impressive performances in terms of precision in both cases: with a geodetic receiver as the master station, the reachable precisions are several mm for all 3D components while if a smartphone is used as the master station, the best results can be obtained considering the GPS+Galileo constellations, with a precision of about 2 cm both for 2D and Up components in the case of L1+L5 frequencies, or 3 cm for 2D components and 2 cm for the Up, in the case of an L1 frequency. Moreover, it has been demonstrated that it is not feasible to reach the phase ambiguities fixing: despite this, the precisions are still good and also the obtained 3D accuracies of positioning solutions are less than 1 m. So, it is possible to affirm that these results are very promising in the direction of cooperative positioning using smartphone devices.
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Tomaszewski, Dariusz, Paweł Wielgosz, Jacek Rapiński, Anna Krypiak-Gregorczyk, Rafał Kaźmierczak, Manuel Hernández-Pajares, Heng Yang, and Raul OrúsPérez. "Assessment of Centre National d’Études Spatiales Real-Time Ionosphere Maps in Instantaneous Precise Real-Time Kinematic Positioning over Medium and Long Baselines." Sensors 20, no. 8 (April 17, 2020): 2293. http://dx.doi.org/10.3390/s20082293.
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Precise real-time kinematic (RTK) Global Navigation Satellite System (GNSS) positioning requires fixing integer ambiguities after a short initialization time. Originally, it was assumed that it was only possible at a relatively short distance from a reference station (<10 km), because otherwise the atmospheric effects prevent effective ambiguity fixing. Nowadays, through the use of VRS, MAC, or FKP corrections, the distances to the closest reference station have been increased to around 35 km. However, the baselines resolved in real time are not as far as in the case of static positioning. Further extension of the baseline requires the use of an ionosphere-weighted model with ionospheric delay corrections available in real time. This solution is now possible thanks to the Radio Technical Commission for Maritime (RTCM) stream of SSR corrections from, for example, Centre National d’Études Spatiales (CNES), the first analysis center to provide it in the context of the International GNSS Service. Then, ionospheric delays are treated as pseudo-observations that have a priori values from the CLK RTCM stream. Additionally, satellite orbit and clock errors are properly considered using space-state representation (SSR) real-time radial, along-track, and cross-track corrections. The following paper presents the initial results of such RTK positioning. Measurements were performed in various field conditions reflecting realistic scenarios that could have been experienced by actual RTK users. We have shown that the assumed methodology was suitable for single-epoch RTK positioning with up to 82 km baseline in solar minimum (30 March 2019) mid and high latitude (Olsztyn, Poland) conditions. We also confirmed that it is possible to obtain a rover position at the level of a few centimeters of precision. Finally, the possibility of using other newer experimental IGS RT Global Ionospheric Maps (GIMs), from Chinese Academy of Sciences (CAS) and Universitat Politècnica de Catalunya (UPC) among CNES, is discussed in terms of their recent performance in the ionospheric delay domain.
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Wang, Jian, Tianhe Xu, Wenfeng Nie, and Guochang Xu. "GPS/BDS RTK Positioning Based on Equivalence Principle Using Multiple Reference Stations." Remote Sensing 12, no. 19 (September 28, 2020): 3178. http://dx.doi.org/10.3390/rs12193178.
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Reliable real-time kinematic (RTK) is crucially important for emerging global navigation satellite systems (GNSSs) applications, such as drones and unmanned vehicles. The performance of conventional single baseline RTK (SBRTK) with one reference station degrades greatly in dense, urban environments, due to signal blockage and multipath error. The increasing use of multiple reference stations for kinematic positioning can improve RTK positioning accuracy and availability in urban areas. This paper proposes a new algorithm for multi-baseline RTK (MBRTK) positioning based on the equivalence principle. The advantages of the solution are to keep observation independent and increase the redundancy to estimate the unknown parameters. The equivalent double-differenced (DD) observation equations for multiple reference stations are firstly developed through the equivalent transform. A modified Kalman filter with parameter constraints is proposed, as well as a partial ambiguity resolution (PAR) strategy is developed to determine an ambiguity subset. Finally, the static and kinematic experiments are carried out to validate the proposed algorithm. The results demonstrate that, compared with single global positioning system (GPS) and Beidou navigation system (BDS) RTK positioning, the GPS/BDS positioning for MBRTK can enhance the positioning accuracy with improvement by approximately (45%, 35%, and 27%) and (12%, 6%, and 19%) in the North (N), East (E), and Up (U) components, as well as the availability with improvement by about 33% and 10%, respectively. Moreover, the MBRTK model with two and three reference receivers can significantly increase the redundancy and provide smaller ambiguity dilution of precision (ADOP) values. Compared with the scheme-one and scheme-two for SBRTK, the MBRTK with multiple reference receivers have a positioning accuracy improvement by about (9%, 0%, and 6%) and (9%, 16%, and 16%) in N, E, and U components, as well as the availability improvement by approximately 10%. Therefore, compared with the conventional SBRTK, the MBRTK can enhance the strength of the kinematic positioning model as well as improve the positioning accuracy and availability.
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Taddia, Yuri, Laura González-García, Elena Zambello, and Alberto Pellegrinelli. "Quality Assessment of Photogrammetric Models for Façade and Building Reconstruction Using DJI Phantom 4 RTK." Remote Sensing 12, no. 19 (September 24, 2020): 3144. http://dx.doi.org/10.3390/rs12193144.
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Aerial photogrammetry by Unmanned Aerial Vehicles (UAVs) is a widespread method to perform mapping tasks with high-resolution to reconstruct three-dimensional (3D) building and façade models. However, the survey of Ground Control Points (GCPs) represents a time-consuming task, while the use of Real-Time Kinematic (RTK) drones allows for one to collect camera locations with an accuracy of a few centimeters. DJI Phantom 4 RTK (DJI-P4RTK) combines this with the possibility to acquire oblique images in stationary conditions and it currently represents a versatile drone widely used from professional users together with commercial Structure-from-Motion software, such as Agisoft Metashape. In this work, we analyze the architectural application of this drone to the photogrammetric modeling of a building with particular regard to metric survey specifications for cultural heritage for 1:20, 1:50, 1:100, and 1:200 scales. In particular, we designed an accuracy assessment test signalizing 109 points, surveying them with total station and adjusting the measurements through a network approach in order to achieve millimeter-level accuracy. Image datasets with a designed Ground Sample Distance (GSD) of 2 mm were acquired in Network RTK (NRTK) and RTK modes in manual piloting and processed both as single façades (S–F) and as an overall block (4–F). Subsequently, we compared the results of photogrammetric models generated in Agisoft Metashape to the Signalized Point (SP) coordinates. The results highlight the importance of processing an overall photogrammetric block, especially whenever part of camera locations exhibited a poorer accuracy due to multipath effects. No significant differences were found between the results of network real-time kinematic (NRTK) and real-time kinematic (RTK) datasets. Horizontal residuals were generally comparable to GNSS accuracy in NRTK/RTK mode, while vertical residuals were found to be affected by an offset of about 5 cm. We introduced an external GCP or used one SP per façade as GCP, assuming a poorer camera location accuracy at the same time, in order to fix this issue and comply with metric survey specifications for the widest architectural scale range. Finally, both S–F and 4–F projects satisfied the metric survey requirements of a scale of 1:50 in at least one of the approaches tested.
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Lu, Yangwei, Shengyue Ji, Rui Tu, Duojie Weng, Xiaochun Lu, and Wu Chen. "An Improved Long-Period Precise Time-Relative Positioning Method Based on RTS Data." Sensors 21, no. 1 (December 24, 2020): 53. http://dx.doi.org/10.3390/s21010053.
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The high precision positioning can be easily achieved by using real-time kinematic (RTK) and precise point positioning (PPP) or their augmented techniques, such as network RTK (NRTK) and PPP-RTK, even if they also have their own shortfalls. A reference station and datalink are required for RTK or NRTK. Though the PPP technique can provide high accuracy position data, it needs an initialisation time of 10–30 min. The time-relative positioning method estimates the difference between positions at two epochs by means of a single receiver, which can overcome these issues within short period to some degree. The positioning error significantly increases for long-period precise positioning as consequence of the variation of various errors in GNSS (Global Navigation Satellite System) measurements over time. Furthermore, the accuracy of traditional time-relative positioning is very sensitive to the initial positioning error. In order to overcome these issues, an improved time-relative positioning algorithm is proposed in this paper. The improved time-relative positioning method employs PPP model to estimate the parameters of current epoch including position vector, float ionosphere-free (IF) ambiguities, so that these estimated float IF ambiguities are used as a constraint of the base epoch. Thus, the position of the base epoch can be estimated by means of a robust Kalman filter, so that the position of the current epoch with reference to the base epoch can be obtained by differencing the position vectors between the base epoch and the current one. The numerical results obtained during static and dynamic tests show that the proposed positioning algorithm can achieve a positioning accuracy of a few centimetres in one hour. As expected, the positioning accuracy is highly improved by combining GPS, BeiDou and Galileo as a consequence of a higher amount of used satellites and a more uniform geometrical distribution of the satellites themselves. Furthermore, the positioning accuracy achieved by using the positioning algorithm here described is not affected by the initial positioning error, because there is no approximation similar to that of the traditional time-relative positioning. The improved time-relative positioning method can be used to provide long-period high precision positioning by using a single dual-frequency (L1/L2) satellite receiver.
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Yu, Chen, Nigel T. Penna, and Zhenhong Li. "Optimizing Global Navigation Satellite Systems network real-time kinematic infrastructure for homogeneous positioning performance from the perspective of tropospheric effects." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 476, no. 2242 (October 2020): 20200248. http://dx.doi.org/10.1098/rspa.2020.0248.
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Real-time centimetre-level precise positioning from Global Navigation Satellite Systems (GNSS) is critical for activities including landslide, glacier and coastal erosion monitoring, flood modelling, precision agriculture, intelligent transport systems, autonomous vehicles and the Internet of Things. This may be achieved via the real-time kinematic (RTK) GNSS approach, which uses a single receiver and a network of continuously operating GNSS reference stations (CORS). However, existing CORS networks have often been established simply by attempting regular spacing or in clusters around cities, with little consideration of weather, climate and topography effects, which influence the GNSS tropospheric delay, a substantial GNSS positional error and which prevents homogeneous RTK accuracy attainment. Here, we develop a framework towards optimizing the design of CORS ground infrastructure, such that tropospheric delay errors reduce to 1.5 mm worth of precipitable water vapour (PWV) globally. We obtain average optimal station spacings of 52 km in local summer and 70 km in local winter, inversely related to the atmospheric PWV variation, with denser networks typically required in the tropics and in mountainous areas. We also consider local CORS network infrastructure case studies, showing how after network modification interpolated PWV errors can be reduced from around 2.7 to 1.4 mm.
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Psychas, Dimitrios, and Sandra Verhagen. "Real-Time PPP-RTK Performance Analysis Using Ionospheric Corrections from Multi-Scale Network Configurations." Sensors 20, no. 11 (May 26, 2020): 3012. http://dx.doi.org/10.3390/s20113012.
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The long convergence time required to achieve high-precision position solutions with integer ambiguity resolution-enabled precise point positioning (PPP-RTK) is driven by the presence of ionospheric delays. When precise real-time ionospheric information is available and properly applied, it can strengthen the underlying model and substantially reduce the time required to achieve centimeter-level accuracy. In this study, we present and analyze the real-time PPP-RTK user performance using ionospheric corrections from multi-scale regional networks during a day with medium ionospheric disturbance. It is the goal of this contribution to measure the impact the network dimension has on the ambiguity-resolved user position through the predicted ionospheric corrections. The user-specific undifferenced ionospheric corrections are computed at the network side, along with the satellite phase biases needed for single-receiver ambiguity resolution, using the best linear unbiased predictor. Such corrections necessitate the parameterization of an estimable user receiver code bias, on which emphasis is given in this study. To this end, we process GPS dual-frequency data from four four-station evenly distributed CORS networks in the United States with varying station spacings in order to evaluate if and to what extent the ionospheric corrections from multi-scale networks can improve the user convergence times. Based on a large number of samples, our experimental results showed that sub-10 cm horizontal accuracy can be achieved almost instantaneously in the ionosphere-weighted partially-ambiguity-fixed kinematic PPP-RTK solutions based on corrections from a network with 68 km spacing. Most of the solutions (90%) were shown to require less than 6.0 min, compared to the ionosphere-float PPP solutions that needed 68.5 min. In case of sparser networks with 115, 174 and 237 km spacing, 50% of the horizontal positioning errors are shown to become less than one decimeter after 1.5, 4.0 and 7.0 min, respectively, while 90% of them require 10.5, 16.5 and 20.0 min. We also numerically demonstrated that the user’s convergence times bear a linear relationship with the network density and get shorter as the density increases, for both full and partial ambiguity resolution.
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Wielgocka, Natalia, Tomasz Hadas, Adrian Kaczmarek, and Grzegorz Marut. "Feasibility of Using Low-Cost Dual-Frequency GNSS Receivers for Land Surveying." Sensors 21, no. 6 (March 11, 2021): 1956. http://dx.doi.org/10.3390/s21061956.
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Global Navigation Satellite Systems (GNSS) have revolutionized land surveying, by determining position coordinates with centimeter-level accuracy in real-time or up to sub-millimeter accuracy in post-processing solutions. Although low-cost single-frequency receivers do not meet the accuracy requirements of many surveying applications, multi-frequency hardware is expected to overcome the major issues. Therefore, this paper is aimed at investigating the performance of a u-blox ZED-F9P receiver, connected to a u-blox ANN-MB-00-00 antenna, during multiple field experiments. Satisfactory signal acquisition was noticed but it resulted as >7 dB Hz weaker than with a geodetic-grade receiver, especially for low-elevation mask signals. In the static mode, the ambiguity fixing rate reaches 80%, and a horizontal accuracy of few centimeters was achieved during an hour-long session. Similar accuracy was achieved with the Precise Point Positioning (PPP) if a session is extended to at least 2.5 h. Real-Time Kinematic (RTK) and Network RTK measurements achieved a horizontal accuracy better than 5 cm and a sub-decimeter vertical accuracy. If a base station constituted by a low-cost receiver is used, the horizontal accuracy degrades by a factor of two and such a setup may lead to an inaccurate height determination under dynamic surveying conditions, e.g., rotating antenna of the mobile receiver.
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Zhang, Q., M. Chen, J. Wu, C. Xu, and F. Wang. "FEASIBILITY VERIFICATION OF VIRTUAL REFERENCE STATION TECHNOLOGY IN GEOLOGICAL HAZARD MONITORING." International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLIII-B1-2021 (June 28, 2021): 235–40. http://dx.doi.org/10.5194/isprs-archives-xliii-b1-2021-235-2021.
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Abstract. The surveying and mapping administrative competent departments in 31 provinces (autonomous regions and municipalities) have built provincial-level satellite navigation and positioning reference stations and data centers, and provided CORS services. This provides a good condition for exploring the application of geological hazard monitoring and early warning using Virtual Reference Station (VRS) service based on CORS. At present, the layout mode of "one point one reference station" is usually adopted, when GNSS is used for geological disaster monitoring and early warning. However, the high deployment cost of this plan limits its largescale promotion and application. Using the existing CORS service resources of natural resource system, this paper carried out the application experiment of virtual reference station in geological hazard monitoring application at Huanglongya geological hazard monitoring site in Shaanxi Province, and assessed the virtual reference station data quality, comparative analyzed the precision of static baseline processing results and GNSS real-time deformation monitoring results. The experimental results show that the overall quality of virtual reference station data is better than that of the monitoring station, and the accuracy of the static baseline calculation results is better than 1.0cm in the X direction, and better than 2.0cm in the Y direction and Z direction, which is similar to the static baseline calculation results formed by the physical reference station. The accuracy of the baseline results of real-time observation data calculation is better than 5mm in horizontal RMS and 15mm in vertical RMS. Therefore, it can be seen that the virtual reference station is feasible to be used as the reference station for geological disaster monitoring. In addition, the application experiment of network RTK real-time dynamic single epoch positioning mode is also carried out in geological hazard monitoring. The experimental results show that the RMS values of all three directions are ±3.7mm, ±9.2mm and ±5.0mm respectively, which meet the precision requirements of GNSS disaster monitoring. Therefore, it is also a feasible scheme for geological disaster monitoring and early warning.
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Forlani, Gianfranco, Fabrizio Diotri, Umberto Morra di Cella, and Riccardo Roncella. "Indirect UAV Strip Georeferencing by On-Board GNSS Data under Poor Satellite Coverage." Remote Sensing 11, no. 15 (July 26, 2019): 1765. http://dx.doi.org/10.3390/rs11151765.
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The so-called Real Time Kinematic (RTK) option, which allows one to determine with cm-level accuracy the Unmanned Aerial Vehicles (UAV) camera position at shooting time, is also being made available on medium- or low-cost drones. It can be foreseen that a sizeable amount of UAV surveys will be soon performed (almost) without Ground Control Points (GCP). However, obstacles to Global Navigation Satellite Systems (GNSS) signal at the optimal flight altitude might prevent accurate retrieval of camera station positions, e.g., in narrow gorges. In such cases, the master block can be georeferenced by tying it to an (auxiliary) block flown at higher altitude, where the GNSS signal is not impeded. To prove the point in a worst case scenario, but under controlled conditions, an experiment was devised. A single strip about 700 m long, surveyed by a multi-copter at 30 m relative flight height, was referenced with cm-level accuracy by joint adjustment with a block flown at 100 m relative flight height, acquired by a fixed-wing UAV provided with RTK option. The joint block orientation was repeated with or without GCP and with pre-calibrated or self-calibrated camera parameters. Accuracy on ground was assessed on a fair number of Check Points (CP). The results show that, even without GCP, the precision is effectively transferred from the auxiliary block projection centres to the object point horizontal coordinates and, with a pre-calibrated camera, also to the elevations.
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Ławniczak, Radzym, and Jarosław Kubiak. "Geometric accuracy of topographical objects at Polish topographic maps." Geodesy and Cartography 65, no. 1 (June 1, 2016): 55–66. http://dx.doi.org/10.1515/geocart-2016-0003.
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Abstract The objective of research concerned verifying the accuracy of the location and shape of selected lakes presented on topographical maps from various periods, drawn up on different scales. The area of research covered lakes situated in North-Western Poland on the Międzychód-Sieraków Lakeland. An analysis was performed of vector maps available in both analogue and digital format. The scales of these studies range from 1:50 000 to 1:10 000. The source materials were current for the years 1907 through 2013. The shape and location of lakes have been verified directly by means of field measurements performed using the GPS technology with an accuracy class of RTK. An analysis was performed of the location and shape of five lakes. The analysed water regions were vectorised, and their vector images were used to determine quantitative features: the area and length of the shoreline. Information concerning the analysed lakes obtained from the maps was verified on the basis of direct field measurements performed using a GPS RTK receiver. Use was made of georeferential corrections provided by the NAVGEO service or a virtual reference station generated by the ASG EUPOS system. A compilation of cartographic and field data formed the basis for a comparison of the actual area and the length of the shoreline of the studied lakes. Cartographic analyses made it possible to single out the most reliable cartographic sources, which could be used for the purposes of hydrographical analyses. The course of shorelines shows the attached map.
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Malinowski, Marcin, and Janusz Kwiecień. "A Comparative Study of Precise Point Positioning (PPP) Accuracy Using Online Services." Reports on Geodesy and Geoinformatics 102, no. 1 (December 1, 2016): 15–31. http://dx.doi.org/10.1515/rgg-2016-0025.
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Abstract Precise Point Positioning (PPP) is a technique used to determine the position of receiver antenna without communication with the reference station. It may be an alternative solution to differential measurements, where maintaining a connection with a single RTK station or a regional network of reference stations RTN is necessary. This situation is especially common in areas with poorly developed infrastructure of ground stations. A lot of research conducted so far on the use of the PPP technique has been concerned about the development of entire day observation sessions. However, this paper presents the results of a comparative analysis of accuracy of absolute determination of position from observations which last between 1 to 7 hours with the use of four permanent services which execute calculations with PPP technique such as: Automatic Precise Positioning Service (APPS), Canadian Spatial Reference System Precise Point Positioning (CSRS-PPP), GNSS Analysis and Positioning Software (GAPS) and magicPPP - Precise Point Positioning Solution (magicGNSS). On the basis of acquired results of measurements, it can be concluded that at least two-hour long measurements allow acquiring an absolute position with an accuracy of 2-4 cm. An evaluation of the impact on the accuracy of simultaneous positioning of three points test network on the change of the horizontal distance and the relative height difference between measured triangle vertices was also conducted. Distances and relative height differences between points of the triangular test network measured with a laser station Leica TDRA6000 were adopted as references. The analyses of results show that at least two hours long measurement sessions can be used to determine the horizontal distance or the difference in height with an accuracy of 1-2 cm. Rapid products employed in calculations conducted with PPP technique reached the accuracy of determining coordinates on a close level as in elaborations which employ Final products.
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Alkan, R. M., and T. Öcalan. "Usability of the GPS Precise Point Positioning Technique in Marine Applications." Journal of Navigation 66, no. 4 (May 9, 2013): 579–88. http://dx.doi.org/10.1017/s0373463313000210.
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This study investigates the accuracy of an online Precise Point Positioning (PPP) service operated by the Geodetic Survey Division of Natural Resources Canada (NRCan), Canadian Spatial Reference System (CSRS)-PPP, by using single/dual-frequency Global Positioning System (GPS) data collected by dual-frequency geodetic-grade and Original Equipment Manufacturer (OEM) board type single-frequency GPS receivers. In this work, a kinematic test was carried out in Halic Bay (Golden Horn), Istanbul, Turkey, to assess the performance of the PPP method in a dynamic environment. Based on this study, it can be concluded that the coordinates estimated from the online CSRS-PPP service have a potential of about metre-level accuracy by processing single frequency data collected by an OEM receiver and about a decimetre to a few centimetres level accuracy by processing dual frequency data collected by a geodetic-grade receiver. In general, results show that the PPP technique has become a significant alternative to the conventional relative (differential) positioning techniques (i.e., Differential GPS (DGPS), Real-time Kinematic (RTK)). The technique does not suffer from the drawbacks of the DGPS technique and has potential to provide the same position accuracy without the requirement for a reference station. Consequently, it has been concluded that the PPP technique may be effectively used in marine applications due to its ease of use and provision of high accuracy, as well as being able to offer reduced field operational costs.
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Duan, Sun, Ouyang, Chen, and Shi. "Reducing the Effect of Positioning Errors on Kinematic Raw Doppler (RD) Velocity Estimation Using BDS-2 Precise Point Positioning." Sensors 19, no. 13 (July 9, 2019): 3029. http://dx.doi.org/10.3390/s19133029.
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In the traditional raw Doppler (RD) velocity estimation method, the positioning error of the pseudorange-based global navigation satellite system (GNSS) single point positioning (SPP) solution affects the accuracy of the velocity estimation through the station-satellite unit cosine vector. To eliminate the effect of positioning errors, this paper proposes a carrier-phase-based second generation of the BeiDou navigation satellite system (BDS-2) precise point positioning (PPP) RD velocity estimation method. Compared with the SPP positioning accuracy of tens of meters, the BDS-2 kinematic PPP positioning accuracy is significantly improved to the dm level. In order to verify the reliability and applicability of the developed method, three dedicated tests, the vehicle-borne, ship-borne and air-borne platforms, were conducted. In the vehicle-borne experiment, the GNSS and inertial navigation system (INS)-integrated velocity solution was chosen as the reference. The velocity accuracy of the BDS-2 PPP RD method was better than that of SPP RD by 28.4%, 27.1% and 26.1% in the east, north and up directions, respectively. In the ship-borne and air-borne experiments, the BDS-2 PPP RD velocity accuracy was improved by 17.4%, 21.4%, 17.8%, and 38.1%, 17.6%, 17.5% in the same three directions, respectively, compared with the BDS-2 SPP RD solutions. The reference in these two tests is the real-time kinematic (RTK) Position Derivation (PD)-based velocity.
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Liao, Shujian, Chenbo Yang, and Dengao Li. "Improving precise point positioning performance based on Prophet model." PLOS ONE 16, no. 1 (January 19, 2021): e0245561. http://dx.doi.org/10.1371/journal.pone.0245561.
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Precision point positioning (PPP) is widely used in maritime navigation and other scenarios because it does not require a reference station. In PPP, the satellite clock bias (SCB) cannot be eliminated by differential, thus leading to an increase in positioning error. The prediction accuracy of SCB has become one of the key factors restricting positioning accuracy. Although International GNSS Service (IGS) provides the ultra-rapid ephemeris prediction part (IGU-P), its quality and real-time performance can not meet the practical application. In order to improve the accuracy of PPP, this paper proposes to use the Prophet model to predict SCB. Specifically, SCB sequence is read from the observation part in the ultra-rapid ephemeris (IGU-O) released by IGS. Next, the SCB sequence between adjacent epochs are subtracted to obtain the corresponding SCB single difference sequence. Then using the Prophet model to predict SCB single difference sequence. Finally, the prediction result is substituted into the PPP positioning observation equation to obtain the positioning result. This paper uses the final ephemeris (IGF) published by IGS as a benchmark and compares the experimental results with IGU-P. For the selected four satellites, compared with the results of the IGU-P, the accuracy of SCB prediction of the model in this paper is improved by about 50.3%, 61.7%, 60.4%, and 48.8%. In terms of PPP positioning results, we use Real-time kinematic (RTK) measurements as a benchmark in this paper. Positioning accuracy has increased by 26%, 35%, and 19% in the N, E, and U directions, respectively. The results show that the Prophet model can improve the performance of PPP.
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Schrader, Thorsten, Jochen Bredemeyer, Marius Mihalachi, Jan Rohde, and Thomas Kleine-Ostmann. "Concept and design of a UAS-based platform for measurements of RF signal-in-space." Advances in Radio Science 14 (September 28, 2016): 1–9. http://dx.doi.org/10.5194/ars-14-1-2016.
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Abstract. Field strength or signal-in-space (SIS) measurements have been performed by using manned helicopters, aircrafts or from ground level using extendable masts. With the availability of unmanned aerial systems (UAS) such as multicopters a new versatile platform for SIS measurements is deployable. Larger types show up to eight individually driven electric motors and controllers (therefore called octocopter). They provide the ability to fly along predefined traces, to hover at waypoints and to initiate other actions when those have been reached. They provide self-levelling and stabilisation and moreover, they may gear at a point of interest regardless of their actual position, e.g. during their flight around a tower. Their payload mainly depends on the platform size and allows integration of complex measurement equipment. Upgrading their navigation capabilities including state-of-the-art global navigation satellite system (GNSS) and ground station transmitter (real-time kinematic – RTK) enables precise localisation of the UAS. For operation in electromagnetic harsh environments a shielding can be considered and integrated into the concept. This paper describes concept and design of an octocopter and its instrumentation, along with applications in recent projects, in which we measure and validate terrestrial navigation systems applied in air traffic and the weather forecast services. Among those are instrumentation landing systems (ILS), VHF omnidirectional radio ranges (VOR), airport traffic and weather radars as well as military surveillance radars, and UHF wind profilers. Especially to investigate the possible interaction of VORs and radars with single wind turbines (WT) or wind power plants has become a major request of economy, military and politics. Here, UAS can be deployed to deliver measurement data investigating this interaction. Once developed and setup to a certain extent, UAS are easy and cost-efficient to operate. Nonetheless, due to their compact size, UAS will have rather low interaction with the electromagnetic field to be measured compared to the operation of manned helicopters.
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Anai, T., N. Kochi, M. Yamada, T. Sasaki, H. Otani, D. Sasaki, S. Nishimura, K. Kimoto, and N. Yasui. "EXAMINATION ABOUT INFLUENCE FOR PRECISION OF 3D IMAGE MEASUREMENT FROM THE GROUND CONTROL POINT MEASUREMENT AND SURFACE MATCHING." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XL-4/W5 (May 11, 2015): 165–70. http://dx.doi.org/10.5194/isprsarchives-xl-4-w5-165-2015.
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As the 3D image measurement software is now widely used with the recent development of computer-vision technology, the 3D measurement from the image is now has acquired the application field from desktop objects as wide as the topography survey in large geographical areas. Especially, the orientation, which used to be a complicated process in the heretofore image measurement, can be now performed automatically by simply taking many pictures around the object. And in the case of fully textured object, the 3D measurement of surface features is now done all automatically from the orientated images, and greatly facilitated the acquisition of the dense 3D point cloud from images with high precision. With all this development in the background, in the case of small and the middle size objects, we are now furnishing the all-around 3D measurement by a single digital camera sold on the market. And we have also developed the technology of the topographical measurement with the air-borne images taken by a small UAV<sup> [1~5]</sup>. <br><br> In this present study, in the case of the small size objects, we examine the accuracy of surface measurement (Matching) by the data of the experiments. And as to the topographic measurement, we examine the influence of GCP distribution on the accuracy by the data of the experiments. Besides, we examined the difference of the analytical results in each of the 3D image measurement software. <br><br> This document reviews the processing flow of orientation and the 3D measurement of each software and explains the feature of the each software. And as to the verification of the precision of stereo-matching, we measured the test plane and the test sphere of the known form and assessed the result. As to the topography measurement, we used the air-borne image data photographed at the test field in Yadorigi of Matsuda City, Kanagawa Prefecture JAPAN. We have constructed Ground Control Point which measured by RTK-GPS and Total Station. And we show the results of analysis made in each of the 3D image measurement software. Further, we deepen the study on the influence of the distribution of GCP on the precision.
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Tahar, K. N. "HEIGHT ACCURACY BASED ON DIFFERENT RTK GPS METHOD FOR ULTRALIGHT AIRCRAFT IMAGES." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XL-3/W3 (August 19, 2015): 287–92. http://dx.doi.org/10.5194/isprsarchives-xl-3-w3-287-2015.
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Height accuracy is one of the important elements in surveying work especially for control point’s establishment which requires an accurate measurement. There are many methods can be used to acquire height value such as tacheometry, leveling and Global Positioning System (GPS). This study has investigated the effect on height accuracy based on different observations which are single based and network based GPS methods. The GPS network is acquired from the local network namely Iskandar network. This network has been setup to provide real-time correction data to rover GPS station while the single network is based on the known GPS station. Nine ground control points were established evenly at the study area. Each ground control points were observed about two and ten minutes. It was found that, the height accuracy give the different result for each observation.
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Smaczynski, Maciej, Beata Medynska-Gulij, and Łukasz Halik. "The visualization of the use of land on the basis of the dynamics of the pedestrian movement from the interval UAV imaging." Abstracts of the ICA 1 (July 15, 2019): 1. http://dx.doi.org/10.5194/ica-abs-1-343-2019.
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<p><strong>Abstract.</strong> The identification and visualization of the real land use based on the dynamics of pedestrian movement was the issue discussed in the research. The observation of the pedestrian movement was made on the basis of interval imaging from the low flight level of oblique projection obtained from the single observation station. That led to the occurrence of blind spots, i.e. spots covered by trees and other objects, on imaging made from the drone, which made it difficult or impossible to observe the pedestrian movement on the parts of the research area.</p><p>In the research the data on the Land and Building Register were used in order to analyze the cadastral and infrastructural construction of the research area. The photogrammetric record was made during the maximum density of the pedestrian movement on the research area of 7&thinsp;ha, located on the university campus.</p><p>The objective of the research was to create cartographic visualizations depicting the real land use with the employment of different mapping methods, diagrams and other forms of graphic presentation of spatial data. The georeference of the imaging obtained was based on the ground control points and its verification was carried out with the use of independent ground control points. The process allowed one to obtain an orthophotomap of the research area with the precision up to 27&thinsp;cm in relation to the coordinates of the ground control points, specified by means of GNSS RTK technology. On the basis of the orthophotomap worked out the location of specific pedestrians was determined with the employment of coordinates. Considering the large scale of the research and its objective, it was necessary to present particular pedestrians, using area spatial objects. The transformation of point objects into area objects was possible thanks to suitable methodology and geomatic transformation.</p><p>Furthermore, thanks to the imaging of the 10-second interval and the geomatic research method it was possible to aggregate area objects that represented pedestrians into the land use area. Identified areas of ‘wild’ land use, on which the pedestrian movement was observed outside the specified communication infrastructure, are particularly noteworthy. Moreover, the aggregation allowed one to solve the problem of blind spots. As a result of the conducted research, numerical statements concerning the area of land use based on the observation of pedestrian movement were obtained, and the acquired spatial data were presented on cartographic visualizations.</p>
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Pál, Márton, Fanni Vörös, István Elek, and Béla Kovács. "Possibilities of high precision GPS data in autonomous driving." Abstracts of the ICA 1 (July 15, 2019): 1–2. http://dx.doi.org/10.5194/ica-abs-1-286-2019.
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<p><strong>Abstract.</strong> A self-driving car is a vehicle that is able to perceive its surroundings and navigate in it without human action. Radar sensors, lasers, computer vision and GPS technologies help it to drive individually (Figure 1). They interpret the sensed information to calculate routes and navigate between obstacles and traffic elements.</p><p>Sufficiently accurate navigation and information about the current position of the vehicle are indispensable for transport. These expectations are fulfilled in the case of a human driver: the knowledge on traffic rules and signs make possible to navigate through even difficult situations. Self-driving systems substitute humans by monitoring and evaluating the surrounding environment and its objects without the background information of the driver. This analysing process is vulnerable. Sudden or unexpected situations may occur but high precision navigation and background GPS databases can complement sensor-detected data.</p><p>The assistance of global navigation has been used in cars for decades. Drivers can easily plan their routes and reach their destination by using car GPS units. However, these devices do not provide accurate positioning: there may be a difference of several metres from the real location. Self-driving cars also use navigation to complement sensor data. Although there are already autonomous system tests on motorways and countryside roads, in densely built-in areas this technology faces complications due to accuracy problems. The dilution of precision (DOP) values can be extremely high in larger settlements because high buildings may hide southern sky (where satellite signs are sensed from on our latitude).</p><p>We can achieve centimetre-level accuracy (if the conditions are ideal) with geodesic RTK (real-time kinematic) GPS systems. This high-precision position data is derived from satellite-based positioning systems. Measurements of the phase of the signal’s carrier wave are real-time corrected by a single reference or an interpolated virtual station.</p><p>In this research we use RTK GPS technology in order to work out a spatial database. These measurements can also be less precise in dense cities, but there is time during fieldwork to try to eliminate inaccuracy. We have chosen a sample area in the inner city of Budapest, Hungary where we located all traffic signs, pedestrian crossings and other important elements. As self-driving cars need precise position data of these terrain objects, we have tried to work with a maximum error of a few decimetres.</p><p>We have examined online map providers if they have feasible data structure and some base data. The implemented structure is similar to OpenStreetMap DB, in which there are already some traffic lights in important crossings. With this preliminary test database, we would like to filter out dangerous situations. If the camera of the car does not see a traffic sign because of a tree or a truck, information about it will be available from the database. If a pedestrian crossing is hardly visible and the sensor does not recognize it, the background GIS data will warn the car that there may be inattentive people on the road.</p><p>A test application has also been developed (Figure 2.), in which our Postgres/Postgis database records have been inserted. In the next phase of the project we try to test our database in the traffic. We plan to drive through the sample area and observe the GPS accuracy in the recognition of the located signs.</p><p>This research aims to achieve higher safety in the field of autonomous driving. By having a refreshable cartographic GIS database in the memory of a self-driving car, there is a smaller chance of risking human life. However, the maintenance demands a high amount of work. Because of this we should concentrate only on the most important signs. Even the cars can be able to supervise the content of the database if there is a large number of them on the road. The frequent production and analysis of point clouds is also an option to get nearer to safe automatized traffic.</p>
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Bernstein, T., and V. Janssen. "Positional uncertainty of network RTK observations in a modern datum." Journal of Geodetic Science 11, no. 1 (January 1, 2021): 38–47. http://dx.doi.org/10.1515/jogs-2020-0116.
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Abstract The Geocentric Datum of Australia 2020 (GDA2020) is Australia’s new and much improved national datum. It is based on a single, nationwide least squares network adjustment that rigorously propagates uncertainty. This paper explores three options to include Network Real-Time Kinematic (NRTK) observations and their Positional Uncertainty (PU) in the survey control network of New South Wales (NSW) via the GDA2020 state adjustment. In the first option, PU is empirically estimated based on a dataset of more than 1,500 observations to obtain values that can be uniformly applied to all NRTK observations. In the second option, PU is calculated for each NRTK observation, based on the coordinate quality indicators provided by the Global Navigation Satellite System (GNSS) equipment. Both options continue to treat NRTK observations as point-based position solutions, resulting in poor correlation with surrounding survey control marks. The third option overcomes this issue by utilising the automatically computed GNSS baselines between NRTK observations and their Virtual Reference Station (VRS) to create a connected network that can be adjusted like a static GNSS network. Using a typical urban NRTK survey in Sydney as an example, it is shown that this method offers a rigorous computation of PU, while maintaining the quick and easy nature of NRTK positioning.
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Mian, O., J. Lutes, G. Lipa, J. J. Hutton, E. Gavelle, and S. Borghini. "ACCURACY ASSESSMENT OF DIRECT GEOREFERENCING FOR PHOTOGRAMMETRIC APPLICATIONS ON SMALL UNMANNED AERIAL PLATFORMS." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XL-3/W4 (March 17, 2016): 77–83. http://dx.doi.org/10.5194/isprs-archives-xl-3-w4-77-2016.
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Efficient mapping from unmanned aerial platforms cannot rely on aerial triangulation using known ground control points. The cost and time of setting ground control, added to the need for increased overlap between flight lines, severely limits the ability of small VTOL platforms, in particular, to handle mapping-grade missions of all but the very smallest survey areas. Applanix has brought its experience in manned photogrammetry applications to this challenge, setting out the requirements for increasing the efficiency of mapping operations from small UAVs, using survey-grade GNSS-Inertial technology to accomplish direct georeferencing of the platform and/or the imaging payload. The Direct Mapping Solution for Unmanned Aerial Vehicles (DMS-UAV) is a complete and ready-to-integrate OEM solution for Direct Georeferencing (DG) on unmanned aerial platforms. Designed as a solution for systems integrators to create mapping payloads for UAVs of all types and sizes, the DMS produces directly georeferenced products for any imaging payload (visual, LiDAR, infrared, multispectral imaging, even video). Additionally, DMS addresses the airframe’s requirements for high-accuracy position and orientation for such tasks as precision RTK landing and Precision Orientation for Air Data Systems (ADS), Guidance and Control. <br><br> This paper presents results using a DMS comprised of an Applanix APX-15 UAV with a Sony a7R camera to produce highly accurate orthorectified imagery without Ground Control Points on a Microdrones md4-1000 platform conducted by Applanix and Avyon. APX-15 UAV is a single-board, small-form-factor GNSS-Inertial system designed for use on small, lightweight platforms. The Sony a7R is a prosumer digital RGB camera sensor, with a 36MP, 4.9-micron CCD producing images at 7360 columns by 4912 rows. It was configured with a 50mm AF-S Nikkor f/1.8 lens and subsequently with a 35mm Zeiss Sonnar T* FE F2.8 lens. Both the camera/lens combinations and the APX-15 were mounted to a Microdrones md4-1000 quad-rotor VTOL UAV. The Sony A7R and each lens combination were focused and calibrated terrestrially using the Applanix camera calibration facility, and then integrated with the APX-15 GNSS-Inertial system using a custom mount specifically designed for UAV applications. The mount is constructed in such a way as to maintain the stability of both the interior orientation and IMU boresight calibration over shock and vibration, thus turning the Sony A7R into a metric imaging solution. <br><br> In July and August 2015, Applanix and Avyon carried out a series of test flights of this system. The goal of these test flights was to assess the performance of DMS APX-15 direct georeferencing system under various scenarios. Furthermore, an examination of how DMS APX-15 can be used to produce accurate map products without the use of ground control points and with reduced sidelap was also carried out. Reducing the side lap for survey missions performed by small UAVs can significantly increase the mapping productivity of these platforms. <br><br> The area mapped during the first flight campaign was a 250m x 300m block and a 775m long railway corridor in a rural setting in Ontario, Canada. The second area mapped was a 450m long corridor over a dam known as Fryer Dam (over Richelieu River in Quebec, Canada). Several ground control points were distributed within both test areas. <br><br> The flight over the block area included 8 North-South lines and 1 cross strip flown at 80m AGL, resulting in a ~1cm GSD. The flight over the railway corridor included 2 North-South lines also flown at 80m AGL. Similarly, the flight over the dam corridor included 2 North-South lines flown at 50m AGL. The focus of this paper was to analyse the results obtained from the two corridors. <br><br> Test results from both areas were processed using Direct Georeferencing techniques, and then compared for accuracy against the known positions of ground control points in each test area. The GNSS-Inertial data collected by the APX-15 was post-processed in Single Base mode, using a base station located in the project area via POSPac UAV. For the block and railway corridor, the basestation’s position was precisely determined by processing a 12-hour session using the CSRS-PPP Post Processing service. Similarly, for the flight over Fryer Dam, the base-station’s position was also precisely determined by processing a 4-hour session using the CSRS-PPP Post Processing service. POSPac UAV’s camera calibration and quality control (CalQC) module was used to refine the camera interior orientation parameters using an Integrated Sensor Orientation (ISO) approach. POSPac UAV was also used to generate the Exterior Orientation parameters for images collected during the test flight. <br><br> The Inpho photogrammetric software package was used to develop the final map products for both corridors under various scenarios. The imagery was first imported into an Inpho project, with updated focal length, principal point offsets and Exterior Orientation parameters. First, a Digital Terrain/Surface Model (DTM/DSM) was extracted from the stereo imagery, following which the raw images were orthorectified to produce an orthomosaic product.
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Mian, O., J. Lutes, G. Lipa, J. J. Hutton, E. Gavelle, and S. Borghini. "ACCURACY ASSESSMENT OF DIRECT GEOREFERENCING FOR PHOTOGRAMMETRIC APPLICATIONS ON SMALL UNMANNED AERIAL PLATFORMS." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XL-3/W4 (March 17, 2016): 77–83. http://dx.doi.org/10.5194/isprsarchives-xl-3-w4-77-2016.
Full textAbstract:
Efficient mapping from unmanned aerial platforms cannot rely on aerial triangulation using known ground control points. The cost and time of setting ground control, added to the need for increased overlap between flight lines, severely limits the ability of small VTOL platforms, in particular, to handle mapping-grade missions of all but the very smallest survey areas. Applanix has brought its experience in manned photogrammetry applications to this challenge, setting out the requirements for increasing the efficiency of mapping operations from small UAVs, using survey-grade GNSS-Inertial technology to accomplish direct georeferencing of the platform and/or the imaging payload. The Direct Mapping Solution for Unmanned Aerial Vehicles (DMS-UAV) is a complete and ready-to-integrate OEM solution for Direct Georeferencing (DG) on unmanned aerial platforms. Designed as a solution for systems integrators to create mapping payloads for UAVs of all types and sizes, the DMS produces directly georeferenced products for any imaging payload (visual, LiDAR, infrared, multispectral imaging, even video). Additionally, DMS addresses the airframe’s requirements for high-accuracy position and orientation for such tasks as precision RTK landing and Precision Orientation for Air Data Systems (ADS), Guidance and Control. <br><br> This paper presents results using a DMS comprised of an Applanix APX-15 UAV with a Sony a7R camera to produce highly accurate orthorectified imagery without Ground Control Points on a Microdrones md4-1000 platform conducted by Applanix and Avyon. APX-15 UAV is a single-board, small-form-factor GNSS-Inertial system designed for use on small, lightweight platforms. The Sony a7R is a prosumer digital RGB camera sensor, with a 36MP, 4.9-micron CCD producing images at 7360 columns by 4912 rows. It was configured with a 50mm AF-S Nikkor f/1.8 lens and subsequently with a 35mm Zeiss Sonnar T* FE F2.8 lens. Both the camera/lens combinations and the APX-15 were mounted to a Microdrones md4-1000 quad-rotor VTOL UAV. The Sony A7R and each lens combination were focused and calibrated terrestrially using the Applanix camera calibration facility, and then integrated with the APX-15 GNSS-Inertial system using a custom mount specifically designed for UAV applications. The mount is constructed in such a way as to maintain the stability of both the interior orientation and IMU boresight calibration over shock and vibration, thus turning the Sony A7R into a metric imaging solution. <br><br> In July and August 2015, Applanix and Avyon carried out a series of test flights of this system. The goal of these test flights was to assess the performance of DMS APX-15 direct georeferencing system under various scenarios. Furthermore, an examination of how DMS APX-15 can be used to produce accurate map products without the use of ground control points and with reduced sidelap was also carried out. Reducing the side lap for survey missions performed by small UAVs can significantly increase the mapping productivity of these platforms. <br><br> The area mapped during the first flight campaign was a 250m x 300m block and a 775m long railway corridor in a rural setting in Ontario, Canada. The second area mapped was a 450m long corridor over a dam known as Fryer Dam (over Richelieu River in Quebec, Canada). Several ground control points were distributed within both test areas. <br><br> The flight over the block area included 8 North-South lines and 1 cross strip flown at 80m AGL, resulting in a ~1cm GSD. The flight over the railway corridor included 2 North-South lines also flown at 80m AGL. Similarly, the flight over the dam corridor included 2 North-South lines flown at 50m AGL. The focus of this paper was to analyse the results obtained from the two corridors. <br><br> Test results from both areas were processed using Direct Georeferencing techniques, and then compared for accuracy against the known positions of ground control points in each test area. The GNSS-Inertial data collected by the APX-15 was post-processed in Single Base mode, using a base station located in the project area via POSPac UAV. For the block and railway corridor, the basestation’s position was precisely determined by processing a 12-hour session using the CSRS-PPP Post Processing service. Similarly, for the flight over Fryer Dam, the base-station’s position was also precisely determined by processing a 4-hour session using the CSRS-PPP Post Processing service. POSPac UAV’s camera calibration and quality control (CalQC) module was used to refine the camera interior orientation parameters using an Integrated Sensor Orientation (ISO) approach. POSPac UAV was also used to generate the Exterior Orientation parameters for images collected during the test flight. <br><br> The Inpho photogrammetric software package was used to develop the final map products for both corridors under various scenarios. The imagery was first imported into an Inpho project, with updated focal length, principal point offsets and Exterior Orientation parameters. First, a Digital Terrain/Surface Model (DTM/DSM) was extracted from the stereo imagery, following which the raw images were orthorectified to produce an orthomosaic product.
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Vargas Jiménez, Carlos A. "Letter from the editor." Earth Sciences Research Journal 19, no. 2 (December 17, 2015): 95–96. http://dx.doi.org/10.15446/esrj.v19n2.54601.
Full textAbstract:
<p>Earth Sciences Research Journal presents its latest issue, Volume 19, number 2, with a positive balance in the eve of 2016 and with the challenges for the future editions. During the last two decades, we have published more than 200 papers in all the spectrum of Earth Sciences. We expect we will be here for many years more. ESRJ is now part of international databases, and we hope to improve our numbers thanks to the tireless word we do every day for our readers. We have accomplished the principal objectives for an international publication -punctuality in our volumes, respect for the authors and the spotlight on the scientific quality. For a fair editorial process, we are part of the open access and its policies of pair blind-review. The time of the operations has been reduced, and the international participation increased.</p><p class="MsoNormal"> </p><p class="MsoNormal">For the coming years, ESRJ would reach a better visibility thanks to the publication of top-quality scientific articles, which allows us to be part of the central positions in international databases and providing researchers with fundamental elements of their work.</p><p class="MsoNormal"> </p><p class="MsoNormal">To make possible this goal, we want to call authors to put lights on scientific quality and editorial quality. Your help is essential for us. We want to encourage researchers to pick up ESRJ as a platform for their works, but also to check the authors' guidelines as a first step to saving efforts and time during processes. Needles to say the importance of manuscript parts, English level and images readability to the acceptation of submissions.</p><p class="MsoNormal"> </p><p class="MsoNormal">As a complementary strategy, we would like to invite our authors to create profiles in one of the available platforms, not only as an introduction to the ESRJ editorial team but also as a promotion of your work.</p><p class="MsoNormal"> </p><p class="MsoNormal">Several challenges we have gripped during the work of the last years, for that reason we have adopted the principles of ethic and best practices in our procedure protocols. This decision would be a tool giving papers’ authors a warranty of complete respect for their work and to readers a quality signature that our contents have been verified for their use.</p><p class="MsoNormal"> </p><p class="MsoNormal">In this adoption of best-practices procedures, many submitted papers have been rejected for having a not proper citation; this fault needs to be eradicated from all journals promoting scientific contents.</p><p class="MsoNormal"> </p><p class="MsoNormal">A glimpse of the numbers of ESRJ points the international collaboration as one of the biggest challenges for the future issues. International Collaboration accounts for the articles that have been produced by researchers from several countries. It's not a call to improve the rates, but the scientific quality would be feed for the interaction of researchers facing different realities.</p><p class="MsoNormal"> </p><p class="MsoNormal">Early 2016, ESRJ will publish a special issue with the selected papers of the International Conference on Earth and Environmental Sciences by the University Malaya. This special issue on Frontiers in Earth Sciences will publish articles on the most outstanding discoveries across a broad research spectrum in the field. The mission of Frontiers in Earth Sciences is to provide an introduction to some of the current advanced concepts, problems, and controversies that are at the forefront of Earth Sciences and to obtain a view of how the different parts of the Earth behave and interact.</p><p class="MsoNormal"> </p><p class="MsoNormal">As it has been a costume in this letter from the editor, the following paragraphs will introduce the works of the current issue. Our first paper deals with the problem of recovering Moho surface from satellite gradiometry data considering the non-isostatic corrections.</p><p class="MsoNormal"> </p><p class="MsoNormal">The second manuscript presents a case study on the application of electromagnetic and GPR measurements to a suspicious metal-contaminated site. While subsurface pollution is very harmful to nature-beings and finally human, detection of its extent in surface and more in depth is considerably challenging.</p><p class="MsoNormal"> </p><p class="MsoNormal">The following work analyzes the Earthquake light phenomenon based in the Christchurch earthquakes occurred in 2010 and 2011, with testimonies related from people who observed or recorded the lights.</p><p class="MsoNormal"> </p><p class="MsoNormal">In the seismotectonic field is presented a paper showing the Strain rate in the North Anatolian Fault Zone (NAFZ), that is one of the most important fault zones of Turkey. Another Turkish submission tried to determine seismic specifications of the Bitlis province in Lake Van basin and used probabilistic seismic hazard analysis for the determination of local site-specific spectra.</p><p class="MsoNormal"> </p><p class="MsoNormal">Also from Turkey, a paper examines the performance of a single base RTK station compared with similar systems and presenting a complete exposure of values and challenges of the system.</p><p class="MsoNormal"> </p><p class="MsoNormal">A contribution from Iran analyzes the magmatic evolution and compositional characteristics of tertiary volcanic rocks associated with the manganese mineralization in a mine located in Central Iran.</p><p class="MsoNormal"> </p><p class="MsoNormal">Also from in Iran, a paper assesses the stability of the rock slopes with various rock mass qualities. The manuscript discusses the combination of RMR and SMR systems to evaluate rock slope stability.</p><p class="MsoNormal"> </p><p class="MsoNormal">From Latin America, a paper makes a contribution to the knowledge of the Tatui Formation, in Brazil, emphasized in Paleontology and Paleoenvironmental considerations.</p><p class="MsoNormal"> </p><p class="MsoNormal">We hope you find useful these contents.</p><p class="MsoNormal"> </p><p class="MsoNormal">Carlos Vargas</p><p class="MsoNormal">Editor in Chief,</p><p class="MsoNormal">Earth Sciences Research Journal.</p>
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Khodabandeh, A. "Single-station PPP-RTK: correction latency and ambiguity resolution performance." Journal of Geodesy 95, no. 4 (March 25, 2021). http://dx.doi.org/10.1007/s00190-021-01490-z.
Full textAbstract:
AbstractSingle-station PPP-RTK is a special case of PPP-RTK in that corrections are computed, instead of a network, by only one single GNSS receiver. The present contribution aims to develop a framework to generate multi-epoch, single-station corrections, thereby providing PPP-RTK users the capability to time-predict corrections that are subject to time delay or latency. By presenting analytical expressions of the user ambiguity variance matrix, we address how the ambiguity resolution performance is driven by the correction latency and therefore by the uncertainty involved in the time-prediction of single-station PPP-RTK corrections. Supported by numerical results, our analytical study shows that the number of satellites and number of frequencies work in tandem to enable one to increase the correction latency, yet ensuring successful single-receiver ambiguity resolution.
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Šugar, Danijel. "ANALYSIS OF POSITIONING RESULTS OBTAINED BY A SINGLE BASE RTK WITH AUTONOMOUS BASE START AND TILT OPTION." САВРЕМЕНА ТЕОРИЈА И ПРАКСА У ГРАДИТЕЉСТВУ 13, no. 1 (June 7, 2018). http://dx.doi.org/10.7251/stp1813231z.
Full textAbstract:
HPPS service of the CROPOS system is today a fast, reliable, precise and commonly used tool for coordinates determination in Croatia. The advantages of a networked RTK method are well known, but in some situations, a single-base RTK method could be a reliable method for coordinates determination, even without a base station having known coordinates. Single-base RTK method with Autonomous base start can be set up on any (unknown) station with a clear sky and GNSS satellites visibility enabled. Differential corrections are usually broadcast to the rover GNSS receiver via a communication link, enabling the coordinates determination with cm-level precision in real time. Simultaneously, the base GNSS receiver collects static observations for base station determination in post-processing and subsequent rover coordinates shift. In this paper, the above mentioned method was tested on the ground, together with TILT option integrated into newest Topcon GNSS receiver.
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Zha, Jiuping, Baocheng Zhang, Teng Liu, and Pengyu Hou. "Ionosphere-weighted undifferenced and uncombined PPP-RTK: theoretical models and experimental results." GPS Solutions 25, no. 4 (August 16, 2021). http://dx.doi.org/10.1007/s10291-021-01169-0.
Full textAbstract:
AbstractPrecise ionospheric information, as like precise satellite orbits, clocks, and code/phase biases, is a critical factor for achieving fast integer ambiguity resolution in precise point positioning (PPP-AR). This study develops an ionosphere-weighted (IW) undifferenced and uncombined PPP real-time kinematic (PPP-RTK) network model using code and phase observations. We introduce between-station single-differenced ionospheric delay pseudo-observations to take advantage of the similar characteristics of ionospheric delays between two receivers tracking the same satellite. The estimable ionospheric parameters are commonly affected by the differential code bias referring to a particular receiver assigned as pivot, which facilitates the ionospheric interpolation at the user side. Then, the kinematic positioning performance of the IW PPP-RTK user model is analyzed and compared with those of PPP-AR without ionospheric corrections, RTK, and IW-RTK models during low and high solar activity days. The results show that for the PPP-RTK model, the positioning errors converge to thresholds of 2 cm for the horizontal components and 5 cm for the vertical component within 20 epochs, and the positioning errors become stable after an initialization of 20 epochs with root-mean-squared (RMS) values of approximately 0.47, 0.58 and 1.66 cm for the east, north and up components, respectively, which are superior to those of the other three models. Owing to the high ionospheric disturbance influence, the RMS values of the east and up components increase by approximately double and the mean time-to-first-fix increases by 61.5% for the PPP-RTK case.
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Botsyo, Sebastian, Bernard Borketey Bortei, and John Ayer. "CORS Usage for GPS Survey in the Greater Accra Region: Advantages, Limitation, and Suggested Remedies." Journal of Geovisualization and Spatial Analysis 4, no. 2 (September 11, 2020). http://dx.doi.org/10.1007/s41651-020-00061-8.
Full textAbstract:
AbstractThe use of Continuously Operating Reference Stations (CORS) enables surveyors to differentially correct static Global Positioning System (GPS) measurements. CORS are designed to support the broad spectrum of post-processed, relative GPS techniques, and applications. Enhancing geospatial positioning applications of CORS data involves the critical role in defining the nation’s geodetic reference system. With the establishment of a coordinated system of CORS, an Online Positioning User Service can become available for processing in single positioning mode to provide corresponding accurate and homogeneous positional coordinates. The Survey and Mapping Division (SMD), Lands Commission of Ghana, has established four CORS in the Greater Accra, and Ashanti, Western and Brong-Ahafo Regions, respectively, to provide a basic CORS network in accordance with the International Terrestrial Reference Frame (ITRF). However, most surveyors continue to reference their works in these regions to ground survey beacons that have been coordinated and adjusted by variable survey methods. This obviously makes homogeneity of data unpredictable. This study explored the extent of usage of existing CORS network established by SMD with particular focus on the CORS in the Greater Accra Region for GPS surveys and to determine its usefulness in ensuring homogeneity in GPS data collection. The professional participatory (interviews) technique was coupled with differential GPS field observations with the CORS as reference in one case and ground control stations as reference in the other in making relatively conclusive analysis. Test results showed that GPS field survey of an approximate range of 23 km away from the Accra CORS yielded an average positional change in Northings and Eastings of − 0.790 m, − 0.176 m and − 0.681 m, − 0.098 m for single and dual frequency, respectively, in different localities within the study area. Beyond a range of 25 km from the Accra CORS, the average positional change in Northings and Eastings are − 0.536 m, − 0.007 m and − 1.370 m, 0.334 m for single and dual frequency respectively. Of 128 geomatic professionals interviewed, 39% are aware of the availability of COR stations in Greater Accra, 61% are unaware, and 28% are aware and users of the Accra CORS whereas 11% are aware but non-users of the Accra COR station. Of all users sampled, 17.5% are regular and frequent users of the Accra COR station and 10.5% are occasional or seldom users. The results show that the Accra CORS is vital to ensuring a uniform homogenous GPS data. However, very few people are using it due to low public awareness of the usefulness of the CORS among professional surveyors and other users and a cumbersome, bureaucratic nature in CORS data acquisition for post-processing and RTK GPS surveys.