Journal articles on the topic 'GNSS NRTK Quality control'
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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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Famiglietti, Nicola Angelo, Gianpaolo Cecere, Carmine Grasso, Antonino Memmolo, and Annamaria Vicari. "A Test on the Potential of a Low Cost Unmanned Aerial Vehicle RTK/PPK Solution for Precision Positioning." Sensors 21, no. 11 (June 4, 2021): 3882. http://dx.doi.org/10.3390/s21113882.
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This paper investigated the achievable accuracy from a low-cost RTK (Real Time Kinematic)/PPK (Post Processing Kinematic) GNSS (Global Navigation Satellite Systems) system installed on board a UAV (Unmanned Aerial Vehicle), employing three different types of GNSS Bases (Alloy, RS2 and RING) working in PPK mode. To evaluate the quality of the results, a set of seven GCPs (Ground Control Points) measured by means of the NRTK (Network Real Time Kinematic) technique was used. The outcomes show a RMSE (Root Mean Square Error) of 0.0189 m for an ALLOY Base, 0.0194 m for an RS2 Base and 0.0511 m for RING Base, respectively, on the vertical value of DEMs (Digital Elevation Models) obtained by a photogrammetric process. This indicates that, when changing the Base for the PPK, the solutions are different, but they can still be considered adequate for precision positioning with UAVs, especially when GCPs could be used with some difficulty. Therefore, the integration of a RTK/PPK GNSS module on a UAV allows the reconstruction of a highly detailed and precise DEM without using GCPs and provides the possibility to carry out surveys in inaccessible areas.
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Barba, S., M. Barbarella, A. Di Benedetto, M. Fiani, and M. Limongiello. "QUALITY ASSESSMENT OF UAV PHOTOGRAMMETRIC ARCHAEOLOGICAL SURVEY." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-2/W9 (January 31, 2019): 93–100. http://dx.doi.org/10.5194/isprs-archives-xlii-2-w9-93-2019.
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<p><strong>Abstract.</strong> The paper reports the results of a photogrammetric survey made using an Unmanned Aerial Vehicle (UAV) in the archaeological site of the Roman Amphitheatre in Avella (Avellino, Italy). The aim of the study is to verify which modality of image acquisition (if only nadiral images or nadiral plus Oblique images), together with the method of Global Positioning Satellite System (GNSS) survey of the Ground Control Points (GCP) is able to produce the better 3D model, in terms of accuracy, in order to extract traditional graphic drawings (plan, elevation and section), suited to the required representation scales (1<span class="thinspace"></span>:<span class="thinspace"></span>100 and 1<span class="thinspace"></span>:<span class="thinspace"></span>50). The accuracy in georeferencing was evaluated analysing the residues on the GCPs; subsequently, a more detailed analysis of the accuracy of the final 3D model was performed analysing the residuals on the image coordinates, also called re-projection error. The method developed is based on the statistical analysis of the different models, built changing the GCPs survey method and the photogrammetric shots acquired. The results of our analysis show that the photogrammetric survey is more ‘stable’ using only nadiral images and that the nRTK technique allows results comparable to those obtained with static measurements, both in precision and in reliability. Moreover, if the GCPs are measured in nRTK mode, taking into consideration the graphical error, the maximum representation scale is 1<span class="thinspace"></span>:<span class="thinspace"></span>100, whereas the use of static technique makes it possible to describe major details, at a scale of 1<span class="thinspace"></span>:<span class="thinspace"></span>50.</p>
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Amirrudin, Muhammad Afiq, Ami Hassan Md Din, Nur Adilla Zulkifli, Muhammad Asyran Che Amat, and Mohammad Hanif Hamden. "ASSESSMENT OF THE ACCURACY AND PRECISION OF MyRTKnet REAL-TIME SERVICES." Jurnal Teknologi 83, no. 1 (December 7, 2020): 93–103. http://dx.doi.org/10.11113/jurnalteknologi.v83.13892.
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From a network of ninety-six (96) Continuously Operating Reference Stations (CORS), the Department of Survey and Mapping Malaysia (DSMM) has developed a reliable real-time data streaming service known as the Malaysia Real-Time Kinematic GNSS Network (MyRTKnet). MyRTKnet is now operating on Leica SpiderNet system that is configured to provide coordinate to users in Geocentric Datum of Malaysia 2000 (GDM2000). As the name implied, GDM2000 is a geocentric datum for Malaysia, developed based upon the International Terrestrial Reference Frame (ITRF) 2000 or ITRF2000. One could argue that the quality of coordinates provided by MyRTKnet are less optimal as the latest realisation of ITRF at present is ITRF2014. This study aims to investigate the accuracy and precision of the resultant coordinates from MyRTKnet real-time services through a comparison with the control-quality coordinates from a network of post-processed data at some independent points for positioning purpose. Meanwhile for mapping purpose, the coordinates from Network Real-Time Kinematic (NRTK) at selected Cadastral Reference Marks (CRM) points were compared with their known values. The results show that the observed points in ITRF2000 move approximately 37 cm away from the points in ITRF2014 due to the constant movement of Sundaland Block. Meanwhile for the assessment of NRTK technique, there is no significant displacement for coordinates in ITRF2000 but ITRF2014 with the values of 4.4 and 39.8 cm at KDOJ point, respectively. The discrepancy in ITRF2014 could be due to the improper datum transformation procedure.
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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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Tufarolo, E., C. Vanneschi, M. Casella, and R. Salvini. "EVALUATION OF CAMERA POSITIONS AND GROUND POINTS QUALITY IN A GNSS-NRTK BASED UAV SURVEY: PRELIMINARY RESULTS FROM A PRACTICAL TEST IN MORPHOLOGICAL VERY COMPLEX AREAS." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-2/W13 (June 4, 2019): 637–41. http://dx.doi.org/10.5194/isprs-archives-xlii-2-w13-637-2019.
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<p><strong>Abstract.</strong> Open pit mines localized in high mountains are probably one of the most complex environments for Structure-From-Motion (SfM) based photogrammetry. The case study presented in this paper refers to the realization of a detailed topographic mapping in the Torano marble basin (Apuan Alps, Italy) which needed, after decades of excavation activity, a new topographic survey.</p><p>Given the requested very high resolution, the time constraints and safety-related problems, a photogrammetric approach by a fixedwing Unmanned Aerial Vehicle (UAV) was chosen to carry out thesurvey of the basin. In addition, given the morphological complexity of the area, characterized by extreme steep slopes more than hundreds of meters high, and the necessity to minimize the fieldwork without sacrificing the work quality, an UAV equipped with a L1/L2 Network Real Time Kinematic (NRTK) Global Navigation Satellite System (GNSS) was used.</p><p>The scope of this work is to compare the accuracy of UAV derived 3D photogrammetric models realized with different approaches: by using traditional Ground Control Points (GCPs), by using the on-board Network Real Time Kinematic system for camera position detection, and a mix of both. At the end, we tested the quality of the models to verify the reachable levels of accuracy.</p>
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Bae, Tae-Suk, and Minho Kim. "Performance Analysis of Network-RTK Techniques for Drone Navigation considering Ionospheric Conditions." Journal of Sensors 2018 (2018): 1–8. http://dx.doi.org/10.1155/2018/5154697.
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Recently, an accurate positioning has become the kernel of autonomous navigation with the rapid growth of drones including mapping purpose. The Network-based Real-time Kinematic (NRTK) system was predominantly used for precision positioning in many fields such as surveying and agriculture, mostly in static mode or low-speed operation. The NRTK positioning, in general, shows much better performance with the fixed integer ambiguities. However, the success rate of the ambiguity resolution is highly dependent on the ionospheric condition and the surrounding environment of Global Navigation Satellite System (GNSS) positioning, which particularly corresponds to the low-cost GNSS receivers. We analyzed the effects of the ionospheric conditions on the GNSS NRTK, as well as the possibility of applying the mobile NRTK to drone navigation for mapping. Two NRTK systems in operation were analyzed during a period of high ionospheric conditions, and the accuracy and the performance were compared for several operational cases. The test results show that a submeter accuracy is available even with float ambiguity under a favorable condition (i.e., visibility of the satellites as well as stable ionosphere). We still need to consider how to deal with ionospheric disturbances which may prevent NRTK positioning.
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Koivula, Hannu, Jaakko Kuokkanen, Simo Marila, Sonja Lahtinen, and Tuukka Mattila. "Assessment of sparse GNSS network for network RTK." Journal of Geodetic Science 8, no. 1 (December 1, 2018): 136–44. http://dx.doi.org/10.1515/jogs-2018-0014.
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Abstract We tested the accuracy and usability of a sparse GNSS reference station network for network RTK (NRTK) using the Finnish permanent GNSS network FinnRef. We modified the configuration of the FinnRef network stations used in NRTK computation. This allowed us to perform the test both inside and outside of the network area using different NRTK methods and two different RTK receivers. In the test area the average distance between the FinnRef stationswas 160 km. As a comparison,we tested also with the commercial Trimnet and HxGN SmartNet positioning services operated by Geotrim Oy and Leica Geosystems Finland, respectively. Tests showed that the horizontal and vertical rms of Trimnet servicewas 16mmand 40 mm, and of HxGN SmartNet service 23mmand 48 mm. The best rms for the sparse NLS (National Land Survey of Finland) Service was 22 mm and 56 mm. These results indicate that a good NRTK solution can be achieved with a sparser network than typically used. This study also indicates, that the methods for NRTK processing can also affect the quality of the solution.
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Xu, Ying, and Wu Chen. "Performance Analysis of GPS/BDS Dual/Triple-Frequency Network RTK in Urban Areas: A Case Study in Hong Kong." Sensors 18, no. 8 (July 26, 2018): 2437. http://dx.doi.org/10.3390/s18082437.
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Network Real Time Kinematic (NRTK) positioning with instantaneous ambiguity resolution (AR) is currently one of the most popular techniques for real-time precise positioning using Global Navigation Satellite Systems (GNSS) carrier phase observations. Although NRTK has been successfully applied in many fields in surveying and navigation, the initialization speed, accuracy, and ambiguity successfully fixed rate of NRTK in urban areas (Hong Kong, for instance) would be significantly affected by blocked satellite signals. To address these problems and analyze the performance of GPS/BDS dual/triple-frequency NRTK in urban areas, we developed a new Hong Kong GNSS Network RTK Service Platform. Based on this platform, the performance of NRTK in urban areas was examined through a series of experiments. The results showed that: (1) The initialization time of the NRTK varied with the number of the visible satellite and the quality of the observation. (2) Centimeter-level NRTK service could be provided for users over Hong Kong using the Hong Kong GNSS Network RTK Service Platform. (3) In urban areas, GPS/BDS NRTK services for static, walking, and driving users significantly improved the ambiguity successfully fixed rate of the NRTK service when compared with that using the GPS signal alone. The NRTK ambiguity successfully fixed rate in Hong Kong was better than 99% in good environment. In typical urban environment, the RTK ambiguity successfully fixed rate with GPS/BDS was 33.4–72.4%, which was about 12.7–32.4% with GPS only. (4) BDS triple-frequency observation improved the initialization speed and positioning accuracy of RTK in Hong Kong.
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Pepe, Massimiliano. "CORS ARCHITECTURE AND EVALUATION OF POSITIONING BY LOW-COST GNSS RECEIVER." Geodesy and cartography 44, no. 2 (August 8, 2018): 36–44. http://dx.doi.org/10.3846/gac.2018.1255.
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In recent years, the use of low cost GNSS receivers is becoming widespread due to their increasing performance in the spatial positioning, flexibility, ease of use and really interesting price. In addition, a recent technique of Global Navigation Satellite System (GNSS) survey, called Network Real Time Kinematic (NRTK), allows to obtain to rapid and accurate positioning measurements. The main feature of this approach is to use the raw measurements obtained and stored from a network of Continuously Operating Reference Stations (CORS) in order to generate more reliable error models that can mitigate the distance-dependent errors within the area covered by the CORS. Also, considering the huge potential of this GNSS positioning system, the purpose of this paper is to analyze and investigate the performance of the NTRK approach using a low cost GNSS receiver, in stop-and-go kinematic technique. By several case studies it was shown that, using a low cost RTK board for Arduino environment, a smartphone with open source application for Android and the availability of data correction from CORS service, a quick and accurate positioning can be obtained. Because the measures obtained in this way are quite noisy and, more in general, increasing with the baseline, by a simple and suitable statistic treatment, it was possible to increase the quality of the measure. In this way, this low cost architecture could be applied in many geomatics fields. In addition to presenting the main aspects of the NTRK infrastructure and a review of several types of correction, a general workflow in order to obtain quality data in NRTK mode, regardless of the type of GNSS receiver (multi constellations, single or many frequencies, etc.) is discussed.
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McMahon, S., and D. R. Paudyal. "ASSESSING QUALITY OF CORSNET-NSW INFRASTRUCTURE FOR USE IN REGIONAL NEW SOUTH WALES, AUSTRALIA." ISPRS Annals of the Photogrammetry, Remote Sensing and Spatial Information Sciences V-4-2022 (May 18, 2022): 153–61. http://dx.doi.org/10.5194/isprs-annals-v-4-2022-153-2022.
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Abstract. CORSnet-NSW is a network of Global Navigation Satellite System (GNSS) Continuously Operating Reference Stations (CORS) covering the state of NSW and providing centimetre-level real-time positioning. This research paper aims to determine the level of accuracy and precision of CORSnet-NSW in regional parts of the network and compare them to that of traditional RTK under identical conditions. It investigates what effects satellite geometry and proximity to a CORS station have on NRTK measurements. It also verifies the CORSnet-NSW claim of network wide 2cm accuracy. The claim was found to be true at the 68% Confidence Interval. Changes in satellite geometry were not found to affect the results for the most part. It was also found that CORSnet-NSW precision was affected by the proximity of the rover to the base/calibration points more than its proximity to a CORSnet-NSW station. However, even though the CORSnet-NSW results were better than expected, traditional RTK remains the most precise and consistent method. This research paper provides GNSS users in regional NSW with the evidence they need to make informed decisions regarding which type of RTK method is fit for their purposes.
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Akpınar, Burak, and Nedim Onur Aykut. "Determining the Coordinates of Control Points in Hydrographic Surveying by the Precise Point Positioning Method." Journal of Navigation 70, no. 6 (May 24, 2017): 1241–52. http://dx.doi.org/10.1017/s0373463317000236.
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After Global Navigation Satellite Systems (GNSS) were first used in the field of hydrography in 1980, developments in hydrographic surveying accelerated. Survey precision in hydrography has been improved for both horizontal and vertical positioning and seafloor acoustic measurement by means of these new developments. Differential Global Positioning System (DGPS), Real Time Kinematic (RTK) and Network RTK (NRTK) techniques are the satellite-based positioning techniques that are commonly used in shallow water surveys and shoreline measurements. In line with these developments, the newer Precise Point Positioning (PPP) has been introduced. Combining precise satellite positions and clocks with dual-frequency GNSS data, PPP can provide position solutions from the centimetre to decimetre level. In this study, the coordinates of control points were determined by using the Post-Process PPP (PP-PPP) technique. Seven test points, which are the points of the Continuously Operating Reference Station - Turkey (CORS-TR) network, are selected near the shorelines within Turkey. The 24-hour data was split from one to six hours by one hour periods. Automatic Point Positioning Service (APPS) was selected to process the data. The poisoning error of the test points were given and compared with International Hydrographic Organization (IHO) S44 hydrographic survey standards.
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Kim, Hee-Un, and Tae-Suk Bae. "Deep Learning-Based GNSS Network-Based Real-Time Kinematic Improvement for Autonomous Ground Vehicle Navigation." Journal of Sensors 2019 (March 31, 2019): 1–8. http://dx.doi.org/10.1155/2019/3737265.
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Much navigation over the last several decades has been aided by the global navigation satellite system (GNSS). In addition, with the advent of the multi-GNSS era, more and more satellites are available for navigation purposes. However, the navigation is generally carried out by point positioning based on the pseudoranges. The real-time kinematic (RTK) and the advanced technology, namely, the network RTK (NRTK), were introduced for better positioning and navigation. Further improved navigation was also investigated by combining other sensors such as the inertial measurement unit (IMU). On the other hand, a deep learning technique has been recently evolving in many fields, including automatic navigation of the vehicles. This is because deep learning combines various sensors without complicated analytical modeling of each individual sensor. In this study, we structured the multilayer recurrent neural networks (RNN) to improve the accuracy and the stability of the GNSS absolute solutions for the autonomous vehicle navigation. Specifically, the long short-term memory (LSTM) is an especially useful algorithm for time series data such as navigation with moderate speed of platforms. From an experiment conducted in a testing area, the LSTM algorithm developed the positioning accuracy by about 40% compared to GNSS-only navigation without any external bias information. Once the bias is taken care of, the accuracy will significantly be improved up to 8 times better than the GNSS absolute positioning results. The bias terms of the solution need to be estimated within the model by optimizing the layers as well as the nodes each layer, which should be done in further research.
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Syetiawan, Agung, Dudy Darmawan Wijaya, and Irwan Meilano. "Quality control in GNSS reflectometry method for tide observations." TELKOMNIKA (Telecommunication Computing Electronics and Control) 19, no. 6 (December 1, 2021): 1935. http://dx.doi.org/10.12928/telkomnika.v19i6.21670.
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El-Mowafy, Ahmed. "Local Statistical Testing in Quality Control of GNSS Observations." Journal of Global Positioning Systems 9, no. 1 (June 20, 2010): 12–21. http://dx.doi.org/10.5081/jgps.9.1.12.
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Sun, Rui, Ming Qiu, Fei Liu, Zhi Wang, and Washington Yotto Ochieng. "A Dual w-Test Based Quality Control Algorithm for Integrated IMU/GNSS Navigation in Urban Areas." Remote Sensing 14, no. 9 (April 29, 2022): 2132. http://dx.doi.org/10.3390/rs14092132.
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Integration of the Global Navigation Satellite System (GNSS), with Inertial Measurement Unit (IMU) sensors to improve navigation performance, is widely used in many land-based applications. However, further application, especially in urban areas, is limited by the quality (due mainly to multipath effects) and availability of GNSS measurements, with a significant impact on performance, especially from low grade integration. To maximize the potential of GNSS measurements, this paper proposes a dual w-test-based quality control algorithm for integrated IMU/GNSS navigation in urban areas. Quality control is achieved through fault detection and exclusion (FDE) with the capability to detect simultaneous multiple faults in measurements from different satellites. The remaining fault-free GNSS measurements are fused with IMU sensor measurements to obtain the final improved state solution. The effectiveness of the algorithm is validated in a deep urban field test. Compared to the cases without fault exclusion, the results show improvements of about 24% and 30% in horizontal and vertical positioning components, respectively.
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Liu, Haiying, Yang Gao, Yazhou Yue, and Lei Kou. "Carrier-Phase-Based Quality Control for GNSS Dynamic Relative Navigation." Journal of Aerospace Engineering 30, no. 6 (November 2017): 04017067. http://dx.doi.org/10.1061/(asce)as.1943-5525.0000780.
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Taddia, Y., F. Stecchi, and A. Pellegrinelli. "USING DJI PHANTOM 4 RTK DRONE FOR TOPOGRAPHIC MAPPING OF COASTAL AREAS." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-2/W13 (June 4, 2019): 625–30. http://dx.doi.org/10.5194/isprs-archives-xlii-2-w13-625-2019.
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<p><strong>Abstract.</strong> Imagery acquisition systems by Unmanned Aerial Vehicles (UAVs) have been rapidly evolving within the last few years. In mapping applications, it is the introduction of a considerable amount of Ground Control Points (GCPs) that enables the final reconstruction of a real-scale framed model. Since the survey of GCPs generally requires the use of total stations or GNSS receivers in Real Time Kinematic (RTK), either with or without a Network approach (NRTK), this on-site operation is particularly time consuming. In addition, the lack of clearly image-recognizable points may force the use of artificial markers (signalised GCPs) whenever no features are naturally available in the field. This implies a real waste of time for the deployment of the targets, as well as for their recovery. Recently, aircrafts’ manufacturers have integrated the on-board RTK capability on their UAVs. In such a way, the high precision GNSS system allows the 3D position detection of the camera at the time of each capture within few centimetres. In this work, we tested the DJI Phantom 4 RTK for the topographic survey of a coastal section in the Northern Adriatic Sea (Italy). The flights were performed flying at an 80&thinsp;m altitude to ensure a Ground Sample Distance (GSD) of about 2 centimetres. The site extended up to 2 kilometres longitudinally. The results confirm that the on-board RTK approach really speeds up the precise mapping of coastal regions and that a single GCP may be needed to make a reliable estimation of the focal length.</p>
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Hendriatiningsih, Sadikin, Asep Y. Saptari, Sudarman, Ratri Widyastuti, and Putri Rahmadani. "Designing Control Points in UAV-Photogrammetry Mapping Using GNSS Concept to Produce Land Use Map (Case Study: Ciwidey Village, Bandung Regency, Indonesia)." E3S Web of Conferences 94 (2019): 01020. http://dx.doi.org/10.1051/e3sconf/20199401020.
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Production of orhtophoto maps from UAV-photogrammetry method depend on aerial data and control points that are measured by GNSS method. Quality control of orhtophoto maps need comparison coordinate from Check Points and orthophoto maps coordinate to calculate the Root Mean Square Error (RMSE). So that, quality of control points is important in aerial data processing. In this research, baseline length, observation time, measurement method, and area characteristics will be discussed based on the GNSS concept to fulfill the accuracy standard of control points from the American Society of Photogrammetry and Remote Sensing (ASPRS). The shorter baseline length, and the loner observation time, accuracy should be increase significantly, but it depends on the field situation and the accuracy required for the user. After all, the result of this research is to obtain control points design based on GNSS concept in Ciwidey Village, Bandung Regency
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Song, Minfeng, Xiufeng He, Xiaolei Wang, Ye Zhou, and Xueyong Xu. "Study on the Quality Control for Periodogram in the Determination of Water Level Using the GNSS-IR Technique." Sensors 19, no. 20 (October 17, 2019): 4524. http://dx.doi.org/10.3390/s19204524.
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A GNSS station, located on the shore of sea and inland waters, and equipped with standard geodetic receivers and antennas, can be used to measure water levels using a technique called GNSS Interferometric Reflectometry (GNSS-IR). The classical GNSS-IR method is based on SNR data and LSP spectrum analysis method. In order to promote the application of GNSS-IR, the accuracy of the results needs to be further improved, and quality control needs to be achieved better. Classical quality control methods include denoising filtering based on data source SNR; post-processing filtering based on results; morphological analysis based on parameters, such as the ratio of the maximum peak value to the background noise mean, the ratio of the maximum peak to the sub-peak, and the amplitude of the maximum peak. All three methods have the problem of correct frequency extraction under multiple approximate peak conditions. This paper focuses on the performance analysis of three methods of quality control for two situations with real examples, summarizes the advantages and disadvantages of each method, and discusses the measures in applications. Considering the limitations in the threshold setting for the third method, a new quality control method combining multiple parameters and external constraints is proposed. This method is more flexible, especially in dealing with a periodogram with multiple similar peaks, breaking through the premise that the frequency corresponding to the maximum peak is the correct frequency, and validated in two different environments. The experimental results show that the proposed method can improve the accuracy of the measured water level while ensuring the amount of the results. It eliminates the gross errors effectively and uses the data efficiently.
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Balasubramaniam, Rajeswari, and Christopher Ruf. "Neural Network Based Quality Control of CYGNSS Wind Retrieval." Remote Sensing 12, no. 17 (September 3, 2020): 2859. http://dx.doi.org/10.3390/rs12172859.
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Global Navigation Satellite System – Reflectometry (GNSS-R) is a relatively new field in remote sensing that uses reflected GPS signals from the Earth’s surface to study the state of the surface geophysical parameters under observation. The CYGNSS is a first of its kind GNSS-R constellation mission launched in December 2016. It aims at providing high quality global scale GNSS-R measurements that can reliably be used for ocean science applications such as the study of ocean wind speed dynamics, tropical cyclone genesis, coupled ocean wave modelling, and assimilation into Numerical Weather Prediction models. To achieve this goal, strong quality control filters are needed to detect and remove outlier measurements. Currently, quality control of CYGNSS data products are based on fixed thresholds on various engineering, instrument, and measurement conditions. In this work we develop a Neural Network based quality control filter for automated outlier detection of CYGNSS retrieved winds. The primary merit of the proposed ML filter is its ability to better account for interactions between the individual engineering, instrument and measurement conditions than can separate thresholded flags for each one. Use of Machine Learning capabilities to capture inherent patterns in the data can create an efficient and effective mechanism to detect and remove outlier measurements. The resulting filter has a probability of outlier detection (PD) >75% and False Alarm Rate (FAR) < 20% for a wind speed range of 5 to 18 m/s. At least 75% of the outliers with wind speed errors of at least 5 m/s are removed while ~100% of the outliers with wind speed errors of at least 10 m/s are removed. This filter significantly improves data quality. The standard deviation of wind speed retrieval error is reduced from 2.6 m/s without the filter to 1.7 m/s with it over a wind speed range of 0 to 25 m/s. The design space for this filter is also analyzed in this work to characterize trade-offs between PD and FAR. Currently the filter performance is applicable only up to moderate wind speeds, as sufficient data is available only in this range to train the filter, as a way forward, more data over time can help expand the usability of this filter to higher wind speed ranges as well.
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Pourreza, Morteza, Fardin Moradi, Mohammad Khosravi, Azade Deljouei, and Melanie K. Vanderhoof. "GCPs-Free Photogrammetry for Estimating Tree Height and Crown Diameter in Arizona Cypress Plantation Using UAV-Mounted GNSS RTK." Forests 13, no. 11 (November 12, 2022): 1905. http://dx.doi.org/10.3390/f13111905.
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One of the main challenges of using unmanned aerial vehicles (UAVs) in forest data acquisition is the implementation of Ground Control Points (GCPs) as a mandatory step, which is sometimes impossible for inaccessible areas or within canopy closures. This study aimed to test the accuracy of a UAV-mounted GNSS RTK (real-time kinematic) system for calculating tree height and crown height without any GCPs. The study was conducted on a Cupressus arizonica (Greene., Arizona cypress) plantation on the Razi University Campus in Kermanshah, Iran. Arizona cypress is commonly planted as an ornamental tree. As it can tolerate harsh conditions, this species is highly appropriate for afforestation and reforestation projects. A total of 107 trees were subjected to field-measured dendrometric measurements (height and crown diameter). UAV data acquisition was performed at three altitudes of 25, 50, and 100 m using a local network RTK system (NRTK). The crown height model (CHM), derived from a digital surface model (DSM), was used to estimate tree height, and an inverse watershed segmentation (IWS) algorithm was used to estimate crown diameter. The results indicated that the means of tree height obtained from field measurements and UAV estimation were not significantly different, except for the mean values calculated at 100 m flight altitude. Additionally, the means of crown diameter reported from field measurements and UAV estimation at all flight altitudes were not statistically different. Root mean square error (RMSE < 11%) indicated a reliable estimation at all the flight altitudes for trees height and crown diameter. According to the findings of this study, it was concluded that UAV-RTK imagery can be considered a promising solution, but more work is needed before concluding its effectiveness in inaccessible areas.
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Cledat, E., and D. A. Cucci. "MAPPING GNSS RESTRICTED ENVIRONMENTS WITH A DRONE TANDEM AND INDIRECT POSITION CONTROL." ISPRS Annals of Photogrammetry, Remote Sensing and Spatial Information Sciences IV-2/W3 (August 18, 2017): 1–7. http://dx.doi.org/10.5194/isprs-annals-iv-2-w3-1-2017.
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The problem of autonomously mapping highly cluttered environments, such as urban and natural canyons, is intractable with the current UAV technology. The reason lies in the absence or unreliability of GNSS signals due to partial sky occlusion or multi-path effects. High quality carrier-phase observations are also required in efficient mapping paradigms, such as Assisted Aerial Triangulation, to achieve high ground accuracy without the need of dense networks of ground control points. In this work we consider a drone tandem in which the first drone flies outside the canyon, where GNSS constellation is ideal, visually tracks the second drone and provides an indirect position control for it. This enables both autonomous guidance and accurate mapping of GNSS restricted environments without the need of ground control points. We address the technical feasibility of this concept considering preliminary real-world experiments in comparable conditions and we perform a mapping accuracy prediction based on a simulation scenario.
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Mackern, María Virginia, María Laura Mateo, María Fernanda Camisay, and Patricia Alejandra Rosell. "Quality control of SIRGAS ZTD products." Journal of Geodetic Science 12, no. 1 (January 1, 2022): 42–54. http://dx.doi.org/10.1515/jogs-2022-0136.
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Abstract The SIRGAS-CON network currently has more than 450 continuous GNSS stations, and it is used for geodetic purposes. In atmospheric studies, it is used for ionospheric monitoring and for the estimation of zenith tropospheric delays (ZTDs). From the Neutral Atmosphere Analysis Center of SIRGAS, Centro de Ingeniería Mendoza Argentina, the final tropospheric products of this network are generated after several stages of quality controls and filtering, in order to be published on a daily basis in the official website of SIRGAS, since 2014 (https://sirgas.ipgh.org/en/products/tropospheric-delays). These products arise from adjusting the solutions estimated by different SIRGAS analysis centers. Prior to the combination, a quality control of the individual solutions is carried out, based on the precision estimator of each parameter and an internal control of each solution with respect to the combined value. In this work, we show the quality control process of the inputs, the selected tolerance and its justification. The internal consistency analysis of tropospheric parameters for a period of 7 years was carried out. We also exposed the improvements in the estimation of tropospheric parameters implemented during 2021 and its impact in the generation of the final ZTD products (in 99% of the stations the mean standard deviation of ZTD is less than 1 mm).
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Yang, Guanglin, Weihua Bai, Jinsong Wang, Xiuqing Hu, Peng Zhang, Yueqiang Sun, Na Xu, et al. "FY3E GNOS II GNSS Reflectometry: Mission Review and First Results." Remote Sensing 14, no. 4 (February 17, 2022): 988. http://dx.doi.org/10.3390/rs14040988.
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FengYun-3E (FY3E), launched on 5 July 2021, is one of China’s polar-orbiting meteorological satellite series. The GNOS II onboard FY3E is an operational GNSS remote sensor that for the first time combines GNSS radio occultation (GNSS RO) and GNSS reflectometry (GNSS-R). It has eight reflection channels that can track eight specular points at the same time, receiving reflected signals from multiple GNSS systems, including GPS, BeiDou and Galileo. The basic GNSS-R output generated by GNOS II is a 122 × 20 non-uniform delay-Doppler map whose high resolution portion captures more information near the specular point. This paper introduces the GNSS-R aspect of the FengYun-3E GNOS II, including the instrument, power calibration and wind speed retrieval algorithm. Preliminary validation results for its first four months of data are also presented. After preliminary quality control, the overall wind speed error is less than 2 m/s at wind speeds below 20 m/s for data from both GPS satellites and BeiDou satellites when compared to the ECMWF reanalysis winds.
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Sanjaya, Made Ditha Ary, T. Aris Sunantyo, and Nurrohmat Widjajanti. "GEOMETRIC ASPECTS EVALUATION OF GNSS CONTROL NETWORK FOR DEFORMATION MONITORING IN THE JATIGEDE DAM REGION." International Journal of Remote Sensing and Earth Sciences (IJReSES) 15, no. 2 (February 19, 2019): 167. http://dx.doi.org/10.30536/j.ijreses.2018.v15.a2901.
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Many factors led to dam construction failure so that deformation monitoring activities is needed in the area of the dam. Deformation monitoring is performed in order to detect a displacement at the control points of the dam. Jatigede Dam deformation monitoring system has been installed and started to operate, but there has been no evaluation of the geometry quality of control networks treated with IGS points for GNSS networks processing. Therefore, this study aims to evaluate the geometric quality of GNSS control networks on deformation monitoring of Jatigede Dam area. This research data includes the GNSS measurements of five CORS Jatigede Dam stations (R01, GG01, GCP04, GCP06, and GCP08) at doy 233 with network configuration scenarios of 12 IGS points on two quadrants (jat1), three quadrants (jat2), and four quadrants (jat3 and jat4). GNSS networks processing was done by GAMIT to obtain baseline vectors, followed by network processing usingparameter method of least squares adjustment. Networks processing with least squares adjustment aims to determine the most optimal by precision and reliability criterion. Results of this study indicate that network configuration with 12 IGS stations in the two quadrants provides the most accurate coordinates of CORS dam stations. Standard deviations value of CORS station given by jat1 configuration are in the range of 2.7 up to 4.1 cm in X-Z components, whereas standard deviations in the Y component are in the range 5.8 up to 6.9 cm. An optimization assessment based on network strength, precision, and reliability factors shows optimum configuration by jat1.
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Arriola, Jana Sánchez, Magnus Lindskog, Sigurdur Thorsteinsson, and Jelena Bojarova. "Variational Bias Correction of GNSS ZTD in the HARMONIE Modeling System." Journal of Applied Meteorology and Climatology 55, no. 5 (May 2016): 1259–76. http://dx.doi.org/10.1175/jamc-d-15-0137.1.
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AbstractTo fill the gap in the observation system for humidity, the HIRLAM–ALADIN Research on Mesoscale Operational NWP in Euromed (HARMONIE) limited-area high-resolution kilometer-scale model has been prepared for assimilation of Global Navigation Satellite System (GNSS) zenith total delay (ZTD) observations. The observation-processing system includes data selection, bias correction, quality control, and a GNSS observation operator for data assimilation. A large part of the bias between observations and model equivalents comes from the relatively low model top used in the HARMONIE experiments. The functionality of the different observation-processing components was investigated in detail as was the overall performance of the GNSS ZTD data assimilation. This paper contains an extensive description of the GNSS ZTD observation-processing system and a comparison of a newly introduced variational bias correction for GNSS ZTD data with an alternative static bias correction, as well as a detailed analysis of the impact of GNSS ZTD data, both in terms of statistical evaluations over a longer period and in terms of individual case studies. Assimilation of the GNSS ZTD observations with a variational bias correction has improved the quality of short-range weather forecasts for the moisture-related parameters in particular, both in a statistical sense and in individual case studies. The paper also discusses further improvements in the HARMONIE variational data-assimilation system that are needed to fully utilize the potential of high-resolution GNSS ZTD observations.
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Arai, Hironori, Mehrez Zribi, Kei Oyoshi, Karin Dassas, Mireille Huc, Shinichi Sobue, and Thuy Le Toan. "Quality Control of CyGNSS Reflectivity for Robust Spatiotemporal Detection of Tropical Wetlands." Remote Sensing 14, no. 22 (November 21, 2022): 5903. http://dx.doi.org/10.3390/rs14225903.
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The aim of this study was to develop a robust methodology for evaluating the spatiotemporal dynamics of the inundation status in tropical wetlands with the currently available Global Navigation Satellite System-Reflectometry (GNSS-R) data by proposing a new quality control technique called the “precision index”. The methodology was applied over the Mekong Delta, one of the most important rice-production systems comprising aquaculture areas and natural wetlands (e.g., mangrove forests, peatlands). Cyclone Global Navigation Satellite System (CyGNSS) constellation data (August 2018–December 2021) were used to evaluate the spatiotemporal dynamics of the reflectivity Γ over the delta. First, the reflectivity Γ, shape and size of each specular footprint and the precision index were calibrated at each specular point and reprojected to a 0.0045° resolution (approximately equivalent to 500 m) grid at a daily temporal resolution (Lv. 2 product); then, the results were obtained considering bias-causing factors (e.g., the velocity/effective scattering area/incidence angle). The Lv. 2 product was temporally integrated every 15 days with a Kalman smoother (+/− 14 days temporal localization with Gaussian kernel: 1σ = 5 days). By applying the smoother, the regional-annual dynamics over the delta could be clearly visualized. The behaviors of the GNSS-R reflectivity and the Advanced Land Observing Satellite-2 Phased-Array type L-band Synthetic Aperture Radar-2 quadruple polarimetric scatter signals were compared and found to be nonlinearly correlated due to the influence of the incidence angle and the effective scattering area.
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Feng, Xin, Tisheng Zhang, Tao Lin, Hailiang Tang, and Xiaoji Niu. "Implementation and Performance of a Deeply-Coupled GNSS Receiver with Low-Cost MEMS Inertial Sensors for Vehicle Urban Navigation." Sensors 20, no. 12 (June 16, 2020): 3397. http://dx.doi.org/10.3390/s20123397.
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In urban environments, Global Navigation Satellite Systems (GNSS) signals are frequently attenuated, blocked or reflected, which degrades the positioning accuracy of GNSS receivers significantly. To improve the performance of GNSS receiver for vehicle urban navigation, a GNSS/INS deeply-coupled software defined receiver (GIDCSR) with a low cost micro-electro-mechanical system (MEMS) inertial measurement unit (IMU) ICM-20602 is presented, in which both GPS and BDS constellations are supported. Two key technologies, that is, adaptive open-close tracking loops and INS aided pseudo-range weight control algorithm, are applied in the GIDCSR to enhance the signal tracking continuity and positioning accuracy in urban areas. To assess the performance of the proposed deep couple solution, vehicle field tests were carried out in GNSS-challenged urban environments. With the adaptive open-close tracking loops, the deep couple output carrier phase in the open sky, and improved pseudo-range accuracy before and after GNSS signal blocked. Applying the INS aided pseudo-range weight control, the pseudo-range gross errors of the deep couple decreased caused by multipath. A popular GNSS/INS tightly-coupled vehicle navigation kit from u-blox company, M8U, was tested side by side as benchmark. The test results indicate that in the GNSS-challenged urban areas, the pseudo-range quality of GIDCSR is at least 25% better than that of M8U, and GIDCSR’s horizontal positioning results are at least 69% more accurate than M8U’s.
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Bond, Jason, Brian Donahue, Mike Craymer, and Geoff Banham. "NRCan’s Compliance Program for high accuracy, GNSS services: ensuring compatibility with the Canadian Spatial Reference System." Geomatica 72, no. 4 (December 1, 2018): 101–11. http://dx.doi.org/10.1139/geomat-2019-0001.
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There are currently over 700 Global Navigation Satellite System (GNSS) reference stations actively broadcasting corrections (Active Control Stations — ACSs) in Canada. This number has been consistently growing since the early 2000s. In 2009, the federal, provincial, and territorial members of the Canadian Council on Geomatics (CCOG) recognized that consumers of GNSS corrections data had very little ability to verify that service providers were following best practices to ensure the quality of their work. It is common for surveyors to delineate property boundaries or to define the location of civil infrastructure with significant economic value, so being dependent upon another party without quality assurance was perceived as a major risk. Additionally, this new dependence upon commercial ACSs for GNSS corrections posed a threat to the consistency of position values in Canada. To address this concern, CCOG tasked its Canadian Geodetic Reference System Committee (CGRSC) with developing a plan to describe, validate, and provide certification of the GNSS corrections services consumed by industry. This paper summarizes the development of Natural Resources Canada’s (NRCan) Compliance Program for High Accuracy, GNSS Services, and how it can benefit professional surveyors across Canada.
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Hu, Jiahuan, Ding Yi, and Sunil Bisnath. "A Comprehensive Analysis of Smartphone GNSS Range Errors in Realistic Environments." Sensors 23, no. 3 (February 2, 2023): 1631. http://dx.doi.org/10.3390/s23031631.
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Precise positioning using smartphones has been a topic of interest especially after Google decided to provide raw GNSS measurement through their Android platform. Currently, the greatest limitations in precise positioning with smartphone Global Navigation Satellite System (GNSS) sensors are the quality and availability of satellite-to-smartphone ranging measurements. Many papers have assessed the quality of GNSS pseudorange and carrier-phase measurements in various environments. In addition, there is growing research in the inclusion of a priori information to model signal blockage, multipath, etc. In this contribution, numerical estimation of actual range errors in smartphone GNSS precise positioning in realistic environments is performed using a geodetic receiver as a reference. The range errors are analyzed under various environments and by placing smartphones on car dashboards and roofs. The distribution of range errors and their correlation to prefit residuals is studied in detail. In addition, a comparison of range errors between different constellations is provided, aiming to provide insight into the quantitative understanding of measurement behavior. This information can be used to further improve measurement quality control, and optimize stochastic modeling and position estimation processes.
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Li, Wei, Shengyu Kang, Yueqiang Sun, Weihua Bai, Yuhe Wang, and Hongqing Song. "A Machine Learning Approach for Air-Quality Forecast by Integrating GNSS Radio Occultation Observation and Weather Modeling." Atmosphere 14, no. 1 (December 28, 2022): 58. http://dx.doi.org/10.3390/atmos14010058.
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Air-quality monitoring and forecasting are crucial for atmosphere pollution control and management. We propose an innovative data-driven framework for air quality index (AQI) prediction by integrating GNSS radio occultation (GNSS-RO) observation and weather modeling. Empowered by the state-of-the-art machine learning approach, our method can effectively predict regional AQI with a comparable accuracy much more quickly than the traditional numerical modeling and simulation approach. In a real case study using a representative region of China, our data-driven approach achieves a 2000 times speedup; meanwhile, the prediction error measured by rRMSE is only 2.4%. We investigate further the effects of different models, hyperparameters, and meteorological factors on the performance of our AQI prediction framework, and reveal that wind field and atmospheric boundary-layer height are important influencing factors of AQI. This paper showcases a direct application of GNSS-RO observation in assisting in forecasting regional AQI. From a machine learning point of view, it provides a new way to leverage the unique merits of GNSS atmospheric remote sensing technology with the help of the more traditional weather forecasting modeling approach.
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YADAV, J. K. S., R. K. GIRI, and L. R. MEENA. "IPWV estimation and data quality analysis from different GNSS antenna." MAUSAM 63, no. 1 (December 31, 2021): 77–88. http://dx.doi.org/10.54302/mausam.v63i1.1458.
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Global Navigation Satellite System (GNSS) is widely used now days in variety of applications. The observation file for the near realtime estimation of Integrated Precipitable Water Vapour (IPWV) received at the ground-based receiver is mixed with ambiguities. Multi-path effects affect the positional accuracy as well as range from satellite to ground based receiver of the system. The designing of the antenna suppress the effect of multi-path, cycle slips, number of observations, and signal strength and data gaps within the data streams. This paper presents the preliminary data quality control findings of the Patch antenna (LeicaX1202), 3D Choke ring antenna (LeicaAR25 GNSS) and Trimble Zephyr antenna (TRM 39105.00). The results shows that choke ring antenna have least gaps in the data, cycle slips and multi-path effects along with improvement in IPWV. The signal strength and the number of observations are more in case of 3D choke ring antenna.
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Sadarviana, Vera, Brian Bramanto, Teguh P. Sidiq, Mohamad Gamal, Daniel A. Tampubolon, Rahmadi Hilmafizar, Reyhan A. Biantoro, Hana Alifiyanti, Muhammad T. A. Faruq, and Muhammad F. Muttaqin. "Stability Analysis of GNSS Control Point Network for Material Displacement Monitoring on the Slopes using Stability Monument Evaluation and Adjustment Data Processing Scheme: Preliminary Result." E3S Web of Conferences 94 (2019): 01023. http://dx.doi.org/10.1051/e3sconf/20199401023.
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The Global Navigation Satellite System (GNSS) has been used widely for hazards monitoring, such as landslide or material displacement on the slope due to its high accuracy and precision positioning. However, to assure its accuracy and precision, a further data quality and site assessment must be taken into account. In such a way, it is possible to determine whether the site monitoring is moved or not. Six location of GNSS observation points were established based on the geological structure and the terrain slopes. Satellite visibilities analysis, multipath analysis, and kinematic precise point positioning analysis were performed to assess the GNSS data quality and the monitoring stability. These procedures will determined the further processing scheme for each site monitoring. Some of areas experience the indication of cracks in road and building construction, which lead into an assumption of the displacement has been accumulated in a sub meter fraction. Thus, accounting all of those aspects, first adjustment data processing was implemented to achieve the preliminary results of the first observation.
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Scherbakov, V. V., A. P. Karpik, I. V. Scherbakov, M. N. Barsuk, and I. A. Buntsev. "Geodetic technologies for monitoring ballast compaction parameters during the construction and overhaul of railways using global navigation satellite system." Geodesy and Cartography 961, no. 7 (August 20, 2020): 8–13. http://dx.doi.org/10.22389/0016-7126-2020-961-7-8-13.
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The development of a monitoring system based on global satellite navigation systems (GNSS) of ballast compaction quality during the construction and overhaul of railways is covered in the article. Traditional geodetic methods for determining the quality of ballast compaction are tedious. Non-geodetic methods (dynamic control systems, empirical models and geophysical methods) are not widely used on railways due to the low reliability of the ballast compaction quality, as well as the high complexity of the work. The proposed method and device of a quality control system for ballast compaction are based on the measurement of draft and residual deformations during compaction in dynamic mode. The current coordinates are determined using GNSS with dual-antenna positioning receivers performing advanced functions, including determining the relative position of the antennas in plan and height. The monitoring system developed at the Siberian State University of Railway Engineering enables real-time determining parameters which characterize the quality of compaction with high accuracy and the ability of controlling the compaction process according to the current parameters.
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Wu, Zhilu, Yanxiong Liu, Yang Liu, Jungang Wang, Xiufeng He, Wenxue Xu, Maorong Ge, and Harald Schuh. "Validating HY-2A CMR precipitable water vapor using ground-based and shipborne GNSS observations." Atmospheric Measurement Techniques 13, no. 9 (September 18, 2020): 4963–72. http://dx.doi.org/10.5194/amt-13-4963-2020.
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Abstract. The calibration microwave radiometer (CMR) on board the Haiyang-2A (HY-2A) satellite provides wet tropospheric delay correction for altimetry data, which can also contribute to the understanding of climate system and weather processes. The ground-based global navigation satellite system (GNSS) provides precise precipitable water vapor (PWV) with high temporal resolution and could be used for calibration and monitoring of the CMR data, and shipborne GNSS provides accurate PWV over open oceans, which can be directly compared with uncontaminated CMR data. In this study, the HY-2A CMR water vapor product is validated using ground-based GNSS observations of 100 International GNSS Service (IGS) stations along the global coastline and 56 d shipborne GNSS observations over the Indian Ocean. The processing strategy for GNSS data and CMR data is discussed in detail. Special efforts were made in the quality control and reconstruction of contaminated CMR data. The validation result shows that HY-2A CMR PWV agrees well with ground-based GNSS PWV with 2.67 mm as the root mean square (rms) within 100 km. Geographically, the rms is 1.12 mm in the polar region and 2.78 mm elsewhere. The PWV agreement between HY-2A and shipborne GNSS shows a significant correlation with the distance between the ship and the satellite footprint, with an rms of 1.57 mm for the distance threshold of 100 km. Ground-based GNSS and shipborne GNSS agree with HY-2A CMR well.
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Rügamer, Alexander, Cécile Mongrédien, Santiago Urquijo, and Günter Rohmer. "Theoretical Analysis of Overlay GNSS Receiver Effects." International Journal of Embedded and Real-Time Communication Systems 3, no. 3 (July 2012): 38–53. http://dx.doi.org/10.4018/jertcs.2012070103.
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Having given a short overview of GNSS signals and state-of-the-art multi-band front-end architectures, this paper presents a novel contribution to efficient multi-band GNSS reception. A general overlay based front-end architecture is introduced that enables the joint reception of two signals broadcast in separate frequency bands, sharing just one common baseband stage. The consequences of this overlay are analyzed for both signal and noise components. Signal overlay is shown to have a negligible impact on signal quality. It is shown that the noise floor superposition results in non-negligible degradations. However, it is also demonstrated that these degradations can be minimized by judiciously setting the relative gain between the two signal paths. As an illustration, the analytical optimal path-control expression to combine overlaid signals in an ionospheric-free pseudorange is derived for both Cramér-Rao Lower Bound and practical code tracking parameters. Finally, some practical overlay receiver and path control aspects are discussed.
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Wang, Chunhang, Zhe An, Supalux Jairueng, Lakkana Ruekkasaem, M. Jayasudha, and Bhupesh Kumar Singh. "Model Optimization of Agricultural Machinery Information Control System Based on Artificial Intelligence." Journal of Food Quality 2022 (April 30, 2022): 1–7. http://dx.doi.org/10.1155/2022/7456650.
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Agricultural mechanization information in our country has the main problems existing in the management and utilization. The analysis of China’s agricultural mechanization management model and related software is presented based on combining modern science and technology as well as the development of agricultural mechanization management information system based on network software to standardize the management information collection, processing, storage and transmission, agricultural mechanization management information science, standardization, automation, etc. According to the analysis, the output target speed after fusion is more stable, and the stability is increased by 59.59% compared with the single-point GNSS velocity measurement data, and by 18.32% compared with the data measured by the binocular vision velocity measurement system. It has realized the goal of accurate speed measurement from low speed to high speed. In particular, it has solved the problems such as vehicles unable to complete positioning and vehicle skidding caused by trees blocking GNSS satellite signals during field operations.
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Huang, Shengxiang, Wen Zhang, and Gen Wu. "Research on Real-Time Supervisory System for Compaction Quality in Face Rockfill Dam Engineering." Journal of Sensors 2018 (2018): 1–11. http://dx.doi.org/10.1155/2018/6487405.
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Compaction quality control in filling construction is of great significance to the stability and durability of the face rockfill dam. The conventional method of quality control mainly relies on manual process control and inspection for a limited number of test holes, which cannot meet the high requirements of modern mechanized construction and schedule anymore, with increasing of scale of face rockfill dams. There is an urgent need to propose a new quality control method of face rockfill dams during the entire compaction process. In this paper, a supervisory system based on GNSS (Global Navigation Satellite System) technology, wireless data communication technology, Internet of things technology, and computer technology is developed to supervise the real-time roller compaction parameters of the working surface including rolling track, rolling times, rolling speed, thickness, and smoothness. The system obtains continuous and high-precision spatial position information of roller compaction machines through GNSS technology and then calculates the roller compaction parameter information. The compaction quality control for the face rockfill dam is achieved through the supervision of roller compaction parameters. The feasibility and robustness of the developed supervisory system are validated by a case study in the face rockfill dam of Shuibuya project in China. The practice shows that the system provides a new and effective method of process control for the construction quality of the roller compaction in dam engineering and realizes real-time, precision, and automatic supervising of roller compaction parameters and ensures better construction quality.
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Shcherbakov, Vladimir, Ivan Buntsev, and Olga Kovaleva. "Development of a control system for a ballast cleaning machine using GNSS." E3S Web of Conferences 135 (2019): 02003. http://dx.doi.org/10.1051/e3sconf/201913502003.
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Monitoring the geometric parameters of cutting and cleaning ballast during reconstruction and overhaul works is one of the most important tasks of ensuring high quality repair work. The paper describes a new type of automated control system to control the cutting process and the cleaning of ballast performed at major overhaul and reconstruction. This automated control system uses the data of a multisystem GNSS receiver, base Reference stations and spring-return mechanisms for installing antennas on the working body of the track machine (bar chain). Nowadays, gravel-cleaning machines have installed standard work quality control systems (depth of ballast cut and lateral slope), and other measuring control tools are also used. The disadvantages of existing technologies and instrumental testing are considered. The modern automatic control systems of various types developed by SGUPS and based on the use of global navigation systems are presented. Detailed schemes of working elements of ACS installed on the ballast cleaning machine (BCM) are presented. Algorithms to determine the depth and cross slope of the ballast cutting and control of these values are considered. The use and effectiveness of this type of ACS providing the required accuracy of work and continuous monitoring of the main quantities are substantiated.
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Santos, J., R. Teodoro, N. Mira, and V. B. Mendes. "GEOSPATIAL DATA QUALITY OF THE SERVIR CORS NETWORK." ISPRS Annals of Photogrammetry, Remote Sensing and Spatial Information Sciences II-3/W5 (August 20, 2015): 285–90. http://dx.doi.org/10.5194/isprsannals-ii-3-w5-285-2015.
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The SERVIR Continuous Operation Reference Stations (CORS) network was implemented in 2006 to facilitate land surveying with Global Navigation Satellite Systems (GNSS) positioning techniques. Nowadays, the network covers all Portuguese mainland. The SERVIR data is provided to many users, such as surveyors, universities (for education and research purposes) and companies that deal with geographic information. By middle 2012, there was a significant change in the network accessing paradigm, the most important of all being the increase in the responsibility of managing the network to guarantee a permanent availability and the highest quality of the geospatial data. In addition, the software that is used to manage the network and to compute the differential corrections was replaced by a new software package. These facts were decisive to perform the quality control of the SERVIR network and evaluate positional accuracy. In order to perform such quality control, a significant number of geodetic monuments spread throughout the country were chosen. Some of these monuments are located in the worst location regarding the network geometry in order to evaluate the accuracy of positions for the worst case scenarios. Data collection was carried out using different GNSS positioning modes and were compared against the benchmark positions that were determined using data acquired in static mode in 3-hour sessions. We conclude the geospatial data calculated and provided to the users community by the network is, within the surveying purposes, accurate, precise and fits the needs of those users.
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Fu, Wenju, Guanwen Huang, Yuanxi Zhang, Qin Zhang, Bobin Cui, Maorong Ge, and Harald Schuh. "Multi-GNSS Combined Precise Point Positioning Using Additional Observations with Opposite Weight for Real-Time Quality Control." Remote Sensing 11, no. 3 (February 4, 2019): 311. http://dx.doi.org/10.3390/rs11030311.
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The emergence of multiple global navigation satellite systems (multi-GNSS), including global positioning system (GPS), global navigation satellite system (GLONASS), Beidou navigation satellite system (BDS), and Galileo, brings not only great opportunities for real-time precise point positioning (PPP), but also challenges in quality control because of inevitable data anomalies. This research aims at achieving the real-time quality control of the multi-GNSS combined PPP using additional observations with opposite weight. A robust multiple-system combined PPP estimation is developed to simultaneously process observations from all the four GNSS systems as well as single, dual, or triple systems. The experiment indicates that the proposed quality control can effectively eliminate the influence of outliers on the single GPS and the multiple-system combined PPP. The analysis on the positioning accuracy and the convergence time of the proposed robust PPP is conducted based on one week’s data from 32 globally distributed stations. The positioning root mean square (RMS) error of the quad-system combined PPP is 1.2 cm, 1.0 cm, and 3.0 cm in the east, north, and upward components, respectively, with the improvements of 62.5%, 63.0%, and 55.2% compared to those of single GPS. The average convergence time of the quad-system combined PPP in the horizontal and vertical components is 12.8 min and 12.2 min, respectively, while it is 26.5 min and 23.7 min when only using single-GPS PPP. The positioning performance of the GPS, GLONASS, and BDS (GRC) combination and the GPS, GLONASS, and Galileo (GRE) combination is comparable to the GPS, GLONASS, BDS and Galileo (GRCE) combination and it is better than that of the GPS, BDS, and Galileo (GCE) combination. Compared to GPS, the improvements of the positioning accuracy of the GPS and GLONASS (GR) combination, the GPS and Galileo (GE) combination, the GPS and BDS (GC) combination in the east component are 53.1%, 43.8%, and 40.6%, respectively, while they are 55.6%, 48.1%, and 40.7% in the north component, and 47.8%, 40.3%, and 34.3% in the upward component.
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Anh, Tu Tran, Thuc Nguyen Van, and Huy Le Xuan. "Developing a network time server for LEO optical tracking." Bulletin of Electrical Engineering and Informatics 11, no. 3 (June 1, 2022): 1308–16. http://dx.doi.org/10.11591/eei.v11i3.3636.
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In 2021, to enhance the Vietnam's capability in space situational awareness, Vietnam national space center started to develop a space surveillance and tracking system using optical telescopes. An important part of the system is getting accurate timing to guarantee high quality astrometry measurements. A time server was self-developed to meet the demand. The device takes reference time from global navigation satellite system (GNSS) and synchronizes the time to all computers in the network using network time protocol (NTP). GNSS antenna, GNSS receiver module, and Raspberry Pi 4 were used to build a simple stratum 1 NTP time server. The device works smoothly, the synchronization is accurate and stable in both the server and the clients.
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Sertić, Hrvoje, Rinaldo Paar, Hrvoje Tomić, and Fabijan Ravlić. "Influence of Flight Height and Image Sensor on the Quality of the UAS Orthophotos for Cadastral Survey Purposes." Land 11, no. 8 (August 5, 2022): 1250. http://dx.doi.org/10.3390/land11081250.
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The possibility of using unmanned aircraft systems (UAS) for cadastral survey purposes was investigated in this research. A study site consisting of 26 ground control points (GCP) and checkpoints (CP) was established. The study site was first measured by the classical methods of geodetic surveying, i.e., by the polar method using a total station. After that, all points were additionally measured by the Global Navigation Satellite System (GNSS) Real-Time Kinematic (RTK) method. The GNSS RTK method was used to determine the coordinates of all points in the official map projection of Croatia, HTRS96/TM, while the polar method was used to increase the positional “strength” of points in all directions, i.e., to improve the relative accuracy between them. Using UASs with different image sensor characteristics, the study site was measured by an aerial photogrammetry method at different flight heights with the purpose of obtaining a high-quality digital orthophoto plan (DOF). The absolute orientation of the model was performed using the external orientation data of each digital image based on GNSS and Inertial Measurement Unit (IMU) UAS’s sensors, as well as using GCPs. Achieved precision of obtained DOF, as well as accuracy analysis of aerial photogrammetry was performed by considering the adjusted survey data collected by classical and GNSS RTK methods as true values and comparing them with the coordinates obtained by the aerial photogrammetry method from DOFs. Based on the achieved results and conclusions obtained from the study site, the second field test was performed above a small settlement which served as an area for cadastral survey using the UAS and GNSS RTK method. Again, precision and accuracy were determined, based on which we derived recommendations and conclusions for using UASs for cadastral survey purposes.
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Mattheuwsen, L., M. Bassier, and M. Vergauwen. "THEORETICAL ACCURACY PREDICTION AND VALIDATION OF LOW-END AND HIGH-END MOBILE MAPPING SYSTEM IN URBAN, RESIDENTIAL AND RURAL AREAS." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-2/W18 (November 29, 2019): 121–28. http://dx.doi.org/10.5194/isprs-archives-xlii-2-w18-121-2019.
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Abstract. Mobile mapping systems are increasingly being used for the acquisition of 3D information of the environment. Although these systems are very efficient in data capturing compared to more traditional methods, the high cost of high-end accurate mobile mapping systems is a major drawback. In contrast, the much cheaper low-end mobile mapping systems are more frequently used for less accurate projects where visualization is more important. In general, the achievable accuracy level is the driving factor that differentiates low-end from high-end systems. To determine this value, the sensor quality, calibration and GNSS reception quality should be reliably evaluated.In this paper, we present a theoretical accuracy model of a mobile mapping system that takes into account variable GNSS accuracy. The predicted accuracy level of low-end and high-end mobile mapping systems is evaluated in a comprehensive accuracy analysis. The absolute accuracy of the system is determined in three datasets in which GNSS reception quality varies between optimal, good and poor. Additionally, the relative accuracy of both systems is checked by comparison of control distances. The presented approach allows for a more general and robust accuracy prediction of mobile mapping systems in different circumstances.
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Gao, Ming, Genyou Liu, Shengliang Wang, Gongwei Xiao, Wenhao Zhao, and Dong Lv. "Research on Tightly Coupled Multi-Antenna GNSS/MEMS Single-Frequency Single-Epoch Attitude Determination in Urban Environment." Remote Sensing 13, no. 14 (July 9, 2021): 2710. http://dx.doi.org/10.3390/rs13142710.
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GNSS-only attitude determination is difficult to perform well in poor-satellite-tracking environments such as urban areas with high and dense buildings or trees. In addition, it is harder to resolve integer ambiguity in the case of single-frequency single-epoch process mode. In this contribution, a low-cost MEMS gyroscope is integrated with multi-antenna GNSS to improve the performance of the attitude determination. A new tightly coupled (TC) model is proposed, which uses a single filter to achieve the optimal estimation of attitude drift, gyro biases and ambiguities. In addition, a MEMS-Attitude-aided Quality-Control method (MAQC) for GNSS observations is designed to eliminate both the carrier multipath errors and half-cycle slips disturbing ambiguity resolution. Vehicle experiments show that in GNSS-friendly scenarios, the Ambiguity Resolution (AR) success rate of the proposed model with MAQC can reach 100%, and the accuracy of attitudes are (0.12, 0.2, 0.2) degrees for heading, pitch and roll angles, respectively. Even in harsh scenarios, the AR success rate increases from about 67% for the GNSS only case to above 90% after coupling GNSS tightly with MEMS, and it is further improved to about 98% with MAQC. Meanwhile, the accuracy and continuity of attitude determination are effectively guaranteed.
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Zhang, X., J. Zhang, L. Zhang, and J. Liu. "ANALYSIS OF COMMON QUALITY PROBLEMS IN COORDINATE TRANSFORMATION BETWEEN REFERENCE COORDINATE SYSTEM AND GEOCENTRIC COORDINATE SYSTEM." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-2/W13 (June 5, 2019): 1281–86. http://dx.doi.org/10.5194/isprs-archives-xlii-2-w13-1281-2019.
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<p><strong>Abstract.</strong> In the working of the existing reference coordinate system transformed into the coordinate system of the geocentric coordinate system, many experts and scholars have in-depth research on the transformation methods such as geodetic control point results (including GNSS base station coordinates, GNSS control point coordinates, triangle point coordinates), basic geographic information data results (including DLG, DOM, DEM, DRG, DSM, etc.) and other spatial information data. On the basis of these studies, many provinces and cities have completed the coordinate system transformation of surveying and mapping results in China. This paper expounds the method of transforming the existing reference coordinate system into the geocentric coordinate system, summarizes and sorts out the common quality problems in the process of different data and different methods, and analyses the causes of the problems and the impact on the transforming results. Based on the above work, The paper provides reference and suggestions for the transforming work, which is aimed to improve the transformation quality in the future.</p>
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Lee, Jae, Jae Lee, and Jung Kim. "New Quality Control Algorithm Based on GNSS Sensing Data for a Bridge Health Monitoring System." Sensors 16, no. 6 (May 27, 2016): 774. http://dx.doi.org/10.3390/s16060774.
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Li, Tao, Jinling Wang, and Denis Laurichesse. "Modeling and quality control for reliable precise point positioning integer ambiguity resolution with GNSS modernization." GPS Solutions 18, no. 3 (October 15, 2013): 429–42. http://dx.doi.org/10.1007/s10291-013-0342-8.
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Fu, Wenju, Guanwen Huang, Qin Zhang, Shengfeng Gu, Maorong Ge, and Harald Schuh. "Multi-GNSS real-time clock estimation using sequential least square adjustment with online quality control." Journal of Geodesy 93, no. 7 (November 22, 2018): 963–76. http://dx.doi.org/10.1007/s00190-018-1218-z.
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