Analysis Of Positioning Accuracy Research Articles

Enhancing aerial image registration: outlier filtering through feature classification

In the context of feature-based image registration, the crucial task of outlier removal plays a pivotal role in achieving precise registration accuracy. This research introduces an innovative binary classifier founded on an adaptive approach for effectively identifying and eliminating outliers. The methodology begins with the utilization of the scale invariant feature transform (SIFT) to extract features from two images, initially matched using the Euclidian distance metrics. Subsequently, a classification procedure is executed to segregate the feature points into two categories: genuine matches (inliers) and spurious matches (outliers), which is accomplished through the brute-force matcher (BFM) technique. To enhance this process further, a novel classifier rooted in the random forest algorithm is introduced. This classifier is trained and tested using a comprehensive dataset curated for this study. The newly proposed classifier plays a pivotal role in attenuating the influence of outliers, ultimately leading to refined image registration process characterized by enhanced accuracy. The effectiveness of this outlier removal approach is assessed through a meticulous analysis of positional and classification accuracy. Additionally, we offer comparative insights by evaluating the performance of selected algorithm on our dataset.

Design of a 3D space early warning system for high precision positioning technology of Beidou and analysis of differential positioning accuracy

The Beidou satellite navigation system has achieved certain results in positioning accuracy, but due to factors such as system errors, its accuracy still does not fully meet the requirements of high-precision measurement. Therefore, this study proposes a design method for a three-dimensional space early warning system, aiming to combine the positioning function of the BeiDou satellite navigation system and differential positioning technology to improve positioning accuracy. By utilizing differential positioning technology, multiple reference stations are arranged around the receiving device, and the positioning information received by these stations is used for accuracy correction. This method can effectively offset errors such as atmospheric errors, clock errors, and multipath effects between receivers, making the obtained positioning results more accurate. Through the design and implementation of a three-dimensional space early warning system, positioning errors can be predicted and monitored, and abnormal positioning situations can be detected and corrected in a timely manner, thereby improving the overall reliability of positioning. The system designed in this article can effectively improve positioning accuracy, meet the requirements of modern measurement technology for positioning accuracy, and demonstrate the superiority of the system through experimental verification and differential positioning accuracy analysis.

Positioning Accuracy Analysis of Industrial Robots Based on Non-Probabilistic Time-Dependent Reliability

Positioning Accuracy Analysis of Industrial Robots Based on Non-Probabilistic Time-Dependent Reliability

TDOA positioning accuracy analysis based on time difference direction‐finding in distributed high‐frequency surface wave radar

AbstractIn the past few decades, the Time Difference of Arrival location technology in distributed high‐frequency surface wave radar has attracted wide attention due to its simple system, low cost, and higher positioning accuracy. Based on the time difference direction‐finding algorithm, this article presents new mathematical expressions of geometric dilution of precision in the Time Difference of Arrival positioning systems. The time difference direction‐finding reveals that the angle measurements are accurate for any length of baseline. Then the differences in geometric dilution of precision between the proposed algorithm and traditional method are analysed. Time difference direction‐finding algorithm can improve positioning accuracy without additional target information. Compared with the traditional method, the proposed algorithm can improve the positioning accuracy of partial observation areas under the same radar measurement system. The simulation results are presented to demonstrate the effectiveness of the proposed algorithm.

The Influence of the Movement Method on the Results of Machine Tool Positioning Accuracy Analysis

AbstractThe improvement of machine tools, and therefore, of industrial production, requires high accuracy of machining while adapting to the different dimensions of the workpieces and to the machines themselves. As a result, the improvement of testing procedures and the analysis of positioning accuracy results represent an important research task in modern manufacturing engineering. The paper presents the results of the research carried out with the aim of determining the influence of the choice of parameters for standardized testing of positioning accuracy on the measurement results with reference to the characteristics of the machines from the point of view of the size of the workspace and the machines themselves. In this way, it is possible to choose the appropriate test parameters of the machine tools depending on their geometrical characteristics and test conditions and within the existing standards.

Analysis of 5G Smart Communication Base Station Doppler-Smoothed Pseudorange Single-Point Geodesic Positioning Accuracy

With the continuous development of mobile communication and satellite navigation technologies, the positioning requirements of 5G smart communication base stations are becoming higher and higher. With the opening of GNSS raw observation data, research on the positioning of a 5G smart communication base station has become a research hotspot in the surveying and mapping disciplines. In this paper, based on the GNSS observation data of the 5G smart communication base station, the quality of the original GNSS observation data of the 5G smart communication base station is studied and analyzed. A method based on Doppler smoothing pseudorange solves the problem that the original pseudorange observation values of the 5G smart communication base station are noisy and prone to multipath errors due to the limitations of the base station chips and processes, which makes the traditional data processing methods unable to meet the demand for higher accuracy positioning. This method uses Doppler observations to smooth the pseudorange and determines the Doppler smoothing strategy and closure values to improve the data quality. The experimental data show that Doppler smoothing pseudorange can improve data quality and positioning accuracy by 67.9% in the E direction, 64.8% in the N direction, and 65.5% in the U direction. The future world will develop in the direction of intelligence, and the wireless network 5G technology used to support the construction of this intelligent system will become the core driver for the development of a leading intelligent society. 5G network signals have higher reliability and lower latency and can meet the specific needs of smart manufacturing, autonomous driving, and other industrial applications. This new base station product can meet the construction needs of future 5G base stations, adapt to the future intensive, miniaturized, intelligent station construction mode, and realize safe and fast station construction, providing the necessary hardware support for 5G network coverage.

LSTM-based short-term ionospheric TEC forecast model and positioning accuracy analysis

LSTM-based short-term ionospheric TEC forecast model and positioning accuracy analysis

ACCURACY ANALYSIS OF REAL-TIME OBJECT POSITIONING WITHOUT GCP FOR IMAGES FROM UAV OBLIQUE ULTRA-LONG FOCAL SMALL VIEW FIELD WHISKBROOM CAMERA SYSTEM

Abstract. Using images from UAV oblique ultra-long focal small view field whiskbroom camera (ULF-SVF-WC) system for object positioning and mapping is more difficult than conventional aerial photogrammetry, for the particularity of oblique ULF-SVF-WC imaging mode. Therefore, the precision and accuracy of its object positioning are also quite different from that of the conventional UAV photography. In this paper, we analysed the accuracy of real-time object positioning without ground control points (GCPs) for images from UAV oblique ULF-SVF-WC System. Firstly, we studied the imaging principles and characteristics of the oblique ULF-SVF-WC system. Then, we established the coordinate transformation relationship from the object point to the image point and constructed a strict imaging model for oblique ULF-SVF-WC image, which was used for real-time single-ray back-projection positioning assisted by DEM. Thirdly, we quantitatively analysed the distribution and variation of the oblique ULF-SVF-WC image single-ray back-projection errors in theory based on error propagation law and simulation data. Finally, we conducted the experiment of real oblique ULF-SVF-WC flight images for the actual positioning accuracy analysis. The experiment results showed that: the influence of system error on positioning generally conforms to the distribution and variation of theoretical precision, that is, the accuracy of scanning direction is much lower than that of the flight direction; while the accuracy of actual single-ray back-projection positioning is evidently lower than that of the theoretical analysis and there are obvious system errors in the positioning residuals. It indicates that the 6 external orientation elements calculated from POS data contains obvious system error whose influence is greater than random error and this should be eliminated in real-time single-ray back-projection for object positioning.

Comparative Analysis of the Horizontal Positional Accuracy of Google Earth and Bing Imageries of Samaru, Kaduna State Nigeria

Satellite imageries have in the recent past gained popularity in the areas of geo-informatics and geo-positioning because they provide global coverage and are cost-effective. Nevertheless, the use of these services poses questions on their spatial data quality in terms of positional reliability and accuracy, which have implications for their applicability. This study, therefore, analyzed the horizontal positional accuracy of satellite imageries (Google Earth and Bing) of Samaru in Kaduna state, Nigeria. The coordinates of 63 ground points (GPs) acquired with the Total Station instrument (Leica TCA 1201 M) were assessed against their corresponding points on the imageries using simple statistical accuracy metrics. The results revealed that the root mean square error (RMSE) of positions on the ground were significantly different from the RMSE of positions on the Google Earth and Bing imageries only in the Easting direction at the 95% significance level when p (2-tailed) = 0.000 [p < 0.05]. The study revealed that 50% and 70% of the Easting and Northing coordinates of the Google Earth imagery were related to the corresponding ground coordinates. In addition, 51% and 67% of the Easting and Northing coordinates of the Bing imagery were related to the corresponding ground coordinates. The results also showed that the Google Earth and Bing imageries had an overall positional accuracy of 6.09 m and 6.02 m, respectively, with the latter being more reliable in determining horizontal positions in the study area. The accuracy obtained was sufficient for navigation purposes and ground-based measurements that do not require very high accuracy. It was suggested, however, that a geometrical accuracy evaluation of similar or different imageries of the same study location or a more complex terrain should be undertaken to determine their reliability.

In‐orbit geometric calibration approach and positioning accuracy analysis for the Gaofen‐7 laser footprint camera

The Gaofen-7 (GF-7) satellite is China's first submeter high-resolution optical stereo-mapping satellite. The satellite is equipped with two area-array laser footprint cameras to capture the laser spots emitted by laser altimeters. To accurately identify and locate the geographical positions of laser spots, a stepwise geometric calibration method with ground laboratory information for high-resolution area-array camera is proposed in this paper. It includes the internal and external calibration. First, the initial values of the camera's internal parameters are determined based on the laboratory calibration results. Then, based on a high-precision reference ortho-image and a digital elevation model, the ground control points (GCPs) for multi-scene footprint images are obtained by image matching. Finally, the external and internal calibration methods for the laser footprint camera are implemented successively. The experimental results indicate that this method can restore geometric imaging relationships with high precision. After the internal and external calibration, the systematic residual error of the image point is eliminated, the remaining residual achieves 0.38 pixel, and the accuracy of direct positioning on the ground is better than 5.0 m, and the elevation accuracy is within 1.5 m.

Positioning Accuracy Determination of the Servo Axes for Grinding Wavy-Tilt-Dam Seals Using a Four-Axis Grinder.

The wavy-tilt-dam (WTD) seal is considered to be one of the ideal sealing patterns used in nuclear reactor coolant pumps (RCPs). Grinding such seals with a four-axis grinder had been proposed and six grinding implementation strategies were described in our previous studies. However, another important issue is to determine the positioning accuracy of each servo axis so that the high-precision moving components can be selected properly. In the present paper, the positioning accuracy analysis is carried out to seek a balance between the manufacturing cost and the accuracy requirements. First, a geometric model is established for investigating the error sensitivity of each axis and setting reasonable accuracy allocation of the four axes. Subsequently, the combined influence of all four axes is assessed based on multi-body system (MBS) theory and homogeneous transformation matrix (HTM). According to the results calculated, positioning errors of the X-axis, Z-axis, B-axis, and C-axis within ±10 μm, ±0.1 μm, ±1 arcsec and ±60 arcsec are acceptable, respectively. Meanwhile, the form error calculated of the ground wavy face is no more than 109.74 nm. It is indicated that the accuracy level of the moving components is achievable by modern manufacturing techniques. The present paper is expected to serve as a theoretical basis for the design and development of the four-axis grinder.

Quantitative analysis and benchmarking of positional accuracies of neutron strain scanners

Positional accuracy is an important parameter in residual stress investigations with neutron diffraction, considering that precise measurements of strains at the same localised position along a number of sample orientations are required, including investigations of complete complex shaped engineering components. This study reports the development of a standardised approach for quantitative analysis of positional accuracy on neutron strain scanners that builds on previous campaigns. The approach uses standardised sample sets with specific geometries that enable quantitative assessment of instrumental and sample alignment procedures and associated accuracies. This method has been implemented on four participating instruments: ENGIN-X (United Kingdom), MPISI (South Africa), SALSA (France) and STRESS-SPEC (Germany), to render results representative of monochromatic and time-of-flight strain scanners. The benchmarking results show comparable performance between the instruments with positional accuracies around 100 μm readily achieved. This standardised approach confirms the high positional precision attainable for non-destructive stress determination, to unequivocally benefit utilisation by academia and industry alike. It is envisaged that this common calibration protocol and reporting template that conforms to the newly developed Neutron Quality Label for Internal Stress Characterisation be adopted by other facilities to facilitate expansion of the supportive network.

Optical satellite sensor and positioning accuracy analysis for the Hongqi-1-H9 wide-range satellite in different terrains

The excellent performance of geometric positioning of a newly launched satellite will greatly broaden its application field. Launched on January 15, 2020, the Hongqi-1-H9 wide-range satellite is the largest sub-meter-level satellite worldwide and the first ton-level commercial remote sensing satellite in China, with a resolution of less than 1 m and a swath width of 136 km. This study was aimed at assessing the geometric positioning accuracy of this newly launched satellite considering three aspects, namely, the circle error accuracy, rational polynomial coefficient-based direct geometric positioning accuracy and ground control point-based absolute positioning accuracy under urban, plain, and mountainous areas, with different topographies. The results of the conducted experimental investigation indicated that the Hongqi-1-H9 satellite could exhibit a high positioning accuracy in planar and vertical directions for different terrains. In particular, for our experimental areas with a low topography and few surface structures, the geometric positioning accuracy of the Hongqi-1-H9 satellite imagery was less than 4m and 2 m in the planimetry and elevation directions, respectively. These characteristics can promote the application of the Hongqi-1-H9 satellite images in agricultural surveys, target detection, and land surveys, among other domains.

A New Method for Positional Accuracy Analysis in Georeferenced Satellite Images without Independent Ground Control Points

This paper introduces a new method to analyze the positional accuracy of georeferenced satellite images without the use of ground control points. Compared to the traditional method used to carry out this kind of analysis, our approach provides a semiautomatic way to obtain a larger number of control points that satisfy the requirements of current standards regarding the size of the set of sample points, the positional accuracy of such points, the distance between points, and the distribution of points in the sample. Our methodology exploits high quality orthoimages, such as those provided by the Aerial Orthography National Plan (PNOA)—developed by the Spanish National Geographic Institute—and has been tested on spatial data from Landsat 8. Our method works under the current international standard (ASPRS 2014) and exhibits similar performance than other well-known methods to analyze the positional accuracy of georeferenced images based on the use of independent ground control points. More specifically, the positional accuracy achieved for a Landsat 8 dataset evaluated by the traditional method is 5.22 ± 1.95 m, and when evaluated with the proposed method, it exhibits a typical accuracy of 5.76 ± 0.50 m. Our experimental results confirm that the method is equally effective and less expensive than other available methods to analyze the positional accuracy of satellite images.

Performance of Tightly Coupled Integration of GPS/BDS/MEMS-INS/Odometer for Real-Time High-Precision Vehicle Positioning in Urban Degraded and Denied Environment

Global Navigation Satellite System Real-Time Kinematic (GNSS-RTK) technology is widely used in vehicle navigation, but in complex environments such as urban high-rise street, wooded street, overpass, and tunnel, satellite signals are prone to attenuation or even unavailability. It brings great challenges to the continuous high-precision navigation. For this reason, a tightly coupled (TC) integration algorithm for GPS (Global Positioning System)/BDS (BeiDou Navigation Satellite System)/MEMS-INS (Micro-Electro-Mechanical System-Inertial Navigation System)/Odometer (GCIO) is proposed for vehicle navigation in complex urban environments. The accuracy improvement and ambiguity resolution (AR) performance are analysed in this research. First of all, the INS positioning error is constrained by fusion GPS/BDS (GC) and odometer; then, the predicted position information is used to aid GPS/BDS ambiguity resolution. In GNSS-denied environments, the odometer/INS integration is still carried out for continuous navigation. Real-time experiments are carried out in urban degraded and denied environments to validate the performance of the integrated system. In high-rise streets, the ambiguity fixing success rate of GCIO mode is 13.57% higher than that of GC mode. In the wooded street environment, the success rate has increased particularly significantly, by about 55 percent. The positioning accuracy analysis for open environment, high-rise street, wooded street, overpass, and tunnel is conducted. The experimental results show that in the above environment, the order of 0.1 m positioning accuracy can be achieved in the case of satellite outage for 1 minute, which can meet the positioning needs in most scenarios.

Single star Doppler passive positioning accuracy analysis and processing based on sea state sensor

Marine state information is important in many areas of research, e.g. marine monitoring, marine weather forecast and climate forewarning, and this information can be collected by ocean buoys. In the process of measurement, Doppler passive positioning is used to determine the position of the buoy. This paper aims to identify the factors that influence the buoy positioning accuracy. It is derived from the error formula that the positioning accuracy of the buoy is related to the relative position error between satellite and buoy, satellite orbit error, and frequency measurement error. In the simulation, satellite ephemeris data are generated, the iterative location algorithm is used to get the location of buoy, and noises are analyzed at last. We find that the relative position and frequency measurement error have a significant impact on the positioning accuracy of the buoy. Therefore, in order to improve the buoy positioning accuracy, it is necessary to select a satellite position that is near the radiation source but not directly above it. Improving the frequency measurement accuracy will also greatly enhance the positioning accuracy.

Estimation of Dynamic MLC Parameters Using Dynamic MLC Position Accuracy Analysis Software in Prostate IMRT

It is necessary to verify an intensity-modulated radiation therapy (IMRT) plan and to confirm dose error within the tolerance, in order to perform it securely and precisely. IMRT with dynamic multi-leaf collimator (DMLC) requires high DMLC position accuracy. The DMLC position accuracy analysis software DynaLog File Viewer (DFV; Varian Medical Systems, Palo Alto, CA, USA) is used to analyze position errors of DMLC for IMRT plans. We analyzed correlation between DMLC parameters and position error of DMLC obtained from DFV in prostate IMRT. A regression analysis of the position error and the DMLC parameters was performed. As a result, a strong correlation was found between MLC position error and each of the DMLC parameters: leaf speed, gap width, and segment monitor unit (MU). We found the factors for the DMLC position error in this study. DMLC position error could be estimated from leaf speed, gap width, and segment MU when we analyze IMRT cases in the further study.

Three-dimensional positional accuracy analysis of uav imagery using ground control points acquired from multisource geospatial data

Three-dimensional positional accuracy analysis of uav imagery using ground control points acquired from multisource geospatial data

The comparison of VMAT test results for Clinac 2300C/D and TrueBeam accelerators

Volumetric Modulated Radiotherapy (VMAT) implementation requires additional Quality Assurance (QA) tests to assure stable machine performance especially in terms of dynamic parameters synchronization. The lack of a twin machine for TrueBeam led us to the investigation of backup workflow with Clinacs 2300C/D. These Clinacs were upgraded to make them VMAT-enabled. This study aimed to compare long-term VMAT performance QA on 3 accelerators: TrueBeam (TB) and 2 Clinacs (V4 and V5). All VMAT test plans were provided by Varian. The test set consisted of initial and advanced tests. Initial tests were intended to check the gravity effect on Multileaf Collimator (MLC) and dosimetry system. As the results of these tests were correct and there was visual inspection applied for MLC positioning accuracy analysis, they were not presented in the paper. We focused on 2 advanced tests: dose rate vs gantry speed and dose rate vs MLC speed. The idea of the advanced test was to compare segments irradiated with the same fluence but different dose rate, gantry speed or MLC speed. Test sets were irradiated weekly on average for 12 months. These tests were analysed following Varian procedures and criteria using in-house-developed software. Apart from that we calculated correlation between all segments pairs and performed profile analysis. According to Varian criteria, all tests for TrueBeam were very well within the tolerances. Dose rate vs gantry speed tests for Clinacs were within allowed limits while as many as 28% and 6% of dose rate vs MLC speed tests failed for Clinacs V4 and V5, respectively. The profile analysis revealed tests for which the difference between measured and planned dose was over 3% and still met the criteria. The correlation analysis showed that VMAT plans on TrueBeam were irradiated repeatably because all segments were strongly correlated. There was no correlation between the segment with the highest MLC speed and the other segments on Clinacs in dose rate vs MLC speed test. This segment was irradiated randomly. TrueBeam is more reliable than upgraded Clinacs 2300C/D for VMAT performance. That is why in our centre the one of upgraded Clinac that performed tests better served only as a backup machine for VMAT technique, and the second one was excluded from clinical use for this technique.

Analysis of signal strength, satellite visibility, position accuracy and ionospheric TEC estimation of IRNSS

The Indian Regional Navigation Satellite System (IRNSS) is an indigenously developed satellite navigation system to meet practical needs. The system, comprising a constellation of seven satellites in GEO orbit, has been fully operational since 2018. It is essential to evaluate the performance of the IRNSS continuously for various applications. As a part of ISRO field trial and data collection program an IRNSS Standard Positioning Service User Receiver (UR) placed at ACS College of Engineering (ACSCE), Bangalore, for independent field trial and data collection. The receiver is operational on a $24\times 7$ basis. A MATLAB Graphical User Interface has been developed to analyze and plot the data variation of signal strength, elevation angle, visibility of satellites, user position, position error, geometric dilution of precision (GDOP) and find the availability of the number of satellites plotted for every second based on the received data. From the results, it is observed that the signal strength (C/No) is good, i.e. above 40 dBHz, visibility of satellites at receiver location is good. The mean position at user location is found to be $X=1349700~\mbox{m}$, $Y = 6070902~\mbox{m}$, $Z = 1413860~\mbox{m}$ and latitude of 12.8914 degree, longitude of 77.465 degree and altitude of 739 m. The mean position from IRNSS is compared with Google map results showing a good match. The geometry distance of receiver location with respect to Earth center is estimated and observed. The RMS of position error for L1, L5 and dual frequency (L5+S) at ACSCE, Bangalore, is 9.7444 m, 6.6873 m and 5.6667 m, respectively. Hence, as expected the dual-frequency (L5+S) receiver gives an accurate position rather than the single-frequency signals. The IRNSS TEC is measured using Ionospheric group delay and the pseudo-range of L5 and S band which is collected from ACSCE receiver. A third order Savitzky-Golay-Filtered technique is used for TEC smoothing. RMSE between IRNSS TEC from pseudo-range and GPS TEC is 0.6482 TECU and the correlation coefficient is 0.9981. RMSE between IRNSS TEC from ionospheric delay of L5/S and GPS TEC is 1.971 TECU and the correlation coefficient is 0.9966. Finally, smoothed TEC values derived from pseudo-range measurements give a good result and can be used to generate daily TEC maps. In order to analyze the performance of IRNSS over the Indian region, we have chosen three other receiver stations located at Osmania University (Hyderabad), University of Burdwan (Bardhaman, West Bengal) and Shri Mata Vaishno Devi University (Katra, Jammu and Kashmir). Based on the results, we conclude that the IRNSS constellation is performing well and providing good signals for accurate user position determination and ionospheric data analysis.