Accurate Coordinates Research Articles

Positioning Accuracy Model of Sailing‐Circle GPS‐Acoustic Method

AbstractSailing‐circle GPS‐acoustic method, prevalently applied for measuring ocean floor crustal deformation, allows the precise positioning of an underwater transponder in a global frame. In the method, distance estimation requires prior information, such as transponder depth or incident angle. However, sometimes the prior information is inaccurate or absent. Under these circumstances, this study proposes two kinds of positioning methods that utilize an iteration composed of an inverse or direct ray tracing method and the least squares approach to constantly modify the initial data to obtain an accurate incident angle and coordinates of an underwater transponder. Even though an accurate incident angle can be got and there is no time delay or spatial‐temporal heterogeneities of SSP (sound speed profile), SSP density and geometric incident angle still influence ranging errors and PDOP (position dilution of precision) during distance intersection. In order to reduce the two kinds of impacts, this paper deduces a positioning error model based on the principle of sailing‐circle method. On the one hand, the proposed algorithms and model are verified by a simulated experiment for various SSP density, geometric incident angle, and transponder depth. On the other hand, in a practical experiment, average positioning accuracy of 0.025 m and vertical accuracy of −0.02 m are achieved, and the improved accuracy is about 85% higher than that of the ordinary sailing‐circle method.

Computational method for increasing the accuracy of determining coordinates

The article discusses a computing system for determining the location of an object by using satellite monitoring in real time with high accuracy. The computing system proposed by the authors is based on the determination of triple phase differences. High coordinate accuracy is ensured by entering additional data, such as tropospheric and ionospheric models. The resulting system is currently being tested.

Multi-frequency quadrifilar helix antennas for cm-accurate GNSS positioning

Abstract For a few years now, GNSS multi-frequency quadrifilar helix antennas (QHA) are available to be used for precise GNSS applications. We performed test measurements with two types of multi-frequency QHA and compared them with a geodetic patch antenna. Although code and carrier phase noise and high-frequent multipath was determined to be larger as compared to the geodetic antenna, the fast-static horizontal coordinate accuracies are on the same level and demonstrate cm-accuracy capability. One of the QHA types exhibited an increased susceptibility to near-field multipath effects which resulted in a degraded accuracy of the vertical coordinate component.

Аналіз середньоквадратичного відхилення апаратури “Кpoпивa”,“Укpoп”,“Artos” тa “Бaзaльт-М” вiднoснo кaтoлoгу кoopдинaт геoдезичниx пунктiв

The aim of the article is to present the results of global navigation satellite systems (GNSS) and geographic information systems (GIS) analysis in military units on the example of software and hardware system (computer appliance CA) “Kropyva”, “Ukrop”, “Artos” and “Basalt-M”, in particular comparison of coordinates determination accuracy by devices in relation to the catalog of geodetic points coordinates and the list of points coordinates of special geodetic networks. Method. The research was carried out on the basis of available literature sources analysis on this subject and practical application of CA “Kropyva”, “Ukrop”, “Artos” and “Basalt-M”, comparison of coordinates definition accuracy and development of recommendations on their basis. Experimental studies of coordinate determination with the help of software without obstacles that would interfere with the passage of satellite signal, and with obstacles, on the basis of which the conclusions are based. Results. Theoretical, methodical and practical problems of using CA “Kropyva”, “Ukrop”, “Artos” and “Basalt-M” in troops for coordinates determining have been studied. The tendencies and prospects of the studied CA are analyzed, taking into account the devices error in the coordinates determining and the expediency of their use for topographic and geodetic support of units. A thorough analysis of four tools for coordinates determining was compared and performed. The ways of satellite navigation systems application and geoinformation systems in military units are presented, on the example of CA “Kropyva”, “Ukrop”, “Artos” and “Basalt-M”. The main tasks are substantiated. Experimental researches of coordinates determining by different CA are carried out, different time intervals of comparisons the data with the catalog of geodetic points coordinates are received. Scientific novelty. The need for this study is due to the fact that although PJSC “Kropyva”, “Ukrop” and “Artos” are authorated for use in the Ukrainian Armed Forces, and “Basalt-M” is in service, or actively used in units, including the Area Joint Forces (JF) operations, but anyone did not performed comparison of coordinate accuracy and application recommendations. There are no scientific works in Ukraine that would relate to the coordinates determining accuracy of the devices in relation to the catalog of geodetic points coordinates of special geodetic boundaries. The main emphasis of the study is on the peculiarities of the use of CA. Their analysis and prospects in the military sphere are carried out. Practical meaning. Based on the analysis of “Kropyva”, “Ukrop”, “Artos” and “Basalt-M” aparatus standard deviation in relation to catalog of geodetic points coordinates, recommendations for the use of tactical level commanders have been developed. The temporal features of PAC application and their influence on the coordinate determinating accuracy are singled out. The CA which is most expedient to apply is established. The results of the study are designed for unit commanders who can use them for more effectively performing of their combat missions.

Performance Evaluation of Precise Point Positioning for BeiDou-3 B1c/B2a Signals in the Global Range.

With the construction and development of the BeiDou navigation satellite system (BDS), the precise point positioning (PPP) performance of the BDS is worthy of research. In this study, observational data from 17 stations around the world across 20 days are used to comprehensively evaluate the PPP performance of BDS B1c/B2a signals. For greater understanding, the results are also compared with the Global Positioning System (GPS) and BDS PPP performance of different signals and system combinations. The evaluation found root mean square (RMS) values of the static PPP in the north (N), east (E), and upward (U) components, based on the B1c/B2a frequency of BDS-3, to be 6.9 mm, 4.7 mm, and 26.6 mm, respectively. Similar to the static positioning, the RMS values of kinematic PPP in the three directions of N, E, and U are 2.6 cm, 6.0 cm, and 8.5 cm, respectively. Besides this, the static PPP of BDS-3 (B1cB2a) and BDS-2 + BDS-3 (B1IB3I) have obvious system bias. Compared with static PPP, kinematic PPP is more sensitive to the number of satellites, and the coordinate accuracy in three dimensions can be increased by 27% with the combination of GPS (L1L2) and BDS. Compared with BDS-2+BDS-3 (B1IB3I), the convergence time of BDS-3 (B1CB2a) performs better in both static and kinematic modes. The antenna model does not show a significant difference in terms of the effect of the convergence speed, though the number of satellites observed has a certain influence on the convergence time.

A Mathematical Formulation for Establishing the Relationship of Accuracy and Configuration of Data Acquisition in Close Range Photogrammetry. (Dept. C)

Configuration of data acquisition in close range photogrammetry is defined by (1) the base, which is the distance between the exposure stations of a stereopair, (2) the object distance, which is the perpendicular distance from the center (midfield) of object space to the base, and (3) the convergence of the two camera axes. The accuracy of object space coordinates of points is a function of configuration. A mathematical formulation establishing the relationship of accuracy and configuration is derived and then applied to obtain the optimum configuration, that gives the best accuracy in close range photogrammetry applications. The formulation developed is general and can be applied to calculate the expected accuracy of any given configuration, or to design a configuration that will yield a required accuracy.

Method for acquiring accurate coordinates of the source point in electron backscatter diffraction

An electron backscatter diffraction device is an important accessory for a scanning electron microscope and can provide crystal structure orientation and phase content data through analysis of electron backscatter diffraction patterns. The acquisition of these data depends on pattern indexing, including interplanar angle calculation and crystal plane indexation. The coordinates of the source point are key points for interplanar angle calculation, and they vary with the movement of the incident beam. In this study, we first combined the grey gradient calculation with screen moving method to achieve accurate positioning of source point and obtained coordinates of source point with sub-pixel precision. The errors of three coordinates were 0.07%, 0.06% and 0.04%, respectively. By using this coordinate of source point to conduct interplanar angle calculation the maximum error was 0.53°, which was a good proof of the accuracy of source point positioning. Then we established the relationship between source point coordinates variation and incident beam movement. Coordinates can be given out based on the displacement of beam directly. And to illustrate the accuracy, interplanar angle calculation was performed and the maximum error was 0.81°. This means that the relationship between variation of source point coordinates and beam movement is highly accurate.

Assessment of GPS/Galileo/BDS Precise Point Positioning with Ambiguity Resolution Using Products from Different Analysis Centers

Suffering from hardware phase biases originating from satellites and the receiver, precise point positioning (PPP) requires a long convergence time to reach centimeter coordinate accuracy, which is a major drawback of this technique and limits its application in time-critical applications. Ambiguity resolution (AR) is the key to a fast convergence time and a high-precision solution for PPP technology and PPP AR products are critical to implement PPP AR. Nowadays, various institutions provide PPP AR products in different forms with different strategies, which allow to enable PPP AR for Global Positioning System (GPS) and Galileo or BeiDou Navigation System (BDS). To give a full evaluation of PPP AR performance with various products, this work comprehensively investigates the positioning performance of GPS-only and multi-GNSS (Global Navigation Satellite System) combination PPP AR with the precise products from CNES, SGG, CODE, and PRIDE Lab using our in-house software. The positioning performance in terms of positioning accuracy, convergence time and fixing rate (FR) as well as time to first fix (TTFF), was assessed by static and kinematic PPP AR models. For GPS-only, combined GPS and Galileo PPP AR with different products, the positioning performances were all comparable with each other. Concretely, the static positioning errors can be reduced by 21.0% (to 0.46 cm), 52.5% (to 0.45 cm), 10.0% (to 1.33 cm) and 21.7% (to 0.33 cm), 47.4% (to 0.34 cm), 9.5% (to 1.16 cm) for GPS-only and GE combination in north, east, up component, respectively, while the reductions are 20.8% (to 1.13 cm), 42.9% (to 1.15 cm), 19.9% (to 3.4 cm) and 20.4% (to 0.72 cm), 44.1% (to 0.66 cm), 10.1% (to 2.44 cm) for kinematic PPP AR. Overall, the positioning performance with CODE products was superior to the others. Furthermore, multi-GNSS observations had significant improvements in PPP performance with float solutions and the TTFF as well as the FR of GPS PPP AR could be improved by adding observations from other GNSS. Additionally, we have released the source code for multi-GNSS PPP AR, anyone can freely access the code and example data from GitHub.

Research on Particle Swarm Practical Algorithm of Partial Differential Exact Solution Based on Computer Software Analysis

Particle swarm collaboration has many applications on the Internet. It is necessary to cluster a large number of algebraic matrices to obtain enough data. The current research focuses on the correlation between particle swarm coordination and matrix, and does not fully consider the difference between geometries. There is a large overlap, which leads to the same results for different matrices, leading to double counting problems. Therefore, based on the analysis of computer technology, this paper proposes a particle swarm optimization algorithm based on partial differential exact solutions. The selected geometric matrix has higher correlation and lower overlap. Experimental results show that this method can significantly improve the accuracy and efficiency of particle swarm coordination.

Knowledge-based self-calibration method of calibration phantom by and for accurate robot-based CT imaging systems

Modern X-ray imaging system with feature of low-dose and high spatial resolution imaging has become a prevalent noninvasive imaging technique in clinic. High-resolution imaging of cone-beam computed tomography (CBCT) system crucially relies on accurate geometric calibration. Accurate coordinates of bearing balls (BBs) on calibration phantom are essential prerequisites to precisely realize geometric calibration of CBCT systems. However, due to phantom-making error, BB position deviations may occur between the actual value and theoretical value, further resulting in estimation error of realistic parameters in geometric calibration. Current algorithms that can estimate BB coordinates are insufficient and not robust. In this study, we proposed a knowledge-based self-calibration method by means of a robot-based CT system to fill the vacancy. The moving knowledge from one single manipulator of dual manipulators is utilized for automatic self-calibration of the calibration phantom, which is then for accurate geometry calibration for the dual manipulator-based imaging system. Specifically, different projections of BBs can be obtained by moving the robotic manipulator, on which X-ray tube is installed several times, while the detector and the calibration phantom remain stationary. Hence, the actual BB coordinates can be estimated by minimizing two separate cost functions determined by reprojection errors and relocation errors of BBs. Simulation study shows that the mean of absolute distance values of the estimated coordinates are 0, 0.0164, and 0.0190 mm, and the standard deviation values of Gaussian noise are 0%, 10%, and 15% of a single pixel size on BB projection, respectively. Experiments demonstrate that the image quality of the reconstructed results has been improved to a large extent after utilizing the proposed self-calibration method. The performance is even superior to that of images acquired by performing geometric calibration on a high-precise calibration phantom with more BBs. The proposed method provides a flexible utility value to acquire high precision geometry and generate high-quality images for CBCT systems.

Accuracy and Uncertainty of Gradient Based Leak Localization Procedure for Liquid Transmission Pipelines.

This paper describes issues of leakage localization in liquid transmission pipelines. It focuses on the standard leak localization procedure, which is based on the calculation of pressure gradients using pressure measurements captured along a pipeline. The procedure was verified in terms of an accuracy and uncertainty assessment of the resultant coordinate of a leak spot. An important aim of the verification was to assess the effectiveness of the procedure in the case of localization of low intensity leakages with a level of 0.25–2.00% of the nominal flow rate. An uncertainty assessment was carried out according to the GUM convention. The assessment was based on the metrological characteristics of measuring devices and measurement data obtained from the laboratory model of the pipeline.

Correlation between the accuracy and speed of hand control in primary schoolchildren and the amount of screen time

Introduction. The means and methods of computerized learning introduced into the education system in recent years are changing the attitude towards writing with a pen. Children are increasingly typing on a keyboard. This brings into focus research investigations aimed at identifying the possible influence of the above-mentioned type of educational activity on the indicators of psychomotor skills. The purpose of this research is to study accuracy and speed indicators of psychomotor coordination when working with hands in primary school students, depending on the amount of computer load (screen time). Materials and Methods. The study involved 4205 primary schoolchildren in grades 1-4 from 66 educational settings in Moscow (5 academic years, testing took place in October and March-April; all samples were independent). Indicators of psychomotor coordination (speed, accuracy, and smoothness of movements) when performing a motor test using "computer movement meter" (CMM) device were evaluated. The amount of lesson and out-of-school screen time was evaluated by teachers, relying on the hygiene standards: 0 points – no load, 1 point – compliance with hygiene standards, 2 points – twice exceeding the standards, 3 points – exceeding the standards by 3 or more times. Statistical data processing was performed using nonparametric criteria. Results. The research revealed the correlation between the total (lesson and out-of-school) screen time and indicators of psychomotor coordination in primary schoolchildren. The most obvious differences in psychomotor indices were found at the very beginning of school education – in October, in the 1st grade: in children with a minimum amount of computer load, the indicators of speed and accuracy were the worst. Speed indicators of psychomotor skills in groups of children (especially boys) with a high computer load have seasonal variability in the form of improvement by the end of the school year. Accurate indicators of psychomotor skills, on the contrary, with an increase in the amount of general computer load, lose variability and decrease. The smoothness of movements did not depend on the screen time. Conclusions. The identified changes in the psychomotor skills of primary school students who are active computer-users can be considered as a positive adaptive response in the form of developing new motor skills.

Utilization of CBCT to improve the delivery accuracy of Gamma Knife radiosurgery with G-frame.

PurposeTo quantify the G‐frame based stereotactic coordinate definition accuracy of Leksell coordinate G‐frame‐based Gamma Knife radiosurgery (GKRS) by the on‐board cone‐beam CT (CBCT) and establish remedial action rules to minimize the delivery errors.MethodsWe analyzed the data of 108 patients (a total of 201 tumors) treated by GKRS with G‐frame for head fixation. After co‐registering the CBCT images and plan reference images, the Leksell GammaPlan (LGP) treatment planning system provided the amount of geometric translation and rotation required to minimize the position difference between the plan and treatment. The software also calculated maximum displacement, which characterizes the position shift more clearly. We studied how much these predicted dosimetric quantities changed if the treatment was delivered without correcting the patient's position.ResultsThe maximum displacement of the patient position obtained from the co‐registration of CBCT and plan reference images was 0.81 ± 0.38 mm (0.24–2.03 mm). The target coverage decreased by 3.3 ± 7.0% on average (−48.5% to +35.7%). The decrease of the target coverage, however, became smaller as the target volume increased. In particular, if the volume was greater than 2 cm3, the %change in target coverage was always less than −5%.ConclusionsThe position differences reported by the registration module of LGP were within the accuracy limit of image registration for most clinical cases, but the errors could be larger in some cases. Therefore, we propose the following decision process. We do not advise position adjustment for G‐frame based GKRS if the maximum displacement is less than 1 mm. When this limit is exceeded, however, another criterion should be applied to the decision making by considering the tumor size (or the treatment volume) together with the acceptable change of the tumor coverage.

ANALYSIS OF POSITIONING DEVIATION BETWEEN BEIDOU AND GPS BASED ON NATIONAL REFERENCE STATIONS IN CHINA

Abstract. In order to probe into the characteristics of positioning deviation between Beidou Navigation Satellite System (Beidou) and global positioning system (GPS), and investigate possible contribution of Beidou data to refinement of global coordinate system, refined calculation is made on observation data of 240 national reference stations that are distributed uniformly across China on the whole in this study. These stations support satellite signals of four global navigation satellite systems, including Beidou, GPS, GLONASS and Galileo, and a 5-year time span from 2016 to 2020 is adopted. In this study, PPP is calculated based on GPS data and Beidou single system data in no-difference resolution network mode, and accurate coordinates of national reference stations in two processing modes are obtained. Analysis of difference between the calculations based on Beidou data and on GPS data shows that the consistency between Beidou and GPS positioning results reaches about 5 mm in the east and in the north, and about 1.3 cm in the height direction.

Performance investigation of LAMBDA and bootstrapping methods for PPP narrow-lane ambiguity resolution

ABSTRACT Precise point positioning with ambiguity resolution (PPP-AR) is a powerful tool for geodetic and time-constrained applications that require high precision. The performance of PPP-AR highly depends on the reliability of the correct integer carrier-phase ambiguity estimation. In this study, the performance of narrow-lane ambiguity resolution of PPP using the Least-squares AMBiguity Decorrelation (LAMBDA) and bootstrapping methods is extensively investigated using real data from 55 IGS stations over one-month in 2020. Static PPP with 24-, 12-, 8-, 4-, 2-, 1- and ½-h sessions using two different cutoff angles (7° and 30°) was conducted with three PPP modes: i.e. ambiguity-float and two kinds of ambiguity-fixed PPP using the LAMBDA and bootstrapping methods for narrow-lane AR, respectively. The results show that the LAMBDA method can produce more reliable results for 2 hour and shorter observation sessions compared with the bootstrapping method using a 7° cutoff angle. For a 30° cutoff angle, the LAMBDA method outperforms the bootstrapping method for observation sessions of 4 h and less. For long observation times, the bootstrapping method produced much more accurate coordinates compared with the LAMBDA method without considering the wrong fixes cases. The results also show that occurrences of fixing the wrong integer ambiguities using the bootstrapping method are higher than that of the LAMBDA method.

Aggregated occurrence records of the invasive alien striped field mouse (Apodemus agrarius Pall.) in the former USSR

BackgroundOpen access to occurrence records of the most dangerous invasive species in a standardised format have important potential applications for ecological research and management, including the assessment of invasion risks, formulation of preventative and management plans in the context of global climate and land use changes in the short and long perspective. The striped field mouse (Apodemusagrarius Pallas, 1771) is a common species in the temperate latitudes of the Palaearctic. Due to land use and global climate changes, several waves of expansion of the range of this species have been observed or inferred. By intrusion into new regions, the striped field mouse has become an alien species there. Apodemusagrarius causes significant harm to agriculture and is one of the most important pests of grain crops. In tree nurseries, A.agrarius destroys seeds of valuable tree species and gnaws at the bark of saplings of broadleaf species and berry bushes. It is one of the most epidemiologically important rodents, involved in the circulation of the causative agents of haemorrhagic fever with renal syndrome (HFRS) and many other zoonotic infections. The foregoing allows us to classify the striped field mouse as a dangerous invasive alien species in the expanding part of the range. A lot of data accumulated for this species are of interest from both ecological and applied points of view. The accumulation and aggregation of data on the occurrence records of A.agrarius is relevant for the study of ecology, biogeography and construction of the spatial distribution and ecological niche models in the context of global climate change. We have created a dataset of 1603 occurrence records of this species, collected from 1936 to December 2020 by various zoologists, previously published or original. These records relate to a significant part of the striped field mouse’s range in Russia (1264 records) and neighbouring countries (339 records). The dataset shows the position of the northern and central parts of A.agrarius range, the disjunction of the range in Transbaikalia and isolated populations in the north of the range. The data were obtained in different formats from literature, indicating different degrees of accuracy of geographic coordinates and with several variations of the species' name. In the process of aggregating and fixing errors, we created a set of georeferenced occurrence records, adopted a controlled vocabulary, removed duplicates and standardised the format of records using unified data structure. We examined the dataset for inconsistencies with the taxonomic position of A.agrarius and removed the incorrect records. This paper presents the resulting dataset of A.agrarius occurrence records in the territory of Russia and neighbouring countries in a standardised format.New informationThis is a validated and comprehensive dataset of occurrence records of A.agrarius, including both our own observations and records from literature. This dataset is available for extension by other researchers using a standard format in accordance with Darwin Core standards. In different countries, there are a lot of occurrence records for the striped field mouse, but the overwhelming part of them is presented in separate literary sources, stored in the form of maps and in zoological collections. Prior to this project, such information was not available to a wide range of researchers and did not allow the use of these spatial data for further processing by modern methods of analysis, based on geographic information systems (GIS technologies). The created dataset combines species occurrence records of many Soviet zoologists who studied the distribution of the striped field mouse over a significant part of its recent range, in Russia and neighbouring countries (within the former USSR). The final set of records was created by combining the species occurrence records using a uniform data structure, checking geographic coordinates and removing duplicate and erroneous records. The dataset expands the available information on the spatial and temporal distribution of the dangerous invasive species in Russia and neighbouring countries of the former USSR (Estonia, Latvia, Lithuania, Belarus, Ukraine, Moldova, Georgia, Azerbaijan, Kazakhstan and Kyrgyzstan).

Semi-Automatic Approach for Forming and Processing Laser Sensing Data of Urban Truss

Abstract- There is imprecision in the stage of construction because of manual quality control in the construction procedures. Forming and processing point clouds image of as is truss part with its CAD data are researched to identify and repair the geometric discrepancies and imprecision. Approved suggested technique of processing building model was done. Instead of manual processing of the 3D models points. BPNN architecture give the best coordinates processing training. It is applied to optimize the points forming process between the input laser scanned coordinates of the as-built model with the output true CAD coordinates. RMSE in x, y, xy, z and space vector R of all processing tasks are computed acceptably.

The method of increasing the accuracy of coordinates of the contaminated area and water surfaces during environmental monitoring

One of the methods for increasing the accuracy of compiling pollution maps based on the results of air and ground monitoring of environmental monitoring of territories is considered. It has been substantiated that for the study of large areas it is advisable to install equipment for monitoring the state of the environment on aircraft. To improve the accuracy of determining coordinates in difficult conditions, it is proposed to use a quasi-differential mode of operation of navigation equipment placed on an aircraft in the developed method. The aircraft is equipped with various equipment and moves at high speed, conducting research on large areas of the territory. At an aircraft speed of more than 250 km / h, the accuracy of determining the coordinates of 30 m for drawing up an ecological map on a large scale suits the services responsible for environmental safety. Based on these data, additional environmental monitoring is carried out only in areas where pollution is detected. This reduces the time for complete environmental monitoring and saves material resources.

Microdisplacement Measurement Based on F-P Etalon: Processing Method and Experiments.

Herein, a processing method is proposed for accurate microdisplacement measurements from a 2D Fabry–Perot (F-P) fringe pattern. The core of the processing algorithm uses the F-P interference imaging concentric ring pattern to accurately calculate the centre coordinates of the concentric ring. The influencing factors of measurement were analysed, and the basic idea of data processing was provided. In particular, the coordinate rotation by the 45-degree method (CR) was improved; consequently, the virtual pixel interval was reduced by half, and the calculation accuracy of the circle centre coordinate was improved. Experiments were conducted to analyse the influence of the subdivision and circle fitting methods. The results show that the proposed secondary coordinate rotation (SCR) by 45 degrees method can obtain higher accuracy of the centre coordinate than the CR method, and that the multichord averaging method (MCAM) is more suitable for calculation of the centre coordinate than the circular regression method (CRM). Displacement measurement experiments were performed. The results show that the standard experimental deviation of the centre of the circle is approximately 0.009 µm, and the extended uncertainty of the displacement measurement in the range of 5 mm is approximately 0.03 μm. The data processing method studied in this study can be widely used in the field of F-P interferometry.

Sequential Ambiguity Resolution Method for Poorly-Observed GNSS Data

Integer ambiguity resolution is required to obtain precise coordinates for the global navigation satellite system (GNSS). Poorly observed data cause unfixed integer ambiguity and reduce the coordinate accuracy. Previous studies mostly used denoise filters and partial ambiguity resolution algorithms to address this problem. This study proposes a sequential ambiguity resolution method that includes a float solution substitution process and a double-difference (DD) iterative correction equation process. The float solution substitution process updates the initial float solution, while the DD iterative correction equation process is used to eliminate the residual biases. The satellite-selection experiment shows that the float solution substitution process is adequate to obtain a more accurate float solution. The iteration-correction experiment shows that the double-difference iterative correction equation process is feasible with an improvement in the ambiguity success rate from 28.4% to 96.2%. The superiority experiment shows significant improvement in the ambiguity success rate from 36.1% to 83.6% and a better baseline difference from about 0.1 m to 0.04 m. It is proved that the proposed sequential ambiguity resolution method can significantly optimize the results for poorly-observed GNSS data.