

b 
Email: Peter Collier 
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Survey Review 53, No 380. September/October 2021 1. Land reallocation model with simulated annealing algorithm Land consolidation project has many stages. Land reallocation is the most considerable stage in which many factors play a role and forms the basis of this project. In this study, a new optimisationbased reallocation model has been developed to realise block reallocation by evaluating the requests of landowners. The reallocation according to the developed method also reset the block spaces automatically. The most powerful aspect of the method is that while the reallocation phase in land consolidation projects takes weeks and months, this method can be done in minutes. This method contributes to projects in terms of time and cost. Further information:
2. Horizontal coordinates transformation and residuals modelling on the territory of the Republic of Srpska The paper describes the model for coordinate transformation between ETRS89 and old reference system in the Republic of Srpska. The Helmert’s parameters were estimated, based on a set of 1741 points. The average magnitude of residuals was 0.3 m per coordinate and they were homogeneous at the local level. The basic model was complemented by a corrections grid that uses bilinear interpolation. The accuracy of the transformed horizontal positions obtained by this model is about 10 cm. In this way, a link between the two reference systems has been established on the overall territory of the Republic of Srpska. Further information:
3. Validation of GNSS baseline observation models using information criteria This paper adapts and discusses the information criterion (IC) approach for the validation of baseline GNSS observation models in the context of outliers. Three IC methods are compared with the conventional procedure of iterative data snooping (IDS). To verify the reliability of the two considered approaches, several scenarios differing in: the magnitude and number of outliers, and the interval between measurement epochs were investigated. Generally, the IDS procedure achieved the highest rates of correct model specification when no outlier existed. However, as the number of outliers was increasing one of the IC methods was starting to achieve the highest rates. Further information:
4. Optimising 2parameter Lambert Conformal Conic projections for groundtogrid distortions A Lambert Conformal Conic (LCC) projection with two truescale parallels of latitudes ϕl and ϕu can be recast in a LCC projection with one standard parallel of latitude ϕ0 and scale k0, having the practical advantage that the same type of definition can be used for the two conformal projections universally used: LCC and Transverse Mercator (TM). While equations giving ϕ0 and k0 in terms ϕl and ϕu can be found in the literature, inverse relationships are not readily found. They are derived in the present paper. These may be necessary in views of the planned future definition of the United States State Plane Coordinate System (SPCS) 2022 for the users of particular mapping software requiring to specify the two latitude values instead of the central latitude and central scale. While map projection parameters are customary selected to minimise ellipsoidtogrid distortions for a region, in some cases it could be more convenient to study and minimise groundtogrid distortions. Also bearing in mind the design of SPCS 2022, we discuss the advantages and disadvantages of working with each type of distortion definition. Further information:
5. A constrained extended Kalman filter based on LSVCE formulated by condition equations with prediction of crosscovariances A constrained extended Kalman filter (CEKF) based on leastsquares variance component estimation (LSVCE) is generally developed by condition equations since the proper prediction of dispersion matrices is one of the main bottlenecks in the KF algorithms. Here we investigate four problems which have not been simultaneously considered yet. These problems are examination of nonlinearty of dynamic model, VCE, general nonlinear state constraints and fairly general stochastic model. Although a few contributions proposed some adaptive KF in particular based on Helmert’s VCE method, they developed their filters for special problems with some restrictive conditions such as independence of all variables and/or linearity of the dynamic model. Also some of these filters did not apply VCE methods to all parts of the dynamic model. In this contribution, we try to overcome all of these restrictions. Moreover, LSVCE method gives some added advantages over other VCE methods. First the new formulation of CEKF is developed by condition equations with prediction of all possible crosscovariances as algorithm 1. Then the LSVCE method is applied to it after some modifications which results in an adaptive constrained extended Kalman filter (ACEKF) as the second algorithm. Further information:
6. A copula approach for sea level anomaly prediction: a case study for the Black Sea Forecasting future sea levels is of great importance in terms of the conservation of coastal areas, monitoring and forecasting coastal ecosystems, and the maintenance and planning of coastal structures. In addition, highly accurate sea level forecasts allow adequate water management policies and coastal infrastructures to be developed. Today, many methods, such as harmonic analyses, artificial neural networks and support vector machines, are used to predict sea level anomalies. In this study, a novel approach based on Copula functions is presented for the prediction of sea level anomalies. The primary purpose of this study is to examine the applicability and capability of Copulabased prediction models in predicting shortterm variations in the sea level. The minimum 95% correlations and minimum 22 mm RMSE values in sea level anomaly predictions during the testing period indicate that the Copula approach can be a powerful tool in the prediction of sea level anomalies. Further information:
7. Results from the first strapdown airborne gravimetry campaign over the Lake District of Turkey The first productionoriented strapdown airborne gravimetry in Turkey was carried out during fall 2019 over the Turkish Lake District. Comparisons at the large amounts of crossover points yield RMSE values below 1 mGal level, and the external comparison with the latest highresolution global geopotential model (GGM) shows a mean bias of around 1.1 mGal where the largest deviations are observed on the areas that could not be resolved by the GGM. The incorporation of new airborne data into the gravity field computations is supposed to reduce the errors stem from the data voids and enhance the maps for better interpretations. Further information:
8. An iterated reweighting total least squares algorithm formulated by standard leastsquares theory If both the coefficient matrix and the observation vector are affected by noise, a total leastsquares algorithm should be applied to obtain the solution. However, if they are also contaminated by outliers, the solution of the algorithm will seriously deviate from the true values. Therefore, the effect of outliers needs to be eliminated. For this purpose, the robust estimation is introduced into the total leastsquares algorithm, developing a new robust weighted total leastsquares algorithm. Simultaneously, considering the robustness of structure space, the standardized residuals are utilized to construct the weight function. Finally, the robustness and efficiency of this algorithm are verified by three experiments involving linefitting and 2D affine transformation. Further information:
9. Indoor space as the basis for modelling of buildings in a 3D Cadastre This paper presents a 3D cadastral data model for buildings. A review of the relevant research shows that a common concept in the 3D cadastre domain is using the legal building unit, i.e. real property unit, as the core modelling unit. Alternatively, this study proposes using indoor space as a core modelling unit. The main reason is to enable the efficient integration of cadastral data with the data from other domains. On the conceptual level, the model is linked to the Land Administration Domain Model (LADM). The integration options are studied for three international standards: IFC, CityGML and IndoorGML. Further information:
Survey Review 53, No 379. July/August 2021 1. A correlational inferencebased unscented total Kalman filter for integrated navigation An unscented total Kalman filter (UTKF) estimator with nonlinear dynamic errorsinvariables (DEIV) model is derived based on correlational inference. The proposed UTKF considers all random errors in both system and observation equations and is a Jacobian matrix free alternative to the existing TKF estimators. In particular, this estimator is applied to the inertial navigation system (INS)/ultrawideband (UWB) integration, in which the marginalised unscented transformation (MUT) as well as the use of generalised Rodrigues parameter (GRP) for attitude updates are embedded into the UTKF to improve the computational efficiency and deal with the dimensional mismatching problems. Furthermore, a theoretical analysis to the effects of DEIV model on total Kalman filter is given. Simulation test has been conducted to compare the performance of UTKF and standard unscented Kalman filter (UKF) in terms of attitude, velocity and position errors. The results demonstrate the feasibility and effectiveness of the proposed estimator. Further information:
2. An adaptive filtering algorithm of multilevel resolution point cloud The existing filtering methods for airborne LiDAR point cloud have low accuracy. An adaptive filtering algorithm is proposed which is improved based on multilevel resolution algorithm. First double index structure of Octree and KDtree is established. Then the initial reference surface is constructed by ground seed points. According to the slope fluctuation situation, the grid resolution of the ground referential surface is adjusted in an adaptive way. Finally, the refined surface is formed gradually by multilevel renewing resolution to provide filtered point cloud with high accuracy. Experimental results show that the error of Type II can be effectively reduced, the average Kappa coefficient increases by 0.53% and the average total error decreases by 0.44% compared with multiresolution hierarchical classification algorithm. The result tested by practically measured data shows that Kappa coefficient can reach 90%. Especially, it maintains advantages of high accuracy under complex topographic environment. Further information:
3. Design and development 3D RRR model for Turkish cadastral system using international standards The concepts of threedimensional cadastre (3D) and property ownership led to increased interest in land use management and research towards the end of the 90s. Within the scope of these studies, international standards and definitions have been realised. In Turkey, there are some academic studies available. However, there are not many studies conducted on an institutional basis. Turkey cadastre carried out by the General Directorate of Land Registry, and Cadastre (GDLRC) are kept. In this context, a 3D RRR (Right, Restriction and Responsibility) for Turkeybased cadastral data model design and development is essential in terms of not constitute a base for the study. The fact that these studies are in the context of LADM and ISO standards and OGC is very important in terms of the fact that the cadastral system is related to international standards. Further information:
4. Improved wavelet neural network based on change rate to predict satellite clock bias To develop a highaccuracy method for predicting SCB based on the analysis of the shortcomings of the wavelet neural network (WNN) model, an improved WNN model to predict SCB is proposed herein. The activation function of the WNN is constructed by combining the advantages of Shannon and Gauss ‘window’ functions to improve the WNN. Finally, the improved WNN model is used to predict SCB. The results show that the proposed model has the highest prediction accuracy, stability, and robustness. Moreover, it effectively predicts longtime SCB data. Therefore, the proposed model can predict SCB with high accuracy. Further information:
5. Cadastral updating: the case of Turkey Turkey has produced cadastral data using different methods until today. Therefore, not all the data are the same standard in quality. Three different methods (correction, digitisation and updating) have been applying for update. Choosing the right method will save significant time and cost. Also, surveying the fixed boundaries will give the most accurate results. However, this is not always possible. The distribution of fixed boundaries is only 46.39% in the application area. So, fixed boundaries should be measured as far as possible. The places where the digitisation and updating methods will be applied should be determined very well. Further information:
6. Implementing a mass valuation application on interoperable land valuation data model designed as an extension of the national GDI The main purpose of this study is to propose an interoperable land valuation data model for residential properties as an extension of the national geographic data infrastructure (GDI) and to make mass valuation process applicable with the use of machine learning approach. As an example, random forest (RF) ensemble algorithm was implemented in Pendik district of Istanbul to evaluate the prediction performance by using thematic datasets compatible with the data model. This study provides a methodology for various urban applications and robustness of the algorithm increases the prediction of the real estate values with the use of qualified datasets. Further information:
7. Estimation of parameters of probability integral method model based on improved fireworks algorithm How to accurately estimate the probability integral parameters based on the measured data has always been a difficult point in the application of the probability integral method. This paper introduced FWA into the solution of the probability integral method for the first time. Based on the analysis of strengths and weaknesses of FWA, IFWA (improved fireworks algorithm) was proposed. Then, the IFWAbased inversion model for probability integral parameters (MIFWA) was constructed by the fusion the mining subsidence law and probability integral method. Experiments show that MIFWA has better performance in antierrors of the observation and the geological mining generalization. Further information:
Survey Review 53, No 378. May/June 2021 1. Increasing efficiency of the robust deformation analysis methods using genetic algorithm and generalised particle swarm optimisation The paper analyses the possibility of increasing efficiency of the Iterative Weighted Similarity Transformation (IWST) method, which is a prototype of classic robust methods, using global optimisation approach instead of classical one, available in the literature. For the purpose of solving the optimisation problem of the IWST method, in addition to the Iterative Reweighted Least Squares (IRLS) method, the Genetic algorithm (GA) and Generalised Particle Swarm Optimisation (GPSO) algorithm were applied, in order to overcome some flaws of IRLS method. Experimental research was performed based on the Monte Carlo simulation using the mean success rate (MSR) on the example of the geodetic control network for monitoring the Šelevrenac dam in the Republic of Serbia. By using the GA and GPSO algorithms, the overall efficiency of the IWST method has been increased by about 18% compared to the IRLS method. Also, it has been determined that the efficiency of the IRLS method significantly reduces with the increase in the number of displaced potential reference points (PRPs), while the GA and GPSO algorithms’ efficiency does not change significantly. The values of overall absolute true errors due to the increased number of displaced PRPs in the GA and GPSO algorithms did not change notably while with the IRLS method their values increased significantly. Further information:
2. Impact of observation sampling rate on MultiGNSS static PPP performance The main objective of this study is to investigate the impact of observation sampling rate on the PPP performance, in terms of positioning accuracy and convergence time, under different multiGNSS combinations. For this purpose, daily observation datasets collected at ten IGSMGEX (International GNSS ServiceMultiGNSS Experiment) stations during the 1week period of January 612, 2019 with 1s, 5s,15s, and 30s sampling rates were processed under three different PPP processing modes, namely GPSonly, GPS/GLONASS and multiGNSS. The results indicate that the use of highrate observation sampling improves the PPP performance for all processing modes significantly. The contribution of increasing sampling rate, both for positioning error and convergence time, is more prominent in shorter periods, especially within the first 30 min for all processing modes. Finally, the multiGNSS processing mode with the 1s observation sampling rate has the best PPP performance and offers a considerable prospect for the GNSS applications. Further information:
3. Quality evaluation of linear inequality constrained estimation by Monte Carlo sampling in parameter space Existing approaches that describe the quality of inequality constrained estimates are not sufficient to meet the demands of inequality constrained leastsquare problems. We reconstruct the existing Monte Carlo method by converting the sampling space from observation space to parameter space, and propose a workflow to improve the computational efficiency. The proposed method is verified by a straightline fitting example with independent and dependent inequality constraints, and the constraints have different intensities. The results show that the proposed workflow has higher computational efficiency than the existing workflow and that the saved time is almost linearly related to the intensity of the inequality constraints. Further information:
4. Bias in leastsquares adjustment of implicit functional models To evaluate the benefit of a measurement procedure onto the estimated parameters, the dispersion of the parameters is usually used. To draw objective conclusions, unbiased or at least almost unbiased estimates are required. In geodesy, most of the functional relations are nonlinear but the statistical properties of the estimates are usually obtained by a linearised substituteproblem. Since the statistical properties of linear models cannot be passed to the nonlinear case, the estimates are biased. In this contribution, the bias of the parameters as well as the bias of the dispersion in nonlinear implicit models is investigated, using a secondorder Taylor expansion. Nonlinear implicit models are general models and are used, for instance, in the framework of surfacefitting or coordinate transformation, which considers errors for the coordinates in source and target system. The bias is introduced as a further indicator to validate the benefit of an adapted measurement process using more precise measuring instruments. Since some parametrisations yield an illposed problem, also the case of a singular equation system is investigated. To demonstrate the secondorder effect onto the estimates, a bestfitting plane is adjusted under varying configurations. Such a configuration is recommended in evaluating uncertainties of optical 3D measuring systems, e.g. in the framework of the VDI/VDE 2634 guideline. The estimated bias is used as an indicator whether a large number of poor observations provides better results than a small but precise sample. Further information:
5. Efficient point cloud corrections for mobile monitoring applications using road/railside infrastructure Light Detection and Ranging (LiDAR) systems are known to capture high density and accuracy data much more efficiently than other surveying methods. Therefore they are used for many applications, e.g. mobile mapping and surveying, 3D modelling, hazard detection, etc. However, while the accuracy of the laser measurements is very high, the accuracy of the resulting 3D point cloud is greatly affected by the georeferencing accuracy. This is especially problematic for mobile laser scanning systems, where the LiDAR is installed on a moving platform, e.g. a vehicle, and the point cloud is georeferenced by the data provided by a navigation system. Owing to the complexity of the surrounding environments and external conditions, the accuracy of the navigation system varies and thereby changes the quality of the point cloud. Conventional methods for correcting the point cloud accuracy either rely heavily on manual work or semiautomatic registration methods. While they can provide georeferencing under different conditions, each has their own problems. This paper presents a semiautomated georeferencing trajectory correction method by extracting features from the preprocessed point cloud and integrating this information to reprocess the navigation trajectory which is then able to produce better quality point clouds. The method deals with the changing errors within a point cloud dataset, and reducing the trajectory error from metre level to decimetre level, improving the accuracy by at least 56%. The accuracy of the regenerated point cloud then becomes suitable for many accuracydemanding monitoring and change detection applications. Further information:
6. An institutional analysis of land readjustment in Turkey Land readjustment is a property formation process which rearranges the geometries of cadastral parcels and immovable property rights thereof in accordance with land use plans. The literature presents several studies which analyze the effectiveness of land readjustment in various countries. This article aims to contribute to the existing work by presenting an analysis for the Turkish case study based on the Institutional Analysis and Development Framework developed by Elinor Ostrom. For this purpose, the organizational procedures and institutional arrangements that frame land readjustment in Turkey are examined. This analysis reveals the areas of possible reform that may facilitate a transparent and accountable, participatory and inclusive, fair and costeffective development of land. Further information:
7. Estimators of covariance matrices in Msplit(q) estimation This paper proposes methods for the determination of covariance matrices of Msplit(q) estimators. The solutions presented here allow Msplit(q) estimation to be supplemented by the operations from the domain of accuracy analysis (especially that concerning estimators of parameters). Theoretical forms of covariance matrices of Msplit(q) estimators were established using the empirical influence functions and the equivalent covariance matrices of observation errors. The estimators of covariance matrices of Msplit(q) estimators were determined based on the adopted statistical observation models and their random errors. The unknown variance coefficients of these models were estimated employing the principles of square estimation. Further information:
8. Velocity estimation performance of GNSS online services (APPS and AUSPOS) Before now, the various studies that have been undertaken to investigate the positioning performance of GNSS Online Services have been limited with regard to both time and number of sessions. Within the scope of this study, the accuracy of the velocity models estimated by APPS and AUSPOS are analysed using a wider period. Local ISKI CORS Network stations are used as the subject. To generate true values for an accurate comparison, 129 sessions with BERNESE (v5.2) software were conducted between 2008 and 2019. A linear trend was determined by using leastsquares adjustment to obtain true velocity values. To test the reliability of the true velocity values, seasonal, semiannual and annual oscillation movements have been examined. Additionally, the coherence of the velocity model with the sample data and compliance with the tectonic plate has been investigated. For GNSS Online Services, 34 sessions were carried out over the same timescale, and the velocity model was estimated. A Ztest with a 0.05 significance level was used to examine the performance of APPS and AUSPOS velocity values. As a result, the estimated true velocity model shows high compliance with sample data and the tectonic plate; no seasonal, semiannual or annual oscillation movements were identified. According to the study’s statistical test, the velocity model of APPS solutions performs slightly better than that of AUSPOS. However, both services show high performance in the velocity determination. In summary, the usability of GNSS Online Services in determining velocity has been shown with this study. Further information:
Survey Review 53, No 377. March/April 2021 1. A practical method for calculating reliable integer float estimator in GNSS precise positioning To overcome the problem that a fixed estimator is contaminated by a system error for the ambiguity be misjudged in the GNSS precise positioning, a reliable integer float estimator is recommended. Accordingly, the method for determining a finite number of integer vectors based on a given reliability probability is proposed, the formula for calculating the variance matrix of the recommended estimator is derived, and the judgment method of the estimator’s availability is proposed. The detailed process and the effect of the method are also demonstrated using examples to facilitate user application. Further information:
2. Objectbased geographical data model for determination of the cemetery sites using SWOT and AHP integration While in the times of feudalism the land was a source of wealth, having only a financial value, today it has become valuable as a limited resource. It should not be forgotten land is becoming scarce, so it must be very well planned and managed. In order for cemeteries to be sustainable and effectively manageable, it is essential to collect, store and examine information related to these sites like other types of areas. A geographic database design was developed in order to identify and resolve existing problems related to cemetery management nationwide in accordance with the ISO 19152 standard. Further information:
3. Receiver DCB analysis and calibration in geomagnetic stormtime using IGS products Solar activity and geomagnetic storm cause ionospheric disturbance and affect the GNSS positioning accuracy, which this effect cannot be ignored. The reliability depends mainly on differential code bias (DCB), when estimating the total electron content (TEC) with GNSS pseudorange observations. This study analyzes the variation characteristics of receiver DCB (RDCB) during a strong geomagnetic storm to determine whether the RDCB estimation is affected by space weather. Results show that the RDCB dispersion of lowlatitude stations is larger than that of other areas. On the storm day, the RDCB standard deviation (STD) exhibits a peak characteristic and the number of RDCB abnormal stations is significantly more than that on quiet day. Analysis shows that the RDCB abnormality is caused by the ionospheric model misalignment during the ionospheric disturbance. By correcting the RDCB, the RDCB STD is reduced by 43.10%. Thus, the model correction can improve the estimation accuracy of RDCB during geomagnetic storm. Further information:
4. Calibration of CCD sensors mounted on geodetic measuring systems If the eyepiece of a total station is replaced with a CCD sensor, the most important task is to calibrate the instrument. Calibration establishes a connection between the readings on the horizontal and vertical circles of the total station and the readings in the coordinate system of the CCD sensor. Our calibration method uses a collimator in a few meters distance, which serves as a target at infinity during the calibration. We tested the calibration using a QDaedalus astrogeodetic measuring system. The optimal number of calibration measurements, the optimal raster size, and the temperature dependence of the measurements were investigated. Further information:
5. A featurepreserving point cloud denoising algorithm for LiDARderived DEM construction To attenuate positional errors of LiDARderived datasets for constructing digital elevation models (DEMs), a featurepreserving point denoising algorithm (FPDA) is developed in this paper. FPDA includes three main steps: surface normal estimation, normal filtering and point position update. Numerical tests with two simulated surfaces indicate that FPDA is always more accurate than kriging and natural neighbour. Furthermore, FPDA has a high effectiveness of preserving feature lines. Realworld examples of interpolating LiDAR samples demonstrate that FPDA can best retain both prominent and subtle terrain features, while faithfully removing errors in mountainous and flat regions. Moreover, it outperforms some wellknown interpolation methods. Further information:
6. Equivalence properties of 3D conformal transformations and their application to reverse transformations Sevenparameter conformal coordinate transformations, also known as Helmert transformations, can be constructed in more than one way. Two possible orderings of the rotations are in common use, giving rise to Helmert versions 1 and 2. It is demonstrated how the rotation parameters of either version can be converted into the rotation parameters of the other. This is useful when software is designed for the other version. It also enables computation of the sameformula inverse transformation by changing the sign of the equivalent ‘other version’ parameters. These results were primarily intended for conformal transformations between geodetic datums. They can, however, be extended to coordinate transformations in disciplines such as photogrammetry where rotations sometimes exceed 90 degrees. Further information:
7. A highly adaptable method for GNSS cycle slip detection and repair based on Kalman filter The cycle slip detection and repair are crucial steps in the preprocessing of GNSS carrier phase observation. Currently, however, there are few cycle slip detection and repair methods that can meet the data processing needs for diverse situations. To solve this problem, a highly adaptable cycle slip detection and repair method is proposed. First, a cycle slip detection equation is established using the pseudorange and carrier doubledifferenced (DD) observations; the state equation is developed based on the satelliteground distance. Then, a Kalman filter estimation model is established by joining the two equations. Subsequently, the cycle slip can be detected and repaired. Finally, the state parameters are refined in accordance with the conditional distribution. According to the results of the example, all the simulated cycle slips are detected and repaired by the method proposed. It shows that the method can meet the data processing needs for multiple situations. Further information:
8. A review of universal hydrographic data model The Universal Hydrographic Data Model is a new generation of marine geographic information data model, referred to as S100 standard. In addition to supporting Electronic Navigational Charts (ENC) production, S100 can be used as a Geographic Information System standard to model all maritime objects. Therefore, it is necessary to carry out a comprehensive study on S100. In this review, we begin with a succinct overview of the history and development of S100. Then we discussed the problems of S100 and the corresponding solutions. Finally, some research directions of S100 are proposed to provide reference for future research and application. Further information:
Survey Review 53, No 376. January/February 2021 1. Urban land speculation; failure of land market This article is intended to examine the nature of urban expansion and development from a land speculation and urban sprawl perspective. Survey and case study approach were used to achieve this aim. As urban territory extends into adjacent periurban areas, speculators keep their land out of the current market so that developers of land and buildings must bypass it and home buyers should travel further distance to buy new lands and houses. This extra distance creates additional costs by increasing the cost of development, operation and travel. The finding of this article concludes that the speculators who held their land out off the market and received an average land value increase of about $230 per m2 each year generated extra social costs which they did not pay about $1,810 per m2 each year. Further information:
2. Derivation of rigorouslyconformal 7parameter 3D geodetic datum transformations This paper proposes a new method of deriving rigorouslyconformal 7parameter 3D coordinate transformations between geodetic datums. The problem of linearisation is reduced by distance analysis which provides an estimate of scalechange. The resulting 6parameter transformation is linearised to enable an initial leastsquares estimate of the rotation parameters. The 6parameter transformation is then relinearised to obtain a leastsquares estimate of the corrections to the rotations. The validity of the scalechange estimate can be tested and is verified in almost all cases. The exception is transformations covering very small areas where short distances maximise the impact of measurement errors in the control data. Even there, the method can be adapted to optimise the transformation. The method can also be used to obtain pseudooptimal conformal transformations that provide a closest fit to published BursaWolf transformations. Further information:
3. GPS + Galileo + QZSS + BDS tightly combined singleepoch singlefrequency RTK positioning The multiGNSS fusion makes positioning more reliable and accurate. Considering the signal difference of different systems, GPS + Galileo + QZSS + BDS tightly combined doubledifference model (TCDDM), including function and stochastic model, is proposed. The proposed model fully utilizes the overlapping frequency signals of various systems, and thus to enhance positioning model when DISBs are known beforehand. The observations of 3 ultrashort (1~10 m) and 3 short (4~10 km) baselines were processed by selfprogramming software, and the singleepoch singlefrequency RTK performance using different systemcombined models was evaluated by ambiguityfixed correctness rate (ACR) and positioning accuracy. It demonstrated that three and foursystem TCDDM were superior to their corresponding loosely combined doubledifference model (LCDDM) for ACR and positioning accuracy especially at high cutoff elevation. Moreover, foursystem TCDDM had the best RTK performance obtaining average ACRs of 100% and 97.6% even at 25° cutoff elevation for ultrashort and short baseline, respectively. Further information:
4. Single point positioning using full and fractional pseudorange measurements from GPS and BDS In conventional global navigation satellite system (GNSS) receivers, full pseudorange measurements are usually required to complete a single point position fix, which takes longer time than obtaining fractional pseudorange measurements. In order to shorten the time to first fix and improve the position accuracy during cold or warm start of a dualconstellation GNSS receiver, we propose a positioning algorithm using at least four full pseudorange measurements from one constellation and fractional measurements from either or both constellations. Theoretical rapid position results can be obtained with an identical accuracy to that of the conventional method using full measurements. Tests with simulated and real Global Positioning System (GPS) and BeiDou Navigation Satellite System (BDS) data validate the performance of the proposed approach. Further information:
5. Determination of the under water position of objects by reflectorless total stations When surveying through a water surface, a distortion of several centimetres caused by the refraction and the change in the velocity of the electromagnetic waves can be observed. Therefore, neither the position nor the height of an underwater point (object), which can be seen from above the water surface, is correctly measured. The authors want to point out the magnitude of geometric errors when measuring to points under water as well as the computation of correct under water positions of points from measurement through a water layer. A practical experiment was performed for a water depth of 0.16 m. Further information:
6. Global gravity models and the Ghanaian Vertical Datum: challenges of a proper definition This paper analyzes errors in satellite gravity and GPS/trigonometric benchmarks (BMs) in relation to defining the Ghanaian Vertical Datum (GhVD). Results indicate that synthesized gravity introduce approximately 5 mm of error to corrected heights. However, large errors in BMs render them unsuitable for applications, including properly defining the GhVD. Overall, normalorthometric corrections were of the order of a few millimetres, with comparatively larger Helmert orthometric and normal corrections. Accordingly, the most suitable heights for the GhVD are the normalorthometric heights, with the geopotential of the Helmert orthometric heights, 62636861.534±2.27 m2 s−2, suggested as the potential of the GhVD. Further information:
7. Application of baseline constraint Kalman filter to BeiDou precise point positioning This paper proposes a baseline constrained PPP method to enhance the performance. The approach is based on constrained Kalman filter, and applied to BeiDou PPP in static, pseudokinematic, real kinematic modes. Both zero baseline and short baseline constrained PPP are verified in static mode, while a marine geodesy environment is designed to evaluate the performance in kinematic mode. The experiment results show that, compared to the PPP without constraint, the baseline constrained PPP can significantly improve the positional accuracy. Furthermore, the accuracy of baseline constrained static PPP can reach centimetre level, while the kinematic PPP can reach decimetre level. Further information:
8. Evaluating success factors in the land readjustment applications: a case study of Trabzon Province, Turkey Land Readjustment plans (LR) provide tools for taking control of land development and construction, while organising social, cultural and technical infrastructure. In Turkey, LR applications, Pursuant to Law No. 3194, enable the creation of regular planned urban developments. The success of LR applications involves a comprehensive knowledge about the rules and relationships of the legal and community aspects of society. In this context, LR applications must be addressed and analysed by considering the success factors. In this study, LR application process was analysed to determine a set of quantitative factors in the Trabzon Province in Turkey. Cadastral and LR plans were reviewed to determine the success factors. By determining the quantitative factors: the correct regulation limits, an appropriate change in position of the parcel, the accuracy of the Development Readjustment Share account, the correctness of Public Partnership Share interruptions and the construction of the appropriate parcels, the success of LR applications were tested for pilot sites and comparisons were made with graphics. Further information:
9. The determination of the true geometrical form of Great Ephesus theater, Turkey by using field surveys The current deals with the determination of the ‘true’ geometrical shape of the Great theatre of Ephesus, which is the largest theatre in Asia Minor. To detect the geometrical form of the theatre a precise point dataset was created using terrestrial measurements performed directly on the theatre site. The wellknown ellipse and circle fitting algorithms were presented for detecting the precise geometrical shape of the amphitheatre rings. The study reveals that ellipse geometry fits well to the theatre arcs that is amphitheatre rings are generally elliptical in shape. The precise metric values of the parameters of the geometrical shape were computed to characterise theatre features. Further information:
10. Variations of precipitable water vapor using GNSS CORS in Thailand This research aims to analyze variation in a time series of Precipitable Water Vapor (PWV time series) using data at 11 widelydistributed Continuously Operating Reference Stations (CORS) in Thailand. In this paper, the PWV time series is estimated based on data from 2007 to 2015, used to monitor trends and seasonal variations. Significant annual variations of PWV are found at all GNSS stations, with amplitude from 6 to 19 kg/m2. The variations between the annual amplitudes of PWV in the South and near the ocean coasts are generally smaller than in the inland regions. The phase shift of annual PWV variation is about −0.43 (around July, rainy season). The comparison of PWV and 24hour cumulative rainfall data showed that the rainy season (running from around midMay to the end of October) exhibits the slightest swing, and the highest average amount of PWV. These results are consistent with the 24hour cumulative rainfall data. Further information:


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