Showing papers in "Survey Review in 2014"

Iterative algorithm for weighted total least squares adjustment

Abstract: In this contribution, an iterative algorithm is developed for parameter estimation in a nonlinear measurement error model y2e5(A2EA)x, which is based on the complete description of the variance–covariance matrices of the observation errors e and of the coefficient matrix errors EA without any restriction, e.g. in the case that there are correlations among observations. This paper derives the weighted total least squares solution without applying Lagrange multipliers in a straightforward manner. The algorithm is simple in the concept, easy in the implementation, and fast in the convergence. The final exact solution can be achieved through iteration. Based on the similarity between the proposed algorithm and the ordinary least squares method, the estimate for the covariance matrix of the unknown parameters can be analogously computed by using the error propagation law. The efficacy of the proposed WTLS algorithm is demonstrated by solving three WTLS problems, i.e. a linear regression model, a planar similarity transformation and twodimensional affine transformation in the case of diagonal and fully populated covariance matrices in both start and transformed coordinate systems.

Performance evaluation of short to long term GPS, GLONASS and GPS/GLONASS post-processed PPP

Abstract: In recent years, in addition to the GPS constellation, the ability to utilise extra satellites available in the GLONASS system enhanced the capabilities and possible applications of precise point positioning (PPP) method. However, the intrinsic differences between GPS and GLONASS and the lack of a fully tested global tracking network of multi-GNSS systems necessitate the evaluation of their combined use. This paper offers a comprehensive statistical assessment of static PPP using GPS-only, GLONASS-only and GPS/GLONASS combined data. Data analysis is performed in a short (hourly to daily) and a long (several weeks) term, spanning observations from eleven IGS stations. Evaluation of the results reveals insignificant differences in the accuracy and repeatability among the three satellite constellation solutions for long (8 h, 24 h) observation times. The superiority of the combined GPS/GLONASS solution is apparent for short (1 h, 2 h) observation periods, whereas analysis confirms the stability of PP...

Algorithm for purposes of determining real estate markets efficiency with help of land administration system

Abstract: The real estate market (REM) concerns many difficult and complicated issues. The subject of interest is the specificity of market and the processes taking place in its plane. The complexity and heterogeneity of real estate, the multitude of actors and their behaviours and finally various factors of efficiency and effectiveness of the real estate market, all create many difficulties in analysing and describing it. In this context, it is important to build a comprehensive real estate information system (land administration system, LAS), which will provide the relevant information, acting as a decision support system. LAS functioning properly will allow spatial and statistical analysis, archiving and also data visualisation. The main goal of this article is a proposed algorithm determining the efficiency of real estate markets with help of LAS, using rough sets.

3D+time Cadastre, possibility of implementation in Poland

Abstract: This paper presents a transition method from a 2D cadastre to a 3D+time system, using the available software, based on the official spatial data registers. For over two decades in Poland the official registers of terrain related objects have been undergoing modernisation. This modernisation focuses on the safety and protection of the rights to properties, increasing the efficiency of databases and the quality of data, as well as increasing the efficiency of planning and land management. The advanced technologies, such as CAD, GIS or DBMS, make it possible to build a digital terrain model (DTM) followed by a visualisation of surface objects, such as parcel boundaries or building outlines, in 3D. Modern relational databases and CAD tools also allow reconstruction of real estate state from any moment in history, registered in the database.

Robust Total Least Squares with reweighting iteration for three-dimensional similarity transformation

Abstract: To resist the influence of gross errors in observations on the adjusted parameters, the robust Least Squares (LS) adjustment has been extensively studied and successfully applied in the real applications. However, in the LS adjustment, the design matrix is treated as non-random even if its elements come from the real observations that are in general inevitably error-contaminated. Such assumption will lead to the incorrect solution if the gross error exists in the observations of design matrix. In this paper, we study the robust Total Least Squares (TLS) adjustment, where observation errors in design matrix are taken into account. The reweighting iteration robust scheme is applied to detect and identify the blundered observation equations as well as reweight them, obtaining the reliable TLS solution. The example of three-dimensional similarity coordinate transformation is carried out to demonstrate the performance of the presented robust TLS. The result shows that the robust TLS can indeed resist t...

GPS-structural health monitoring of a long span bridge using neural network adaptive filter

Abstract: The movement of bridge deck bearings plays a significant role in the safety of bridges. Real time kinematic global positioning system (GPS) continuous health monitoring using relative deformations was carried out on a long span Zhujiang Huangpu Bridge. The neural network aided adaptive filter is used to predict and adjust the GPS monitoring data. The statistical moments in time and frequency domains were used to analyse the movement of the bridge deck. The results indicate that (1) the proposed neural network with the adaptive filter model can be used to de-noise the GPS health monitoring signals, (2) the GPS is highly sensitive for bridge deck movements, (3) the statistical moments can be used to detect the movements and errors of the GPS observations, and (4) the bridge is very safe under different loads.

Comparison of two unconventional methods of estimation applied to determine network point displacement

Abstract: This paper presents two unconventional methods of estimation which can be applied to determine point displacement. The first one belongs to the class of R-estimation and it is a variant of the Hodges–Lehmann estimates (HLE); the second one belongs to the class of Msplit – estimates, and it is denoted as Shift-Msplit estimate. Both estimates are designed to assess the shift between two samples (or between two vectors of the parameters). Thus, they both are natural estimates of displacement of control network points while testing network deformation. The paper focuses on the comparison of the estimates’ accuracies and their robustness against outliers. The comparison is based on Monte Carlo simulations which seem to be the best method for this purpose and it is carried out for an example levelling network.

Triple carrier precise point positioning (PPP) using GPS L5

Abstract: The latest generation of GPS satellites, block IIF, include for the first time a new civil signal on L5 frequency (1176·45 MHz), in addition to the legacy signals on L1 (1575·42 MHz) and L2 (1227·60 MHz). Traditional precise point positioning (PPP) is based on L1/L2 dual-frequency observations to remove the ionospheric delay. However, L5 presents interesting properties, such as more robustness against interference compared to L2, which makes it suitable for critical applications. Therefore, navigation users can already start making use of the L5 signal, to increase reliability and redundancy for the most demanding applications. This article addresses the integration of the new L5 pseudorange and carrier phase observables in PPP, which at the same time allows to perform efficient signal characterisation. In particular, ionosphere-free combinations including L5 are explored and their corresponding observation equations introduced. Practical results using IGS MGEX observation data are presented.

Accuracy of single receiver static GNSS measurements under conditions of limited satellite availability

Abstract: At least two simultaneously operating receivers are required for differential global navigation satellite system (GNSS) positioning. In this mode, the systematic errors between stations can be estimated or reduced in order to achieve much higher accuracy. Precise point positioning (PPP) is a rather new category. PPP is a combination of the original absolute positioning concept and differential positioning techniques. In PPP we use observation data of a single receiver and additional information on individual GNSS errors derived from a GNSS network, usually from ground based augmentation systems (GBAS). GBAS systems can be divided by the area of operation into global, continental, national or regional ground support systems (e.g. ASG-EUPOS, CORS, SAPOS, SWEPOS). GBAS systems allow users with a single receiver to position in differential mode based on observations from the reference stations. This paper presents an analysis of the position determination accuracy using single receiver GNSS measurements condu...

3D cadastres: legal approaches and necessary reforms

Abstract: The increased number of amenities in modern societies involves the intense exploitation of land above and below the earth’s surface, resulting in complex constructions and proprietary status. Therefore, each country’s legal and cadastral framework needs to be amended in order to cope with the emerging conditions. This paper aims to summarise the regulations that define the creation of multi-surface property units in Common and Civil Law jurisdictions, in order to aggregate the legal instruments used in each one. Civil Law jurisdictions are influenced by the Roman principles which impose the right of accession and allow vertical ownership for the owner of the surface parcel. Common Law jurisdictions do not strictly relate ownership of immovable property to the ownership of the surface parcel. Significant research has been conducted in many countries which ended up either in specialised legal and cadastral reforms introducing property forms, such as condominium schemes, housing companies and limited rights ...

Assessment of the global digital elevation models ASTER and SRTM in Greece

Abstract: This study evaluates the height accuracy of the free to download global digital elevation models (DEMs): advanced spaceborne thermal emission and reflection radiometer (ASTER) global digital elevation model (GDEM) and shuttle radar topography mission (SRTM) for the area of Greece. The analysis is done in two ways; using control points with known elevation and accurate DEMs. Quantitative and qualitative assessments are made both for the whole country, and for specific regions (test sites). Using the DEMs of SRTM with coverage from 56u St o 60uN and ASTER GDEM with coverage from 83u St o 83uN, the elevation information is available to users free of charge almost worldwide. In the regions where both data sets exist, the question arises which one is best to use; the decision is based on a series of parameters, such as accuracy, homogeneity, reliability, completeness, performance of morphological features, as well as the purpose of the work for which the elevation information will be used. These parameters are reviewed and analysed using data covering Greece. The data come from various providers and varying formats. The evaluation of the results highlights the need for a ‘fit for purpose’ use of each of these DEMs, taking into consideration the implementation constraints (technical and qualitative specifications of each project), along with the usefulness of these DEMs for a wide range of applications.

Integration of D-InSAR technology and PSO-SVR algorithm for time series monitoring and dynamic prediction of coal mining subsidence

Abstract: Subsidence of the ground surface caused by coal mining is a serious environmental problem in many countries. Therefore, an effective monitoring and prediction system must be established in coal mining areas to protect nearby property and the surrounding environment. In this paper, a model is proposed that integrates differential interferometry synthetic aperture radar (D-InSAR) technology and the support vector regression (SVR) algorithm to monitor and dynamically predict mining subsidence. D-InSAR technology is first used to monitor the range of influence and the development trend of mining subsidence, thus obtaining the law of surface subsidence. Based on the monitoring results obtained by D-InSAR technology, the SVR algorithm is used to describe the nonlinear function correlativity between the monitored data and future subsidence. As the performance of the SVR algorithm depends largely on the choice of relevant parameters, the particle swarm optimisation (PSO) algorithm is introduced to select ...

Galileo IOV RTK positioning: standalone and combined with GPS

Abstract: Results are presented of real time kinematic (RTK) positioning based on carrier phase and code (pseudorange) observations of the four Galileo In-Orbit Validation (IOV) satellites, as they were in orbit and transmitting navigation data at the time of writing this article (2013). These Galileo data were collected by multi-GNSS receivers operated by Curtin University and as such this article is one of the first presenting results of short baseline ambiguity resolution and positioning based on Galileo IOV observations. The results demonstrate that integer ambiguity resolution based on the four IOV satellites needs fewer than three minutes when at least observables from three frequencies are used. Combined with data of four GPS satellites even instantaneous (single epoch) ambiguity resolution is demonstrated, using only two frequencies per constellation (i.e. E1+E5a & L1+L2). We also show that at locations with obstructed satellite visibility, such that positioning based on either GPS-only or Galileo-o...

Postseismic deformation after 2008 Wenchuan Earthquake

Abstract: Apparent postseismic deformation was observed after the 2008 Wenchuan earthquake, China. The displacement in the direction normal to the fault decays to nearly zero after 2013, but the significant dextral movement did not decay obviously during our observation of up to May 2013. It indicates that the stress paralleled to the fault in the southern part of the rupture zone was not relaxed during the coseismic slip. The unrelaxed stress transfers northward after the earthquake and continues after 2013. The postseismic deformation may be dominated by afterslip or stress readjustment, but the effects of the viscoelastic relaxation also cannot be ignored. The low velocity zone under the Bayan Har block, which is velocity strengthening, may greatly affect the postseismic deformation and makes it possible that the lower crust ductile flow and the shortening of the crust both contribute to the uplift of the Longmen Shan. The viscoelastic coefficients of the low velocity zone and the lower crust should be l...

TLS algorithm for GPS height fitting based on robust estimation

Abstract: Application mathematical model for GPS height fitting problem, rational fitting model and accurate parameters of fitting model have impact on the final fitting accuracy. It is known that researchers are used to applying least squares (LS) to establish Gauss–Markov model (G–M model) for computation parameters of mathematical models to realise GPS height fitting. The premise of establishing G–M model based on LS is under the assumptions that coefficient matrix of fitting model is error-free, and random error exists only in observation data. However, two kinds of factors mean that this hypothesis does not exist exactly: first, both coefficient matrix and observation data of control points have random error unavoidably; second, gross error may exist in observation data. In this paper, a solution is presented to solve the problems due to these factors. To take into account random error both in coefficient matrix and observation data while computing the parameters, method of establishing G–M model based on tota...

Different approaches of visibility analyses applied on hilly urban environment

Abstract: The work reported in this paper is a contribution to the search for reliable visibility evaluation method for the urban environment. We examine three analysis models: 1. Point based visibility graph of street network based on , 2. Voxel based volumetric visibility analysis (Fisher-Gewirtzman et. al., 2013) and 3. Line Of Sight (LOS) based visibility analysis (Fisher-Gewirtzman and Elber, 2013). We compare between these models to explore their suitability to a hilly urban spatial configurations. We describe the similarities and differences. In this study we carry out a test comparing the value of visibility degree centrality for street network to the assessments of 3D Voxel and LOS visibility analyses. Our results demonstrate that junctions with similar rankings in all three models were located in a fairly flat topography and all the junctions with different rank were located on the border of a sloping topography. Their visibility was influenced by the changing topography. This preliminary study wi...

Gauss–Jacobi combinatorial adjustment and its modification

Abstract: Many determined nonlinear systems in geodesy are analytical. C. F. Gauss and C. G. J. Jacobi ever developed an adjustment technique, later called as Gauss–Jacobi combinatorial method, to obtain an optimal solution of an over-determined nonlinear system. Nowadays, facing new development in abstract algebra, the potential of these contributions becomes clearer that this method can analytically solve an over-determined nonlinear system only if the determined sub systems are analytical. An important subject, that determines whether this method is rigorous, is to discuss the relation between the combinatorial estimator and the nonlinear least squares estimator. In this paper, we first introduce the Gauss–Jacobi combinatorial method in the context of the Gauss–Newton iterative equation, and illustrate what manifests the accuracy of the Gauss–Jacobi combinatorial estimator. It shows that high nonlinearity, large residuals or ill conditioning can cause the Gauss–Jacobi combinatorial estimator to be inaccu...

On ‘decorrelation’ in solving integer least-squares problems for ambiguity determination

Abstract: This paper intends to shed light on the decorrelation or reduction process in solving integer least squares (ILS) problems for ambiguity determination. We show what this process should try to achieve to make the widely used discrete search process fast and explain why neither decreasing correlation coefficients of real least squares (RLS) estimates of the ambiguities nor decreasing the condition number of the covariance matrix of the RLS estimate of the ambiguity vector should be an objective of the reduction process. The new understanding leads to a new reduction algorithm, which avoids some unnecessary size reductions in the Lenstra-Lenstra-Lovasz (LLL) reduction and still has good numerical stability. Numerical experiments show that the new reduction algorithm is faster than LAMBDA’s reduction algorithm and MLAMBDA’s reduction algorithm (to less extent) and is usually more numerically stable than MLAMBDA’s reduction algorithm and LAMBDA’s reduction algorithm (to less extent).

Effect of subnetwork configuration design on deformation analysis

Abstract: Deformation analysis plays an important role for human safety so that investigating the reliability of the obtained results from deformation analysis is extraordinary important. It uses statistics most widely and if H0 hypothesis is rejected in applying of the global congruency test, the localisation process is performed to detect one or more displaced points. There are a lot of methods for localisation and they do not have the same and correct results for all cases. Their reliabilities change according to samples, the numbers of displaced and stable points in the network, and the magnitudes of the displacements. There are two reasons for the unsuccessful results of the conventional deformation analysis (CDA) methods: the first is the spreading effect of Least Squares Estimation (LSE); the second is the failure of F-test. LSE is an optimal estimator when observations come from normal distribution, i.e. there is not any outlier in the data set. However, if the observations are non Gaussian, i.e. if...

Spatio-temporal modelling of dam deformation using independent component analysis

Abstract: Modelling dam deformation based on monitoring data plays an important role in the assessment of a dam’s safety. Traditional dam deformation modelling methods generally utilise single monitoring point. It means it is necessary to model for each monitoring point and the spatial correlation between points will not be considered using traditional modelling methods. Spatio-temporal modelling methods provide a way to model the dam deformation with only one functional expression and analyse the stability of dam in its entirety. Independent component analysis (ICA) is a statistical method of blind source separation (BSS) and can separate original signals from mixed observables. In this paper, ICA is introduced as a spatio-temporal modelling method for dam deformation. In this method, the deformation data series of all points were processed using ICA as input signals, and a few output independent signals were used to model. The real data experiment with displacement measurements by wire alignment of Wuqiangxi Dam was conducted and the results show that the output independent signals are correlated with physical responses of causative factors such as temperature and water level respectively. This discovery is beneficial in analysing the dam deformation. In addition, ICA is also an effective dimension reduced method for spatio-temporal modelling in dam deformation analysis applications.

Verification technology for topological errors in official databases with case study in Poland

Abstract: Topological correctness of objects is an issue demanding solution in all undertakings related to the creation spatial databases. This article presents the technology for detection and elimination of topological errors in official databases (real estate cadastres, Land Parcel Identification System (LPIS)). The method for working on virtual objects in computer aided design (CAD) environment has been developed. This method can be successfully used for spatial databases, where large numbers of objects are elaborated. The suggested algorithm for verifying the topological correctness of surface objects was implemented in the years 2010–11, with the update of LPIS system databases, carried out by the Ministry of Agriculture in Poland. This technology received positive assessment in the course of the works undertaken.

Development of NSDIs in Western Balkan Countries in accordance with INSPIRE

Abstract: The INSPIRE Directive requires actions from EU member states and also has direct implications on the countries in the neighbourhood of the EU, regardless of whether they are candidate countries or not. Preconditions for EU membership, to which actually all the countries of Western Balkan (WB) countries aspire is their administrative capacity to incorporate the EU acquis, to fulfil the adopted standards and to execute the assumed obligations. INSPIRE Directive is just one but very important piece of legislation in environmental acquis and is a part of negotiation processes between the European Commission and candidate countries. This paper provides an analysis of the existing status and conditions of National Spatial Data Infrastructures (NSDIs) in WB countries. Results of analysis clearly show that in all countries there are ongoing initiatives on NSDI implementation in line with INSPIRE. The level of implementation between countries however differs but they are all on the right track. In the paper the ma...

Assessment of PPP for establishment of CORS network for municipal surveying in Middle East

Abstract: Nowadays many Continuously Operating Reference Stations (CORS) network were established in the Middle East to improve different municipal surveying. Establishing such geodetic control networks can be a costly business where multiple stations should be occupied simultaneously and post-processed with scientific software. Recently, precise point positioning (PPP) has attracted wide interest because it provides an alternative to precise relative processing due to its potential as a reliable absolute positioning technique operational simplicity. In comparison with common relative GPS techniques, the costs are reduced; because no base stations and no simultaneous observations are necessary. This research investigates the capability of PPP approach to be a low cost alternative to the conventional positioning methods used in coordinates determination of geodetic networks. The GPS data used during setting up Jeddah municipality network were originally processed by Bernese software version 5.0. That GPS dat...

Effect of Thai Ionospheric Maps (THIM) model on the performance of network based RTK GPS in Thailand

Abstract: In 2008, the DOL-NRTK (Department of Lands-Network-based Real Time Kinematic) GPS system was established to support cadastral surveying applications in Thailand using the Virtual Reference Station (VRS) concept. Currently the DOL-NRTK network consists of 11 reference stations located in the Central Plain region of Thailand with spatial coverage ranging from 30 to 125 km with an average spacing around 60 km. A previous study confirmed that ionospheric errors are the main error sources that affect the NRTK performance. Also the ambiguity fixing success rate was significantly improved when the final Global Ionospheric Maps (GIM) from the Center for Orbit Determination in Europe (CODE) were applied. However, the final GIM is the global model and may not perfectly fit with smaller regional test areas in Thailand. Therefore, an investigation on the use of a regional ionospheric model was required. In this paper, the Thai Ionospheric Map (THIM) generated by the Bernese software is described. An investiga...

Monitoring deformation of small scale model tunnels under load testing

Abstract: This paper describes a study to assess the suitability of two non-contact methods of measurement used to monitor a series of small scale model tunnels built to different specifications that are being subjected to load testing. The model tunnels are being built to validate mathematical modelling techniques. Presented here are the results to assess the suitability and quality of survey results based on photogrammetry and laser scanning. The two key parameters to be measured are the deformation that is created in the tunnel (distance measurement) and the length and width of cracks. Results showed that both the remote measurement techniques were suitable for the measurement of the small model tunnels and compared well against appropriate potentiometer and vernier calliper measurements.

Research on methods of regional ionospheric delay correction based on neural network technology

Abstract: A new model for regional ionospheric delay correction has been developed, tested and compared with a two-dimensional polynomial ionosphere delay correction model (called 2-DPM). First, available ionospheric data have been used in the modelling of the 2-DPM. Then, artificial neural network technology is used to compensate for the model deviation Δy of the 2-DPM to obtain a new ionospheric delay correction model (called the Fusion model). Finally, an example is implemented to demonstrate the performance and efficiency of the Fusion model. According to the statistical analysis of average root mean squared errors, the Fusion model offers an improvement of 26·4% over the 2-DPM. The results show that the proposed model can give better accuracy than the 2-DPM.

Proposed guidebook on established case law for land surveyors on property boundaries

Abstract: Since the introduction of the common law system, precedent case law has been a core element of its existence. Owing to the high number of boundary surveys conducted as part of boundary disputes during the past number of years, research of Irish High Court case law judgements delivered in the past 10 years on property boundary disputes was identified. This paper outlines a proposal to be considered in the form of a ‘Guidebook’ for surveyors to follow when involved in a property boundary dispute. The court judgements will be assessed via a case briefing technique that is used worldwide in universities and an understanding of surveying case law and how decisions can be used in the construction of principles to be applied will be evaluated and analysed. Detailed information on these cases is not the subject of this paper. This paper presents results documenting how case law can be seen to be of fundamental importance for surveyors when involved in property boundary disputes. Documented in the form of ...

Precise determination of mini railway track with ground based laser scanning

Abstract: In order to determine the relative or absolute railway track and foundation deformation, ground-based laser scanning technology is utilised in this study to attain a precise 3D track reference. Located at the University of Nottingham’s Innovation Park, the newly built Nottingham Geospatial Building, where the Nottingham Geospatial Institute is based, has a roof laboratory that has unique testing facilities. This includes a mini railway track of 120m in length and other long-term monitoring monuments. A test was performed to precisely determine the ground-truth location of the railway track using a phase-based laser scanner for the formation of a standard reference. A real three dimensional mesh of the laser scanning data forms the basis for the line extraction. The compactly supported radial basis function (CS-RBF) was employed to determine the track features based on a 3D mesh approach. To verify the achievable accuracy of laser scanning technology, ground truth points measured with geodetic methods are compared with the extracted sample points and the results are presented in this paper.

Development and application of deformation monitoring system for lanslide at Funchunjiang Dam

Abstract: Under the background of the landslide deformation monitoring of the left mountainside at Fuchunjiang Dam, we developed an automatic Landslide Deformation Monitoring System (LDMS) based on the TCA2003 surveying robot. Our LDMS extended the applications of TCA2003 in deformation monitoring by using GEOCOM serial-port functions. The system has the following features: automatic multiple observation sets measuring, automatic field data sheets generating, hydrograph plotting and deformation analysing. The new system had been developed and implemented under the environment of Visual C++ 6·0. The system has simpler operations and stronger practical applicability, compared with previous landslide deformation monitor methods. Based on analysis of the coordinates of Leftpt point on the sliding mass of left mountainside on Fuchunjiang Dam, displacement occurred in recent years, the whole monitoring of the sliding mass is essential. The analysis of the data achieved by LDMS showed that the sliding mass had no ...

Geometry-free and non-geometry-free testing quantities for cycle slip detection and correction in case of strong atmospheric variations with static observations

Abstract: Cycle slip detection and correction is an important part of GPS data processing. In the past research, geometry-free and non-geometry-free testing quantities have been proposed. Both of them can be used for static cases. Each of them has their own advantages and disadvantages. This research is aiming to compare these two kinds of testing quantities for static cycle slip detection and correction in different situations, such as in low and high elevation angles, especially in cases of strong atmospheric variations. The performance of geometry-free and non-geometry-free testing quantities is compared with observations of different situations. The numerical results show that the effect of the rapid change of relative humidity on cycle slip detection and correction with these two kinds of testing quantity is not obvious. However, the results clearly show that in the case of a low elevation angle (<10°), non-geometry-free is obviously a better choice. In the case of ionospheric scintillation, geometry-f...