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Survey Review 46, No 339. November/December 2014

Special issue on the Second Joint International Symposium on Deformation Monitoring (JISDM), University of Nottingham – 9-11 September 2013. Guest edited by Xiaolin Meng, Yang Gao and Wujiao Dai

1. Guest Editorial
Dr Xiaolin Meng; Mr Yang Gao; Dr Wujiao Dai

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2. Integration of D-InSAR technology and PSO-SVR algorithm for time series monitoring and dynamic prediction of coal mining subsidence
B. Q. Chen; K. Z. Deng

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 the optimal parameters for the SVR algorithm. Finally, a method of rolling prediction based on the optimised SVR parameters is adopted to update the training and learning samples of SVR, thus allowing the algorithm to use the latest monitored data to dynamically predict future mining subsidence. To verify the applicability of the proposed methodology, it was applied to a coal mining area in Neimeng, China, where thirteen TerraSAR-X images were acquired from 21 November 2012 to 2 April 2013. The experimental results show that the monitoring results very accurately reflect the range of influence and the trend in the development of mining subsidence and also that the PSO-SVR algorithm provides high-accuracy prediction results with a maximum absolute error (MAE) of 29 mm and a maximum relative error (MRE) of 6·5%, thus demonstrating the accuracy and feasibility of the proposed model.

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3. Comparison of two unconventional methods of estimation applied to determine network point displacement
R. Duchnowski; Z. Wiśniewski

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.

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4. Surveying adjustment datum and relative deformation accuracy analysis
G. L. Chen; X. Meng; L. B. Yao

In the surveying adjustment, unknown parameters are usually not direct observations, but the elements related to these direct observations. In order to determine the unknown parameters adequate known data should be provided, and these necessarily required known data are used to form the adjustment datum. Under different datums, different results will be obtained even with the same direct observations. However, in the practical adjustment calculation, the datum and its effect on the results are always ignored. In this paper, the adjustment datum is firstly discussed and defined as datum equations. Then an adjustment method based on the datum equations and least squares is presented. This method is a generic one, not only suited for the case in an ordinary datum but also in the gravity centre datum or a quasi-datum, and can be easily used to analyse different deformations. Based on this method, the transformation between different reference frames is derived. It shows that the calculation results, deformation and positioning accuracy under one kind of datum are relative and generic. A case study is further introduced and used to test this new method. Based on the case study, the conclusions are reached. It is found that the relative positional root mean square error of each point becomes bigger as the distance between the point and the datum increases, and the relative deformation offsets under different kinds of datum are helpful for reliable deformation analysis.

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5. Analysis of ill posedness in double differential ambiguity resolution of BDS
S. G. Pan; W. Gao; S. L. Wang; X. Meng; Q. Wang

The ill posedness in a variance–covariance matrix will directly determine the convergence speed and accuracy of integer ambiguities. Unlike GPS or GLONASS, BDS (BeiDou Navigation Satellite System) consists of not only MEO satellites but also GEO and IGSO satellites, both of which are high orbit satellites. The angular velocities of the GEO and IGSO satellites are much smaller compared with MEO satellites. The changes of the geometric structure between satellites and stations of the high orbit satellites GEO/IGSO in BDS are not obvious during short observational spans due to their relatively small angular velocity. This results in stronger correlation of equations between adjacent epochs while calculating ambiguities, leading to serious ill posedness. In this paper the ill posedness of double differential (DD) ambiguity resolution (AR) of the current BDS was analysed. On this basis, some different combinations of GEO, IGSO and MEO satellites of BDS were used in the AR experiments to reveal the characteristics of ill posedness. Moreover, AR experiments of GPS, GLONASS and BDS/GPS/GLONASS fusion were also carried out for comparison with BDS. These experiments indicate that the AR of the current BDS is a more serious ill posed problem, and therefore takes much more time for AR fixing than GPS or GLONASS. The fusion with GPS or GLONASS, however, will solve the ill posed problem effectively and improve the AR much more, achieving fixes even instantaneously.

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6. Monitoring deformation of small scale model tunnels under load testing
H-M. Chen; M. Smith; H-S. Yu; N. Kokkas

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.

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7. FARSE scheme for single epoch GPS solution based on DUFCOM and DC algorithm and its performance analysis
J. M. Guo; M. D. Zhou; J. B. Shi; C. J. Huang

Fast integer ambiguity resolution for single epoch observation is one of main issues of GPS precise positioning in real time surveying applications. An improved solution of dual frequency correlation method (DUFCOM) and direct calculation method (DC), named as fast ambiguity resolution for single epoch scheme (FARSE), is proposed in this paper. A software based on the proposed scheme for monitoring of construction cranes, Gsertcas, is developed. With the help of Gsertcas, the performance and suitability of FARSE are investigated through simulation experiments. The result of the experiment demonstrates that the success rate for ambiguity resolution is above 97% and the root mean square of the position solution with correct ambiguity resolution is better than 3·8 mm.

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8. Postseismic deformation after 2008 Wenchuan Earthquake
C. J. Xu; Q. B. Fan; Q. Wang; S. M. Yang; G. Y. Jiang

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 larger than 3×1018 Pa.s which is optimised with our observations by using the single viscoelastic relaxation model.

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9. Spatio-temporal modelling of dam deformation using independent component analysis
W. Dai; B. Liu; X. Meng; D. Huang

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.

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10. Development and application of deformation monitoring system for lanslide at Funchunjiang Dam
L. B. Yao; H. L. Sun; L. X. Zhu; Y. Y. Zhou

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 clear uniform deformation, and each part of the sliding mass was noticeably different in the slipping speed in the landslide direction. Hence, regular monitoring is essential to prevent the sliding mass from local landslides.

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11. Book Review
Arthur L. Allan

Geodesy: Theory and Practice. Peter Biro, Joszef Adam, Lajos Volgyesi, Gyula Toth. Budapest University of Technology and Economics, Dept of Geodesy and Surveying, 1521 Budapest, Hungary. 508 pages. Price 12 Euros. ISBN 978-963-257-248-2.

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Survey Review 46, No 338. September/October 2014

Special issue on FIG Commission 3 annual conference (International Conference on “Spatial Data Infrastructures & Spatial Information Management 2013”) Skopje, Former Yugoslav Republic of Macedonia - 13-16 November 2013

1. Usage of European census data for sustainable land management – German case study
U. Klein; H. Müller

This paper describes opportunities and results of the usage of high resolution census data for sustainable land management. Following European Union requirements many countries in Europe have counted their population and other indicators in 2011. To take full benefit of the very rich high resolution census data in Germany some country specific problems had to be solved. By applying a semi-automatic procedure the study describes in which way the official topographical and property information systems provided by the surveying authorities are used to determine the boundaries of small scale census units. Linking the census data to the corresponding geographical units enables public administration bodies and other stakeholders to realise the full potential of high resolution census data. Once a data set has the described structure a broad range of thematic maps can be created from it, and the complete scale of spatial analysis functions can be applied to such data. Four typical scenarios are demonstrated to prove the benefit of the developed solution in the planning practice of German municipalities.

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2. Development of NSDIs in Western Balkan Countries in accordance with INSPIRE
V. Cetl; K. Tóth; P. Smits

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 main existing and future achievements are discussed together with a SWOT analysis. Paper also complements the INSPIRE State of Play Report from 2011, especially with the situation in the countries for which there is no such consistent information available. Finally, some conclusions and recommendations for further developments are given to foster and help WB countries in their efforts to develop NSDIs in accordance with INSPIRE.

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3. 3D cadastres: legal approaches and necessary reforms
D. Kitsakis; E. Dimopoulou

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 in rem, or through the introduction of 3D property units. The latter approach which was firstly introduced in Common Law jurisdictions is gradually adopted by Civil Law jurisdictions. Both jurisdictions share similar concepts although they are differentiated in structural, terminological, cadastral infrastructure and implementation aspects.

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4. Research on residential property taxation and its impact on the real estate market in Greece
M. Filippakopoulou; C. Potsiou

The purpose of this research is to identify the differences between the ‘objective’ (tax) values and the current true market values of residential real estate in Greece. For that purpose research is made on the tax values used by tax authorities and the manner of their definition. In the first part of this paper an updated review of all taxes currently levied on residential property in Greece on the transfer (as a property transfer tax) and on the possession of residential properties (as Periodic Annual Taxes) is given. Then the calculation of the ‘tax values’, by the objective mass valuation system of the Greek tax authorities is presented and its variations are explained. In order to investigate the true market values and compare those with the tax values a case study is carried out. The Greater Athens Municipality is chosen because of its size, market importance and diversity. A specific methodology is followed to establish solid criteria for the sample selection, and then the results are compared to the tax values taken through the State’s mass valuation system. Furthermore, an overview of the Greek real estate market (2007 – to date) is made, so as to provide the context within which the current research is based. The results of this research reveal a discrepancy between the tax assessed values and the true market values in residential property in Greece, the latter ones being either equal or lower depending mainly on the age of the property. Although at the beginning of 2013 new buildings still might retain a market price slightly above the tax assessed value, older buildings followed an opposite trend, which was relative to their age. This showed a major flaw in the calculation methods of the tax assessed values (objective mass valuation system) that should be rectified at the earliest opportunity. By the end of 2013 the already critical situation of the Greek real estate market deteriorated even further. The decline in asking prices accelerated and the transaction volume decreased due to a lack of demand, liquidity and limited bank lending. The result of this is that the transaction prices of the few recorded transactions that took place in 2013 were realised at a level 15% lower compared with the 2012 transactions. Very few newly built properties were sold at a price equal or marginally higher than the taxable value though the vast majority of the properties were sold at prices as low as 50% of the taxable value. Greek government shows no intention to adjust taxable values before 2016. This policy discourages potential buyers and causes irrevocable harm to the real estate market.

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5. Assessment of the global digital elevation models ASTER and SRTM in Greece
C. Ioannidis; E. Xinogalas; S. Soile

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 56°S to 60°N and ASTER GDEM with coverage from 83°S to 83°N, 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.

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6. Triangulation based topology approach for 2D point sets registration
G. Ben-Haim; S. Dalyot; Y. Doytsher

Registration is designed to overcome global spatial correspondence ambiguities of different spatial databases and is required as a first stage in integration. It aims at ensuring an accurate and qualitative match while avoiding erroneous or coinciding data-features in the final product. The algorithm presented in this research paper describes an automatic constraint-free robust homological feature based registration of two 2D point sets. The points represent features of interest that exist in spatial databases, e.g. maps and topographic datasets. The algorithm entails an iterative aggregative voting process that consists of a set of qualitative statistical quantifications, based on the correspondences of triangulation structure, aimed at evaluating the geometric similarity of the data. The algorithm is structured to overcome data ambiguities, including data outliers and noise. The automatic aggregative voting algorithm replaces the need for a-priori spatial knowledge or the use of manual or semi-automatic registration that is prone to error. A comparison of the proposed automatic registration with alternative commonly used processes is presented, showing better and robust results. As such, the presented algorithm proves as an important stage towards the qualitative integration and enhancement of spatial databases.

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7. Different approaches of visibility analyses applied on hilly urban environment
D. Fisher-Gewirtzman; A. Natapov

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 Jiang and Claramunt, (2002), 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 will be followed by more comprehensive research looking at a variety of urban, architectural and topographic conditions. These findings may provide planners and designers with information about factors that affect the visibility of the urban environment and may put forward new ideas to improve the existing measurement tools.

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8. Defining methodology for selecting most appropriate GIS software
B. Idrizi; S. Zhaku; S. Izeiroski; I. Kabashi; P. Nikolli

Selecting the most appropriate software package for project purposes and developing GIS systems up to establishing spatial data infrastructure, is one of main efforts in project preparation and commencement phases. Correct selection means the right way for developing a dataset and data infrastructure, lower costs for software purchasing and maintenance, reducing budgets for data development and updating systems, harmonisation of data at national and regional level, the use of latest information technology, adopting applications with the available system and hardware requirements of the technology of the organisation, and getting better support from software providers and developers, etc. The objective of this paper is to introduce the methodology utilised for selecting the most appropriate GIS software for developing a GIS application about one year ago. All data in the eight tables represent are real data, which compare eight different software packages. Names of software are not given in this paper, to avoid any conflict of interest and indirect positive/negative marketing of software which were used in our research. The methodology for the analyses contains eight tables, with eight different topics which are directly related to cost benefit analyses, types of software support by providers and developers, difficulties in developing, using and upgrading GIS applications, system and hardware requirements, and development languages. From the analyses performed, data in three tables (system requirements, hardware specification and development languages) did not show significant differences between different GIS software, so they were excluded from further analysis to select the most appropriate GIS software. Therefore another five criteria have been used as reference data with these variables and weights: server license price with five year regular upgrade 40%, desktop price with five year regular upgrade 15%, application development price 25%, support 10% and running/development difficulties 10%. Owing to large differences in price, the main challenge in the analyses was selecting between commercial software and free and open source software (FOSS). Apart from very big differences in price for the software licenses (from 249 250€ to 0€), one commercial software package scored 64 points, while both FOSS scored 66 points. This result shows very clearly that while FOSS is software is free, the difficulties for application development and infrastructure support are greater than for commercial software. The methodology defined in this paper should be taken into consideration as a basic platform for selecting the most appropriate GIS software for project purposes. Based on specific requirements of GIS projects, this line of analyses should be extended, in order to fulfil the project specifications and expectations.

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Survey Review 46, No 337. July/August 2014

1. Rectification of position data of Scotland in Ptolemy’s Geographike Hyphegesis
C. Marx

The ancient geographic coordinates given for places of Great Britain in Ptolemy’s Geographike Hyphegesis are investigated by means of geodetic methods. The turning of Scotland to the east is modelled by a three-dimensional rotation. On the basis of different data sets of control points, the parameters of the rotation are estimated by means of methods of adjustment theory. Furthermore, a geodetic-statistical analysis method is applied to Scotland, by which groups of places of homogenous distortions and modern counterparts of the ancient places are determined. Based on the results of the investigations, answers are given for questions concerning Ptolemaic positions unsolved so far.

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2. First astronomical reference meridian in Norway
B. R. Pettersen

The first geodetic reference frame in Norway was established by triangulation 1779–1799. In 1785 the formal decision was made to establish the reference meridian in Trondheim. Latitude determinations had already been made in 1782–83 by observing meridian transits of the sun and stars with a geographical circle. Additional instruments were added to equip a small observatory. Time determinations were made with a transit instrument and pendulum clock. Lunar occultations and eclipses of the sun, moon, and Jovian satellites were observed with a Dollond refractor for longitude determination. This activity continued till 1791 when the instruments were transferred to Bergen to establish a control meridian there. We have searched archives in Denmark and Norway to recover original observations, correspondence, and other documents. This allows us to trace the history and to reanalyse observational data to determine statistical uncertainties and gain insight into systematic effects. Observing sites have been identified and allow comparison between historical results and modern GPS measurements.

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3. Method of recovering municipal boundary lines in Province of Valencia (Spain) by means of historical cadastral maps
C. Femenia-Ribera; E. Benitez-Aguado; G. Mora-Navarro; J. Martinez-Llario

Land demarcation is a fundamental requirement when determining to what extent property owners and public administrations can apply their rights. Just as international boundaries must be clearly marked so that there can be no doubt as to which jurisdiction is to be applied, municipal boundaries must be clearly defined in order to avoid disputes between local administrations. In Spain the Geographical Institute carried out the demarcation of all municipal boundaries at the end of the 19th and beginning of the 20th centuries, defined their limits on cadastral maps and represented them on the 1∶50 000 scale National Topographical Map. At the present time, more than a hundred years after this survey, in many cases parts of the original municipal limits have been lost for one reason or another, both on the maps and on the ground itself, and it has now become necessary to take steps to recover them. This paper defines a method of using the municipal councils’ own historical information to trace original boundary lines. The work included both a study and a series of tests carried out in different municipal areas in the Province of Valencia, Spain. The original reports and field notebooks of the Geographical Institute were used as the basic material of the study, supported by cadastral maps from different periods, as well as historical and contemporary orthophotos to help locate possible boundary markers. GPS techniques were employed to look for, survey and reinstate boundary marker positions.

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4. Galileo IOV RTK positioning: standalone and combined with GPS
D. Odijk; P. J. G. Teunissen; A. Khodabandeh

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-only becomes impossible or only in a very inaccurate way, combined Galileo&GPS positioning is feasible, within 10 min if one frequency of each constellation is used and only 2 min time-to-fix the ambiguities based on observations of two frequencies of each constellation. It is furthermore demonstrated that this results in positions with centimetre level accuracy in the horizontal plane and sub-decimetre accuracy in the vertical direction.

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5. Accuracy of single receiver static GNSS measurements under conditions of limited satellite availability
K. Dawidowicz; G. Krzan

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 conducted under conditions of limited satellite availability and processed using various types of GNSS services. The PPP-CSRS service was chosen as an example of a PPP service. For differential processing mode, the ASG-EUPOS service was selected. The analysis was based on four days of data from three GNSS stations. The PPP-CSRS results show that horizontal accuracies of ∼5 cm and vertical accuracies of 10 cm are achievable provided 0·5 h of open sky and low multipath dual frequency GNSS data. Accuracy clearly decreases for points measured under conditions of limited satellite availability. Analogous ASG-EUPOS service accuracies are noticeably better.

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6. Triple carrier precise point positioning (PPP) using GPS L5
J. Tegedor; O. Øvstedal

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.

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7. Gauss–Jacobi combinatorial adjustment and its modification
S. Q. Xue; Y. X. Yang

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 inaccurate. Then, employing the high order Taylor approximation we propose a modified combinatorial method to improve the Gauss–Jacobi combinatorial estimator. Finally, in order to show when and why one should employ the high order combinatorial technique proposed, the first order combinatorial method and the second order combinatorial method are both applied to solve over-determined distance equations. It shows that the second order combinatorial estimator is more accurate than the first order combinatorial estimator.

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Survey Review 46, No 336. May/June 2014

1. Performance evaluation of short to long term GPS, GLONASS and GPS/GLONASS post-processed PPP
C. O. Yigit ; V. Gikas ; S. Alcay ; A. Ceylan

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 PPP solutions for the very long (several weeks) observation periods irrespectively of the satellite constellation used.

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2. Research on methods of regional ionospheric delay correction based on neural network technology
W. S. Hu ; D. Y. Zheng ; W. F. Nie

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.

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3. Rapid GNSS ambiguity resolution using dual frequency integer relationship constrained algorithm
W. Feng ; D. F. Huang ; L. T. Zhou ; X. Zhang ; L. Yan

The accuracy of pseudorange is critical to fast ambiguity resolution (AR), especially for single epoch AR. To achieve rapid and reliable positioning with the dual frequency global navigation satellite system (GNSS) receivers for short baseline applications, we propose an integrated method called dual frequency integer relationship constrained ambiguity resolution (FirCAR). FirCAR reduces the required accuracy of pseudorange measurements in the AR procedure of each high elevation satellite. The ambiguities fixed by FirCAR are then added into the observation equation to improve the accuracy of the float ambiguity solution for the remaining measurements at relatively low elevation. Depending on the improved accuracy of the float ambiguities, fixing ambiguities becomes easier through a round-off and/or a search algorithm. On-the-fly (OTF) AR experiments were conducted for static and kinematic GPS observables over short baselines (<13 km). These experiments prove that FirCAR can effectively reduce the observation epochs required to resolve ambiguities, compared to commonly used methods, especially in conditions that are challenging for GPS (e.g. few satellites available, high multipath). More than 95% of the ambiguities can be solved with a single epoch observation using the proposed AR procedure.

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4. TLS algorithm for GPS height fitting based on robust estimation
Y.-Q. Tao ; J.-X. Gao ; Y.-F. Yao

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 total least squares (TLS) is discussed, and to take into account that the accuracy of observation data is unequal because of gross error, method of applying TLS algorithm to compute parameters based on robust estimation is proposed. We cite instances to prove that the solution is feasible, in the instance, weight of control point which contains gross error is computed by iteration. And the numerical results from our experiment clearly demonstrate that compared with LS and TLS, mean square error of parameters which is computed by the robust TLS is more accurate, and conclusions can be drawn that application robust TLS for GPS height fitting is more scientific.

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5. Algorithm for purposes of determining real estate markets efficiency with help of land administration system
A. Dawidowicz ; A. Radzewicz ; M. Renigier-Biłozor

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.

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6. Jurisdictional boundaries in Spain, survey and marking of boundaries in Teruel (Spain)
N. Garrido-Villén ; J. L. Berné-Valero ; A. Antón-Merino ; A. Anquela Julián

In the 1890s and early 1900s, the National Geographic Institute (IGN) of Spain carried out geodetic studies required to georeference the boundaries of every single municipality in Spain, survey the boundaries and mark them out. The field notes for these studies still exist and can still be referenced today. Nowadays, most of the landmarks that were located in these studies have disappeared; replacing these monuments could be of great interest to the local government, both administratively and economically. The indeterminacy or change of municipal boundaries can lead to tax collection and even supply problems. This paper studies the accuracy of those studies. Furthermore, a technical method for locating the lost monuments is shown; this method could also be used to map the monuments in a precise and reliable way. In this way, the problem of replacing boundaries is subsequently analysed.

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7. Precise determination of mini railway track with ground based laser scanning
X. Meng; C. Liu ; N. Li ; J. Ryding

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 120 m 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.

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8. Registration of vector maps based on multiple geometric features in topological aspects
J.-Y. Han ; J. Guo ; Y.-J. Chen

Maps are one of the most intuitive tools for recording and representing geographic information. Digital maps composed of vectors are mostly used for preserving cartographic data in a compact and efficient manner. However, the registration of multiple vector maps is an essential step when geographic information from various sources is used in an integrated analysis. Typically, control points are used as observables to solve the transformation parameters of a registration model, while check points are used for quality assessment. As a consequence, poor distribution or an insufficient number of control or check points might lead to a biased registration solution. In this study, linear features and projective invariant points were both used as observables in a registration analysis between multiple vector maps. The goal was to provide an improved geometric constraint when solving the transformation parameters. Furthermore, two numerical indices, namely the absolute consistency and relative geometric similarity, were used to evaluate the quality of the registration solution. Based on the results of a case study, the proposed approach has been shown to be capable of better making use of the geometric connotation inherent in a vector map and providing a comprehensive quality evaluation for the obtained transformation solution. Consequently, a more reliable and robust registration analysis for digital vector maps can be achieved when the proposed approach is implemented.

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Survey Review 46, No 335. March/April 2014

1. 3D+time Cadastre, possibility of implementation in Poland
M. Siejka ; M. Ślusarski ; M. Zygmunt

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.

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2. Land privatization in urban Mongolia: an observation
B. Nyamdorj ; P. van der Molen ; A. M. Tuladhar

The land privatization process in Mongolia mainly concerns residential land. The process is considered to perform slowly. The deadline for free allocation of residential land was extended from 2005 to 2013. Still, the number of families that have acquired private landownership during that period is low. This paper aims to take a closer look at the operational process in Ulaanbaatar. The paper finds that, when citizens apply, in a majority of cases the legal deadline to be granted a land-ownership right is actually met. An observation is that this apparent ‘successful’ process management is made possible by a limitation of input of applications. In conclusion, the current land privatization process in Mongolia features a lack of information about privatization areas, lack of citizen involvement in the choice of areas to be privatized and a de facto influx regulation leading to frustration. The paper concludes with policy advice for improvement.

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3. Assessment of PPP for establishment of CORS network for municipal surveying in Middle East
A. I. EL-Hattab

Nowadays many Continuously Operating Reference Stations (CORS) network are 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 data were processed again using PPP approach and comparable investigation was carried out between the coordinates obtained from Bernese software and CSRS-PPP software. The results showed that overall CSRS-PPP solutions agreed with the Bernese solutions, where the Root Mean Square of the difference between the two solutions reaches 2·6 mm in Easting, 2·5 mm in Northing, and 10 mm in Height. The derived centimetre accuracy from PPP approach which is suitable for municipal surveying confirmed that it can be used for establishment of CORS networks.

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4. Geometry-free and non-geometry-free testing quantities for cycle slip detection and correction in case of strong atmospheric variations with static observations
S. Y. Ji ; Z. J. Wang ; W. Chen ; D. J. Weng ; Y. Xu ; S. J. Fan ; B. H. Huang ; G. Y. Sun ; H. Q. Wang ; Y. W. He

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-free testing quantity can no longer be used. With non-geometry-free testing quantity, cycle slips can be detected and corrected successfully, if the number of continuous cycle slips is small, for example, less than 5.

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5. Modified weighted integer least squares estimations for GNSS integer ambiguity resolution
S. Jazaeri ; A. Amiri-Simkooei ; M. Sharifi

In this contribution, modified versions of Agrell, Eriksson, Vardy, Zeger (AEVZ) algorithms for integer ambiguity resolution of GNSS phase observations are presented. This modification removes many redundant mathematical operations of the AEVZ algorithm based on a recursive function. We also introduce G-based and H-based versions of AEVZ and its modification and compare the modified versions with the AEVZ method. Numerical results reveal that the H-based version of the modified algorithm performs the best. Therefore, it accelerates solving the high-dimensional weighted integer least squares problem. This results in faster integer ambiguity resolution.

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6. Effect of ionospheric delay modelling on long range VRS
A. Borka ; G. Even-Tzur

Relative GPS positioning based on VRS data makes it possible to reduce the observation time span needed for accurate positioning in long range distances from the reference station. The ability to derive an efficient and precise baseline solution with VRS data depends on the level of precision of the ionospheric assumption in the virtual observations. Increasing the ability to produce efficient VRS coverage will necessitate the formulation of a trustworthy technique for mapping the ionospheric delay at larger distances (hundreds of kilometres). In order to derive the minimal conditions needed for such a mapping technique, this study aims to explore how the accuracy of a VRS is impacted by the ionosphere, when it is produced at long range distances from the reference stations using different interpolation methods. Over the course of this research, several experiments that examined the precision of setting up the VRS in different scenarios were conducted, in order to determine the optimal method for mapping the ionosphere with the objective of providing long-range VRS service. The KRIGING method was found to be the most appropriate among the tested methods for mapping the ionosphere in the process of creating VRS observations. The ionospheric model that was created on the basis of KRIGING described the ionospheric delay’s temporal behaviour closest to the real variability as a function of time.

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7. Importance of probability levels for robustness analysis of geodetic networks
M. Yetkin ; M. Berber ; C. Inal

Robustness Analysis is a natural merger of reliability and strain and defined as the ability to resist deformations caused by the maximum undetectable errors. Internal reliability criterion describes maximum undetectable errors in observations, which would not be detected by Baarda’s statistical testing method (data snooping) based on the chosen Type I and II error probabilities. The non-centrality parameter is a function of probability levels and it plays an important role in Robustness Analysis. In this paper, it is aimed to show the impact of non-centrality parameter on the displacements and the relationship between the selected confidence level for confidence regions and threshold values in a geodetic network. For a geodetic network example, a GPS network is chosen and computations of displacements and threshold values (derived from confidence regions) have been carried out for both in-context and out-of context approaches. According to our results, the non-centrality parameter controls the magnitudes of displacements without affecting their relative behaviours. Statistically, lower probability levels are desired. However, if error probabilities are decreased, the non-centrality parameter increases. Since, the non-centrality parameter scales the displacements, a balance between both types of decision error is needed to obtain displacement values that are smaller than threshold values in order to reach a totally robust network at the required level of probability.

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8. Effect of subnetwork configuration design on deformation analysis
B. Erdogan ; S. Hekimoglu

Deformation analysis plays an important role for human safety, so investigating the reliability of the obtained results from deformation analysis is extraordinarily 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 there are outliers in the observations or displaced points in the deformation monitoring network, the results obtained from LSE are not optimal. LSE spreads the spoiling effects of deflecting from the assumed model to the residuals of good observations; also it spreads the effects of displaced points on the other estimated points coordinates that are not displaced. Therefore, obtained results diverge from their optimum values. In this study, the results of the CDA have been investigated in the Global Positioning System (GPS) network. To this aim three devices that could move horizontally were built and point displacements were simulated. Eight different scenarios at the regional GPS networks were carried out. The analyses of the GPS measurement were achieved for both whole network and subnetwork designs, so that the effect of the subnetwork design on the deformation analysis was investigated. The analyses of the GPS network show that subnetwork design has a more reliable result than whole network design.

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9. Optical flow algorithm as estimator of horizontal discrepancy between features derived from DEMs: rivers and creeks as case study
J. F. Reinoso ; C. León ; J. Mataix

DEMs (grid digital elevation models) are used for a broad spectrum of applications, some of which require deriving features such as drainage networks (rivers, creek, etc.). A precise positioning in the features taken from DEMs is necessary, but frequently DEMs are not homogeneous (e.g. the mapmaker sources vary, cell sizes differ), so that the expected precision fluctuates. Therefore, a measure to estimate the discrepancy between features built from different DEMs would be useful. In particular, we focus on the horizontal discrepancy (HD), which is the lesser studied discrepancy in the literature. Our approach is based in the optical flow (OF) algorithm, which has been used successfully in object movement detection in consecutive images or video records. We establish the analogy between an image and a DEM because both are composed of regular elements, pixels, and cells. The variation in the pixel value between two consecutive images is used by OF to compute movement. We use the variation in the DEM cell value (height) to apply the OF and to estimate the HD between rivers and creeks existing in our DEMs examples. In our study, OF proved to be a good estimator of HD when features were derived from hill and mountain terrain, but was not reliable when the terrain was almost flat. However, most studies in the research literature have indicated that nearly flat terrain poses the most difficulties in forecasting positioning errors. Therefore, we conclude that the OF is a good estimator of the HD between features derived from DEMs.

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Survey Review 46, No 334. January/February 2014

1. Effect of Thai Ionospheric Maps (THIM) model on the performance of network based RTK GPS in Thailand
T. Charoenkalunyuta ; C. Satirapod

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 investigation on the performance of NRTK with the aid of the THIM and the final GIM in various different reference station spacing, i.e. 10–20, 30–50, 50–60 and 60–80 km are compared. This investigation is performed using a large number of GPS observations (31 consecutive days) and all available Continuous GPS (CGPS) stations in the Central Plain region of Thailand. Test results indicate that the NRTK positioning performance with the aid of the THIM yields the best solutions when compared to the use of the final GIM and no model, especially in the case of the middle reference station spacings (i.e. 30–50 and 50–60 km spacing). Therefore, it can be concluded that the THIM can effectively mitigate the ionospheric bias in the NRTK mode in Thailand.

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2. GPS-structural health monitoring of a long span bridge using neural network adaptive filter
M. R. Kaloop ; D. Kim

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.

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3. The impact of the scale factor on the horizontal geodetic coordinates obtained by a three-dimensional similarity transformation
B.-G. Reit

In surveying the three-dimensional similarity transformation is commonly used for transforming horizontal geodetic coordinates between a three-dimensional reference frame and a two-dimensional horizontal geodetic datum. A problem that arises when the seven transformation parameters are given in beforehand is to implement the parameters with the correct values and signs. Assigning a wrong sign to the translations or the rotations will probably reveal itself, as the resulting errors in the transformed coordinates normally go up to several tens of metres. However, applying the scale correction with an erroneous sign will not always be discovered easily. In this paper, estimates are given of the errors in the transformed horizontal coordinates caused by an erroneous scale correction. Furthermore, it is demonstrated that an erroneous scale factor will have minor influence on the scale of the transformed horizontal coordinates. Finally an alternative transformation model is suggested which eliminates the need of a scale correction.

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4. Iterative algorithm for weighted total least squares adjustment
S. Jazaeri ; A. R. Amiri-Simkooei ; M. A. Sharifi

In this contribution, an iterative algorithm is developed for parameter estimation in a nonlinear measurement error model y−e = (A−EA)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 two-dimensional affine transformation in the case of diagonal and fully populated covariance matrices in both start and transformed coordinate systems.

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5. Robust Total Least Squares with reweighting iteration for three-dimensional similarity transformation
J. Lu ; Y. Chen ; B. F. Li ; X Fang

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 the gross errors to achieve the reliable solution.

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6. On ‘decorrelation’ in solving integer least-squares problems for ambiguity determination
M. A. Borno ; X.-W. Chang ; X. H. Xie

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-Lovász (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).

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7. Verification technology for topological errors in official databases with case study in Poland
M. Siejka ; M. Ślusarski ; M. Zygmunt

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.

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8. Proposed guidebook on established case law for land surveyors on property boundaries
D. O’Brien ; W. P. Prendergast

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 a ‘Guidebook’, this information would be of benefit for surveyors and property professionals in understanding the principles applied to previous cases and thus the principles to be applied in future cases to try to resolve boundary dispute incidences (before litigation). The rulings made in court can be employed as set principles for surveyors to follow when carrying out property boundary rectification and resolving property boundary disputes in the future.

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9. Land administration for housing production: analysis of need for interagency integration
M. E. Agunbiade ; A. Rajabifard ; R. Bennett

In most country contexts the activities of government land administration agencies, those dealing with the functions of land tenure, valuation, planning, and development, are disparate and lack harmonisation. This paper analyses the imperative for integrating these functions across and between government structures. An exploratory approach synthesising existing research and newly acquired empirical case study data from Victoria-Australia, and Lagos-Nigeria underpins the discussion. Drivers for interagency integration are exposed and discussed including: cost inefficiencies for actors in the development process, the effectiveness of planning enforcement, and redundancy in land information. Opportunities for integration are revealed through analysis of the land development process, land information infrastructures, and urban management policy.

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10. Book Review

Application of Linear and Nonlinear Models. Fixed Effects, Random Effects and Total Least Squares. Erik W. Grafarend and Joseph L. Awange. ISBN 978-3-642-22240-5.

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