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Survey Review 51, No 369. November/December 2019

1. Application of Indian space-based augmentation service on geospatial data collections in Sri Lanka
Thilantha Lakmal Dammalage

GPS Aided Geo Augmented Navigation (GAGAN) is the Indian Satellite-based Augmentation System, fully operational since 2013 with the objective of providing the accuracy and integrity required for civilian and aviation applications. This study investigates the usability of GAGAN service as an accurate, reliable and a cost-effective source of positioning and navigation for geospatial applications in Sri Lanka. Point, line and polygon features were collected under different challenging conditions to test the usability and potential accuracy of GAGAN. The average 3D positional accuracy enhancement over SPS is about 70 and 78% for GAGAN and DGPS observations, respectively. Similarly, the average GAGAN enhancement over SPS observation was 79% and 83% for linear and area measurements, respectively, and the improvement for DGPS was 86% for both feature types. This confirms that GAGAN can improve geospatial data collection accurately, almost similar to DGPS without a use of local reference station, or national CORS networks.

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2. Hybrid governance and land purchase strategies in a state-subsidised housing project in a rural South African town
Michael Barry & Lani Roux

Many of the estimated three million state-subsidised houses that South Africa has delivered to the poor in registered ownership since the end of apartheid in 1994 have changed hands off-register, creating cloudy titles. This is indicative of effective tenure administration being ranked below other policy goals without suitable strategies to address the shortcomings of granting ownership as the tenure form upfront. Interviews with residents, community leaders, officials, and land professionals indicate that buyers register transactions if the registration system is accessible, the family unit believes registration is useful, and that they are aware of the risks of off-register transactions. The South African land governance system is somewhat incoherent, with various hybrid official and unofficial arrangements. In this environment, community-based organisations (CBOs) may unwittingly encourage off-register transactions. It follows that continual title maintenance and CBO engagement are crucial in maintaining clean titles.

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3. Coastal and marine zone legislation within the concept of land management in Turkey
Volkan Baser & Cemal Biyik

In this study, the development of coastal and maritime zone legislation in Turkey was examined within the scope of e-government policy, and for a comparative analysis, the changes made in past legislation were included. For this purpose, the study determined the regulations in Turkey dealing with coastal and marine areas as found in different laws and statutory decrees, ordinances, communiqués, directives, general principles and in particular, the Constitution and the Civil Code. The institutions that carry out coastal and marine area activities were revealed by referring to the laws and to the ‘State Organization Database’. An activity matrix was established linking the laws and their associated activities. The maritime borders of Turkey were presented in terms of international law and evaluations were made on the findings.

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4. Robust acquisition at GPS receivers in unsafe locations using complex wavelet transform
M. Moazedi, M. R. Mosavi & A. Sadr

Growing importance of Global Positioning System (GPS) applications in various fields, leads many researches to the security of GPS systems and investigation of eventual perturbations in them. One of the most important intentional interferences is spoofing. This work presents an anti-spoofing method based on complex wavelet transform (CWT). Fake satellites are omitted and then understrength satellites due to spoofing are identified. The results of investigation suggest that the proposed CWT based estimation and extraction method is better than relatively simple wavelet transform. The suggested filter is applied in the Intermediate Frequency signal. Cross-validation technique is used for automatically identifying wavelet signal layers. The proposed method has been implemented on different collected datasets. Software GPS Receiver has been used to implement and validate the developed anti-spoofing technique because it is more flexible and economical compared with usual hardware receivers.

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5. Partial GNSS ambiguity resolution in coordinate domain
Shengyue Ji, Rongyao Du, Wu Chen, Zhenjie Wang, Kaifei He & Zhixi Nie

Traditionally, if full ambiguity resolution is not successful, partial ambiguity resolution (PAR) will be tried. However, identifying which subset of ambiguities to fix is not easy and is still an open problem. Since the actual purpose of most applications is positioning, rather than fixing all or part of the ambiguities, in this research, we are trying to bypass the problem of identifying which subset of ambiguities to fix and provide a partial solution in the coordinate domain for the bias-free case. The basic idea is that with a user-defined failure rate, we can find a group of ambiguity candidates and each will provide one position. The partial solution is constructed based on these positions together with an indicator to show its maximum positioning error with user-defined reliability. In order to meet various user requirements, different kinds of partial solutions in coordinate domain are proposed. Different from the traditional PAR methods, the new method still works with all the ambiguities (i.e. the complete vector), but works with the different possible values that the complete ambiguity vector may take. The validness and applicability of the proposed partial solution are demonstrated-based practical BeiDou triple-frequency observations. Numerical results show that some partial solutions can be more accurate, while others can meet higher reliability or integrity requirement.

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6. Comparing GPS positioning errors derived from GAMIT/GLOBK and Bernese GNSS software packages: A case study in CORS-TR in Turkey
Seda Cetin, Cuneyt Aydin & Ugur Dogan

Global Navigation Satellite System (GNSS) processing software packages such as GAMIT/GLOBK, Bernese, GIPSY/OASIS etc., have an important role in high-precision GNSS studies. For a single GNSS session, they result in Formal Error (FE) rather than positioning accuracy because it may not be possible to incorporate the correlations in the GNSS data properly into the stochastic model of the estimation procedure. Therefore, a GNSS network used for high-precision studies should be measured repeatedly in different sequential days to have repeatabilities of positions to be used for representing the RMS errors of positioning. This contribution investigates the relationship between the FE and RMS error of Global Positioning System (GPS) positioning for GAMIT/GLOBK (V10.6) and Bernese (V5.2) software packages. For this purpose, seven days of GPS observations in six different sub-networks consisting of totally 36 Continuously Operating Reference Station (CORS) network stations in Turkey are used. The sub-networks were selected such that they were distributed homogenously throughout Turkey. The GPS observations were processed in the ITRF2008 reference frame using both GAMIT/GLOBK and Bernese software packages. Daily repeatabilities of North, East and Up coordinates of each station obtained from two software packages are nearly the same. However, their FEs are very different. GAMIT/GLOBK gives bigger FEs while Bernese results in too smaller FEs compared to their RMS errors of positioning. A linear relationship exists between the average of seven days FEs and the RMS errors for both software packages. This relationship is defined as the ‘Scale Factor (SF) = RMS/FE’. It is shown that a unique SF for the corresponding software package can be given as the mean value of the SFs associated with all points used in the study. According to our analysis, the mean SF in the region is 0.38 and 3.82 for GAMIT/GLOBK and Bernese, respectively.

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7. Regional spatio-temporal zenith tropospheric delay modelling using independent component analysis
Wujiao Dai, Huineng Yan, Biyan Chen & Bin Liu

Accurate modelling of the zenith tropospheric delay (ZTD) is of significant value in many applications such as Global Navigation Satellite System (GNSS) positioning. Most ZTD models require meteorological parameters, which are difficult to obtain in many practical applications. Though some empirical models can predict the ZTD values without meteorological parameters, their performances are usually unsatisfactory. To overcome these issues, a spatio-temporal ZTD modelling method based on independent component analysis (ICA) without using meteorological parameters is proposed in this study. In this method, multi-dimensional ZTD data can be reconstructed by several temporal independent components and corresponding spatial response values. Regional ICA ZTD models for Hong Kong, UK and China mainland were established using the daily GNSS ZTD data. Results show that ICA regional ZTD models perform better than Saastamoinen, UNB3m and GPT2w models in general. The proposed ICA ZTD modelling method is proven to have advantages of simpler modelling process, fewer model parameters and higher applicability. This study suggests that ICA is very promising in modelling spatio-temporal variation of ZTD, especially for a region with dense GNSS network.

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Survey Review 51, No 368. September/October 2019

1. Defining the unitary types of urban uses: urban uses, land uses and land-use zones
Ioannis A. Pissourios & Alexandros Ph. Lagopoulos

It is clear that urban planning is not a theoretical science, but an applied field. However, this does not imply – or justify – the lack of an analytical field that would lay the scientific foundations of urban planning and guide planning practice. This field, which we call urbanology, must consist of a theory of urban uses, since the latter constitute the foundation of all international planning practice. As part of the process of formation of this theory, the present paper focuses on defining the unitary types of urban uses, that is, the units which constitute the smallest, not further divisible typological elements of the organisation of urban space. We begin with the definitions of the basic concepts of urbanology, namely: urban use, unitary type of urban use, land use and institutionalised land-use zone. We then attempt to specify the criteria for determining the unitary types of urban uses, which when applied to Greek space leads to the specification of 330 types of urban uses. We also demonstrate that this work does not only concern the analysis of urban space and the survey stage of urban planning, but also planning proposals and legislation.

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2. Evaluation of global geopotential models: a case study for India
Ropesh Goyal, Onkar Dikshit & Nagarajan Balasubramania

This paper aims to identify most suitable global geopotential model (GGM) for India, by comparing 15 GGMs developed through 1996 to 2017. The GGM derived geoid undulation values are compared with the geometrical undulation values obtained from GNSS/levelling data on Indian vertical datum. A correction term is added to the computed GGM derived geoid undulation value after fitting three-, four-, five- and seven-parameter models to account for bias and tilt between local geometric Indian vertical datum and global gravimetric vertical datum. The results indicate that EGM2008 model is the best GGM available for India with root-mean-square error (RMSE) of 0.28 m, without model fitting. However, after considering the systematic errors in the two datums with seven-parameter model, GECO GGM has shown significantly better results with RMSE of 0.19 m for India.

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3. A method for drawing vertical curve in longitudinal profile in road project
Hüseyin İnce & Nuri Erdem

In road projects, there is a difficulty in drawing tangent points of the calculated vertical curve, turning point and intermediate points due to horizontal and vertical scale differences. This problem is brought about by the fact that proportional relationship between the two different scales is not known for a length with a certain slope in longitudinal profile. This study proposes a method to eliminate this problem. It also gives an example and discusses the findings.

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4. Reduction of measurement data before Digital Terrain Model generation vs. DTM generalisation
Wioleta Błaszczak-Bąk, Marian Poniewiera, Anna Sobieraj-Żłobińska & Michał Kowalik

Modern data-acquisition technologies provide large datasets. Such datasets are often cumbersome for rational processing, and their processing is time consuming. Therefore, there are several methods that can enable the reduction of the dataset size. One of them is generalisation of the Digital Terrain Model (DTM) or the reduction method within the initial processing of measurement data. Another method can be the Optimum Dataset (OptD) method. This paper presents two approaches towards decreasing the Light Detection and Ranging dataset. The first approach is based on the process of DTM generalisation, the second one is based on the application of the OptD method. The reduced datasets were used for isoline map creation depicting the overflow land in open-pit mining. It was proved that the reduction needs to be planned deliberately and that the degree of reduction should be performed in a way that allows to maintain the characteristics of the terrain.

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5. The use of GIS tools for sustainable management of municipal housing stock in Poland
Agnieszka Dawidowicz, Andrzej Muczyński & Marek Emanuel Pacholczyk

The management of social housing stock by balancing the housing needs of local communities plays a crucial role in the sustainable development of urban municipalities. In the present study, the management of municipal housing stock (MHS) was evaluated for compliance with sustainability principles using GIS tools. Special attention was given to the spatial, technical, tenure-related and organisational aspects of sustainable MHS management. The importance of spatial data and spatial analyses for assessments of MHS management was demonstrated. The research was based on a case study analysing MHS management in the Olsztyn municipality.

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6. Analysis of higher-order ionospheric effects on GNSS precise point positioning in the China area
Yaozong Zhou, Cuilin Kuang & Changsheng Cai

Higher-order ionospheric error may reach several millimetres in the case of high ionospheric activity, which affects some high-accuracy applications, such as crustal movement monitoring, earthquake disaster prediction, plate motion monitoring and coordinate frame maintenance. However, accounting for higher-order ionospheric error is not yet a common strategy for regional global navigation satellite system (GNSS) network data processing. This study investigates the higher-order ionospheric effects on precise point positioning (PPP) in the China area with GNSS data selected from some IGS stations and some CMONOC stations. The Bernese GNSS software was used to calculate the effects of higher-order ionospheric error on the PPP estimated coordinates. The numerical results show that higher-order ionospheric positioning errors become larger as the station latitude decreases or the ionospheric activity increases. In addition, the positioning errors in the north direction are larger than those in the east and up directions and may reach 6 mm in south China.

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7. Assessing a new velocity field in Greece towards a new semi-kinematic datum
S. Bitharis, N. Papadopoulos, C. Pikridas, A. Fotiou, D. Rossikopoulos & V. Kagiadakis

Greece has always been an interesting study area for the geodesists due to its intense geodynamic behaviour. Especially, the exploitation of a modern geodetic velocity field using GNSS becomes a crucial requirement for geodetic purposes. The main aim of the present study is the assessment of a modern geodetic velocity model. This procedure is based on the unification of various reference frames, implemented from individual extended GNSS campaigns in different epochs with the effective involvement of the Hellenic Military Geographic Service. The implementation of geodetic velocities in the inhomogeneous Greek velocity field improves significantly the reliability of transformations, more than 60% with respect to the horizontal component, applying a vice versa time shift to a common epoch. We also emphasise the necessity to adopt a velocity model in order to process regional GNSS networks and therefore to establish a modern semi-kinematic reference frame in Greece.

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8. Performance analysis of GLONASS integration with GPS vectorised receiver in urban canyon positioning
Amir Tabatabaei & Mohammad-Reza Mosavi

Urban-canyon positioning encounters many problems such as successive attenuation and even blocking of the signals. Vectorised receiver is a solution in which stronger signals aid weak and blocked ones to be tracked and reacquired. On the other hand, limited accessibility to the sky makes trouble in the performance of navigation filter. As the result, integration of satellite-based positioning systems is suggested to increase the number of visible satellites in the receiver view. In this paper, the architecture of an implemented GPS-combined-GLONASS Vectorised Receiver (GGVR) in a software platform is explored and its advantages rather than a GPS-only Vectorised Receiver (GVR) are demonstrated analytically. Experimental tests in different static and dynamic scenarios are also included. The results show that in the urban-canyon trajectory where the GVR has only 80% availability, the GGVR positioning solution is 100% available in the whole movement duration.

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9. Experimental research on daily deformation monitoring of bridge using BDS/GPS
Jian Chen, Dongjie Yue, Zhiqiang Liu, Chang Xu, Shaolin Zhu & Hao Chen

Multi-constellation will greatly improve the accuracy, completeness, effectiveness and continuity of the Beidou Navigation Satellite System (BDS)/Global Positioning System (GPS) bridge health monitoring. Firstly, the reliability of the monitoring results was ensured by using the dual-base station mode. For the dynamic post-processing mode, the empirical mode decomposition–wavelet transform coupled model was used to reduce the noise of original coordinate sequences. Finally, the self-programmed software was adopted to solve the observation data of 48 consecutive hours and thus analyse the daily deformation characteristics of the bridge. The experiment results show that under the good conditions of the satellite number and their geometric distribution, the monitoring results of the BDS/GPS combination system were in good agreement with the results of the GPS single system and BDS single system. However, in the complex environment of the bridge, especially when the signals were severely affected, the advantages of using the BDS/GPS combination system for deformation monitoring were more obvious.

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Survey Review 51, No 367. July/August 2019

1. Minimal Detectable and Identifiable Biases for quality control
D. Imparato, P. J. G. Teunissen & C. C. J. M. Tiberius

The Minimal Detectable Bias (MDB) is an important diagnostic tool in data quality control. The MDB is traditionally computed for the case of testing the null hypothesis against a single alternative hypothesis. In the actual practice of statistical testing and data quality control, however, multiple alternative hypotheses are considered. We show that this has two important consequences for one's interpretation and use of the popular MDB. First, we demonstrate that care should be exercised in using the single-hypothesis-based MDB for the multiple hypotheses case. Second, we show that for identification purposes, not the MDB, but the Minimal Identifiable Bias (MIB) should be used as the proper diagnostic tool. We analyse the circumstances that drive the differences between the MDBs and MIBs, show how they can be computed using Monte Carlo simulation and illustrate by means of examples the significant differences that one can experience between detectability and identifiability.

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2. Analysis of free image-based modelling systems applied to support topographic measurements
José Miguel Caldera-Cordero & María-Eugenia Polo

The image-based modelling systems create 3D models of objects using a set of overlapping photographs. Several applications are available that do not require a user expert or expensive equipment. In this paper, four free systems were applied in two cases: ReMake, which is a freemium software, CMP Web Service and Arc 3D, which are free web services, and Visual SfM, which is a free software. The purpose of this study is to evaluate the applications that support topographical measurements and to assess the potential for their use in accurate modelling. The results show that these systems can be an auxiliary technique for surveyors and can provide an advantage in some cases.

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3. The INSPIRE directive: some observations on the legal framework and implementation
George Cho & Joep Crompvoets

The observation that spatial and environmental data relating to specific locations or geographic areas in the European Union (EU) have been difficult to find online is undisputed. Whether the EU INSPIRE Directive of 2007 which establishes an infrastructure to enable the sharing of spatial data and services to support European and national environmental policies will achieve its objectives is a topic of debate. The INSPIRE Directive was conceived and implemented to address identifiable challenges relating to environmental policies and data. Before the complete implementation of the Directive, it may be necessary to reflect on what progress have been achieved at a legal and policy level. The central argument of this paper is that legal and policy issues may have hindered the rapid and smooth implementation of the Directive. The implementation of the legal framework of the Directive provides salutary lessons. Evaluation reports from the European Commission and the four case studies demonstrably paint an encouraging future. The conclusion is that INSPIRE should foster good governance, use and sharing of environmental data and information for the common good of all Europeans.

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4. Automatic and accurate passive target centroid detection for applications in engineering geodesy
Mohammad Omidalizarandi, Jens-André Paffenholz & Ingo Neumann

A novel automatic and accurate passive target centroid detection approach is proposed and developed which has numerous fields of applications, such as in engineering geodesy, photogrammetry, robotics and navigation. It is robust and reliable with respect to poor environmental conditions, such as low lighting, dusty situations and skew angle targets. This research is conducted in two parts. First, an optimal target selection and its accurate, automatic and fast centroid detection are performed. Afterwards, two case studies of the proposed approach are presented for automatic target pointing by means of the telescope camera of an image assisted total station (IATS) (here Leica Nova MS50 MultiStation) and automatic target measurements for a digital camera (here Nikon D750). The results show that a circular target with a line pattern consisting of four intersected lines is an optimal pattern. The accuracy of the proposed method varies depending on the image resolution and distances to the objects. We performed experiments for distances between 1.6 and 28 m for the IATS and achieved sub-millimetre accuracy.

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5. Spatial information recovery in the desert using LMS-based geodetic network adjustment
Eva Stopková

This paper describes the local coordinate system recovery at the archaeological site Tell el-Retaba (Egypt), without any GNSS technology or the positioning in an official reference frame available. Completely destroyed control points were restored using geodetic network adjustment based on terrestrial observations and multi-epoch solution of the Least Mean Square models, and transformed into the original local coordinate system using identical points located on ancient mud-brick structures in former trenches. However, current and past measurements of excavated objects fit almost perfectly. Statistical and empirical tests indicate that the outliers correspond with measurements in harsh desert conditions.

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6. On the use of between-baseline differenced and instantaneous RTK positioning while using simultaneous GNSS measurements
Julian Thom, Robert Odolinski, Luke McDonald & Paul Denys

The single-baseline real-time kinematic (RTK) model has been used over the past few decades for precise positioning. In this contribution, we investigate the performance of the between-baseline differenced (BD) instantaneous RTK model derived by taking the difference between two simultaneously measured single-baseline RTK positions. The BD RTK model can be more efficient to compute since one only needs to take the difference between three baseline coordinates of the receivers. Comparisons are made between the two models while collecting GPS, BDS, Galileo and QZSS data for baseline lengths ranging from 0 to 29 km. We show that re-estimating the single-baseline and computing the BD RTK solutions will give identical results, as long as the satellite positions in view do not become significantly different. Finally, we demonstrate that the success rate for a long BD RTK baseline can increase in comparison to using single-baseline RTK, provided it is determined from shorter baselines.

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7. Accuracy assessment of speed values calculated from GNSS tracks of roads obtained from VGI
Antonio Tomás Mozas-Calvache

This study describes the results of an assessment of the accuracy of relative measures between two points, and more specifically of speed values, obtained from Global Positioning Satellite Systems (GNSS) tracks acquired by contributors of Volunteered Geographic Information (VGI). The VGI does not usually include information about the positional accuracy of the trackpoints neither of speed values derived from these positions. Consequently, the assessment is based on a field test that consisted of a vehicle which travelled a highway with a set of Global Positioning System (GPS) devices like those commonly used by VGI contributors. These devices captured positions of trackpoints with a time interval of 1 second. Additionally, a more accurate geodetic RTK–GNSS receptor controlled these positions. The paper describes the methodology employed, taking into account several parameters such as the acquisition time interval, the accuracy of control positions, etc. The results have demonstrated the viability of the methodology applied, the possible use of VGI in order to determine the speed values of the trackpoints and the possible improvement in the accuracy achieved with the increase of the distance between trackpoints (and as a consequence of time interval), but with the disadvantage of a reduction in the quantity of trackpoints. Thus, several values of time intervals have been suggested, considering the accuracy required.

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8. Landslide monitoring analysis of single-frequency BDS/GPS combined positioning with constraints on deformation characteristics
Dongwei Qiu, Laiyang Wang, Dean Luo, He Huang, Qing Ye & Yunlong Zhang

In order to optimise the selection of landslide monitoring points and save the cost of monitoring, a geological constitutive model was constructed by using 3D laser scanning and geological borehole data to simulate the relationship between rainfall and deformation. Thus, the main occurrence area and maximum deformation of the landslide were determined. Aiming at the deficiency of the single-epoch redundancy of the single-frequency GNSS receiver and the poor accuracy, this paper proposes a single-frequency BDS/GPS combined positioning and monitoring scheme with constraint of deformation features to restrict the search range of single-frequency ambiguity, obviously increase the ambiguity fixed success rate and then improve the BDS/GPS positioning accuracy. By contrast experiments, the landslide area obtained by numerical simulation basically matches with the on-site landslide area. The BDS/GPS combined positioning with constraint is consistent with the deep displacement changes, which can well reflect the displacement of the landslide body and make an early warning of disasters.

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9. Adjustment options for a survey network with magnetic levitation gyro data in an immersed under-sea tunnel
Ji Ma, Zhiqiang Yang, Zhen Shi, Chenchen Liu, Haiqing Yin & Xiuzhen Zhang

Since gyro azimuths are affected by the complex environmental factors that are present in underground spaces, the adjustment model should take this into account. In general, gyro azimuths are considered to be errorless or equal precision observations in the adjustment model, which leads to the overestimation or underestimation of the weight of the gyro azimuths. To improve the precision of underground networks, measured with a magnetic levitation gyroscope, an adjustment for the survey network with individually weighted gyro observations is proposed. The proposed method was tested on an equivalent mock-up network of the tunnels associated with the Hong Kong-Zhuhai-Macau Bridge. The lateral breakthrough error and lateral standard deviation at the breakthrough point were calculated and compared. Our result shows that the lateral breakthrough error was 4.8 mm with the precision change ratio of 64.5% which suggested that the proposed method is able to improve the precision of the breakthrough point.

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Survey Review 51, No 366. May/June 2019

1. Efficiency of OPUS-RS solutions
A. D. Dogru, H. Duman, D. U. Sanli & M. M. Berber

Today rapid-static GPS is an alternative surveying technique among other fundamental GPS surveying methods such as real-time kinematic and static GPS. It usually finds application areas in engineering surveying and monitoring of ground deformation for example landslides. Web-based GPS software such as OPUS-RS which was developed by the National Geodetic Survey (NGS) promoted further the use of the technique. NGS also provides its users the obtainable accuracy of the OPUS-RS derived solutions. Minimum 15 min of GPS data is recommended for rapid-static positioning and the accuracy is given accordingly. In this study, we go beyond the typically recommended 15 min observations and examine the accuracy variation of rapid-static OPUS positioning solutions over 8–118 min interval. Seven Continuously Operating Reference Stations from the US are selected, and their data are segmented into the above-mentioned shorter sessions. Statistical analyses of the CORS stations revealed that solutions from 15 min or shorter sessions contain outliers, and this degrades the efficiency of the technique. By extending the typical 15 min observation length up to 60 min perfectly eliminates the outliers, and the accuracy on the average is improved by about 5–20 mm for horizontal and about 25 mm for vertical components.

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2. Ability of GPS PPP in 2D deformation analysis with respect to GPS network solution
C. Aydin, S. Ö. Uygur, S. Çetin, A. Özdemir & U. Dogan

GNSS networks play an important role in monitoring the displacements, movements and deformations of the Earth’s crust and engineering buildings. In this study, we examine how GPS Precise Point Positioning (PPP) is able to determine the horizontal deformations with respect to the GPS network solution. For this purpose, 7 days data of 12 Continuously Operating Reference Stations (CORS) in Turkey (CORS-TR), located in the western part of Turkey, are considered. The Bernese (v5.2)-derived coordinates over 7 days and the ones from four free online PPP services (CSRS, GAPS, APPS, Magic-PPP) are compared using the Bursa-Wolf coordinate transformation model. The errors from these transformations are used to define the RMS values of the PPP solutions in the local coordinate system. These values are relative to the GPS network solution. This fact leads to analysing how the PPP solutions are able to determine the horizontal deformations with respect to the network solution. From many experiments, in which the displacements belonging to the PPP solutions are simulated relative to the network solution, it has been shown that several ppm extensions or contractions may be determined using the free online PPP services. Therefore, we conclude that the online PPP services studied here may be used in 2D deformation studies as an alternative to the GPS network solutions.

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3. Comparative study of using different ionosphere models in Thailand for single-frequency GNSS users
Khunphut Prakanrattana & Chalermchon Satirapod

An ionosphere layer makes inaccurate global navigation satellite systems (GNSS) signal. The ionosphere layer contains free electrons delaying the speed of GNSS signals. A suitable selection of ionosphere model is very useful to eliminate this inaccurate GNSS signal. This article presents a comparative study by applying various ionosphere models in Thailand including: Klobuchar model, Global Ionosphere Maps, Ionosphere Model from Quasi-Zenith Satellite System and local ionosphere model. The local ionosphere model is generated from GNSS observations at with the use of locally available GNSS tracking stations by the Bernese GPS software 5.0. Coordinates derived from the above-mentioned models were compared and statistical tests in two observed scenarios; namely, single-frequency data and ionosphere-free linear combination from dual-frequency data. These experiment results proved that applying the local ionosphere model to the estimation produces the most accurate positioning results. They are similar to the results obtained from an ionosphere-free linear combination, but with significant differences.

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4. Reliability analysis for non-distorting connection of engineering survey networks
Witold Prószyński & Sławomir Łapiński

A non-distorting network connection is a complex procedure consisting of a local network adjustment and a subsequent Helmert transformation into the connection points without changing the scale, i.e. isometry transformation. Since a joint adjustment model proposed for this connection in the earlier publication did not turn out sufficient to create a detailed reliability description for the whole procedure, reference had to be made to the original two-step approach. The reliability measures for a joint model and for each of the above mentioned procedural steps of the connection are being analysed. It is shown that the reliability description as based on indices obtained from the joint model should be supplemented with the indices from the two-step model. A specific property of the connection concerning mutual controllability of coordinates of the connection points is formulated on the basis of the Helmert transformation. The theory is illustrated on some numerical examples.

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5. An analysis of the national spatial data infrastructure of Iran
A. Kalantari Oskouei, M. Modiri, A. Alesheikh, R. Hosnavi & M. A. Nekooie

Spatial data infrastructure (SDI) assessment is essential for guiding development, implementation, maintenance and improvement. This paper examines the development status of Iran’s national spatial data infrastructure. The framework of the research is constructed based on a literature review, survey and SDI readiness model. The comparative analyses reveal that Iran’s SDI readiness index is not well developed, mainly due to the relatively low level of development of the organisational, human resources and information factors. Additionally, it seems that there is a link between the SDI readiness index and the national income of countries. Countries with a higher SDI readiness index than Iran tend to be high-income countries. As a consequence, the research suggests that achieving a successful national SDI in Iran requires the development of a comprehensive set of infrastructures: most importantly, policy, legal, cultural, human resources and institutional infrastructures.

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6. Two points registration algorithm for terrestrial laser scanner point clouds
Ahmed Abdelhafiz & Taher Hassan

Despite all modern techniques in registering terrestrial laser scanner point clouds, registration of multiple scan positions is still a crucial issue, especially in large projects. Processes like the detection of corresponding points in scans and placing targets in fields consume a lot of effort, time and money. Three points are the minimum number of common points required for registration. In this work, a new two points registration (TPR) algorithm is developed to register terrestrial laser scanner point clouds using only two common points automatically. Decreasing the number of the required common points to two points reduces one-third of the registration work in both field and laboratory. An accuracy assessment study is then performed to compare the registration accuracy of the developed algorithm and the traditional algorithm employing both the time of flight laser scanner and the phase shift one. The results show that the accuracy of the two algorithms is approximately equal within the considered point clouds accuracy in both cases.

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7. Is there still a (land) surveying profession?
B. J. Coutts & M. S. Strack

Land surveying has grown from a technical occupation into a profession. The criteria for what constitutes a profession, as distinct from a trade, is explored. Surveying meets criteria. It is maintained that the history of surveying can be seen as having two distinct paradigms. The question is raised as to whether it is entering a third paradigm based on technological developments of the last half-century but answered the in the negative. The introduction of the term ‘geomatics’ is considered and is found to have failed to meet the advances expected of it. It is maintained that the descriptor ‘land’ has out lived its usefulness. It is proposed that the adoption of the term ‘geospatial’ surveyor, by stealth rather than statute, is likely to achieve what geomatics did not. It is noted that this is already happening in the United Kingdom and in Australia similarly.

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8. Ellipse-fitting algorithm and adaptive threshold to eliminate outliers
L. Zhang, X. Cheng, L. Wang & X. Cheng

Terrestrial laser scanning is widely applied in many fields owing to its characteristic of rapid acquisition of massive 3D point data. It provides a new way to obtain the cross-section data of metro tunnels for deformation analysis. However, the data contain many outliers, such as pipe and bolt holes, and manual filtering of unwanted points is relatively onerous. Therefore, an ellipse-fitting algorithm based on residual p-norm minimum is proposed to deal with the outliers. Then, an adaptive threshold selection method is introduced for outlier elimination. The remaining valid data are utilised to calculate the deformation after data processing. The experiments validate that the p-norm minimum is more robust than the least-squares algorithm, and the application of an adaptive threshold allows the algorithm to clearly distinguish the outliers. This research provides a reference for the monitoring of subway tunnel deformation.

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9. Monitoring surveying students’ environmental attitudes as they experience higher education in New Zealand
Mick Strack, Kerry Shephard, Tim Jowett, Samantha Mogford, Sheila Skeaff & Miranda Mirosa

We investigate the environmental attitudes (EA) of New Zealand’s land surveying students and how they change during a four-year programme. We implemented a multi-cohort survey and developed a longitudinal statistical model of change. Findings suggest that although the EA scores of groups of students vary at different times within and between cohorts, there are no significant general trends when genders are combined. But females tend to start their studies with higher mean EA scores than males and this difference declines overtime. This occurs consistently across the four cohorts studied. This is discussed in relation to women’s role within the profession.

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10. Assessment of land ownership fragmentation by multiple criteria
Zlatica Muchová

In this contribution, a simple way of assessing land ownership fragmentation by evaluating land consolidation projects on the basis of multiple criteria is proposed. Obviously, for the criteria that describe fragmentation directly (number of plots, co-owners per plot and plots per owner), minimum values are regarded as favourable. Average size of the plot in a low-fragmentation situation is, of course, higher and is an expected benefit. Distances in spider/radar plots (star coordinates) or the Euclidean distance from an ‘ideal point’ are used as well to measure the (de)fragmentation. Post- and pre-consolidation ratios reflect the changes. Rankings based on the calculated values help to identify problematic cases. Thus proposed system takes into account not only the ownership fragmentation, number and size of plots, but also the co-ownership shares. Its application is demonstrated using the data on 50 finished projects of land consolidation in Slovakia.

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11. The analysis of settlement network’s dispersion using Ward’s taxonomy method
Barbara Prus & Marta Szylar

Buildings together with related constructions and also with facilities of technical infrastructure create settlement units. A settlement network is made of interconnected settlement units that create the functional structure of the settlement network. After the period of the political transformation in 1989, changes in settlement systems have been observed. The number of buildings has increased, their function, shape, colours and mutual arrangement have changed. The aim of the paper is to analyse settlement units paying special attention to the buildings’ dispersion and their division into the groups of uniform objects (units). The similarity of settlement units (registration ranges) in regard to the concentration of residential housing and productive development for agriculture is determined. Information about buildings’ location and their function is taken from the Database of Topographic Objects BDOT10k acquired from the Centre of Geodesic and Cartographic Documentation. The level of building complex concentration is determined by means of the concentration index on the plane. Advanced techniques of geoprocessing are used in the paper. Units’ similarity is determined by means of the method of numerical taxonomy using the agglomerative combinatorial Ward method. The results of the survey indicate the fact that the level of buildings’ dispersion is influenced not by the amount of buildings in particular ranges but their mutual arrangement and its level in space. However, the ranges with the smaller area are characterised by the lower dispersion level which responds to the higher value of the concentration index. High buildings’ concentration is a characteristic feature of not only the close vicinity of cities. The analyses proved the irregular arrangement of units with various levels of buildings’ concentration without implication to the hierarchy of the structure of the functional settlement network. So, the buildings’ concentration is of chaotic character which confirms the high entropy of the settlement network in Poland.

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12. Erratum and addendum to the paper ‘A new ZTD model based on permanent ground-based GNSS-ZTD data’, Survey Review, 2016, 48(351), 385–391
M. Ding & W. Hu

We correct some errors and give some more research for our paper published in Survey Review, 2016, 48(351), 385–391. This note is a correction owing to the use of the questionable surface meteorological measurements of the International GNSS Service (IGS) and also gives more sufficient studies to validate our method due to our inadequate study. Numerical weather model values of surface meteorological data were used to check the IGS surface meteorological measurements and long-time zenith tropospheric delay values at 76 radiosonde stations in Russia and near Russia were added as test data. Revised, updated and additional results were shown and analysed, which provide more evidence to show that the new proposed ISAAS model has a better accuracy than the Saastamoinen in Russia.

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Survey Review 51, No 365. March/April 2019

1. Human rights in tension: guiding cadastral systems development in customary land rights contexts
Simon Hull & Jennifer Whittal

Land reform in South Africa has failed to meet its objectives. The intended beneficiaries often do not have their land reform needs met. Failures may be attributed to multiple sources. We propose a conceptual framework to assist governments conducting land reform projects. It draws on aspects of human rights, good governance, and pro-poor policy. Existing frameworks are combined with these aspects to derive the conceptual framework. By using the framework, development projects in South Africa and similar contexts may become more Successful, Sustainable, and Significant. The paper holds interest for land tenure and cadastral systems researchers and developers.

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2. Geodetic network design and data processing for Hong Kong–Zhuhai–Macau link immersed tunnel
Shengxiang Huang, Guanqing Li, Xinpeng Wang & Wen Zhang

The immersed tunnel is composed of elements which are prefabricated elsewhere and floated to the tunnel site to be sunk into the prepared trench. Each element and the closure joint must line up exactly for the watertight gaskets to seal properly. For the construction of extra-long immersed tunnel, particular care should be taken in the perspective of geodetic control. Therefore, the design and implementation of the geodetic basis and hierarchical surface control networks are described. To decrease the influence of lateral refraction and to improve the configuration strength and increase the number of redundant observation compared with traverse, the design of underground surveying network named duo-linear joint chain is presented. The data-processing methodology, including outlier detection for excluding outliers from observation and variance component estimation for realistic precisions of observation, is described. Hong Kong–Zhuhai–Macau immersed tunnel surveying data are analysed and the performance of the geodetic networks and data processing methodology is demonstrated.

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3. Method for an automatic alignment of imagery and vector data applied to cadastral information in Poland
J. J. Ruiz-Lendínez, B. Maćkiewicz, P. Motek & T. Stryjakiewicz

Nowadays, an important problem in combining vector data and imagery is that they rarely align. This problem can become particularly acute in the case of cadastral systems. In this study, and as part of the partnership between the Universities of Jaén and Adam Mickiewicz (Poznań), we provide a methodological proposal to assess the conflation procedures between cadastral vector data and imagery, improving the alignment between both data sets. To do this, we use an automatic alignment algorithm which detects road intersections from both data sets as control points by using image texture characterisation. With this method, we first train the system on the imagery to learn the road texture distribution, then we can obtain its segmentation according to its texture, and finally the system locates road intersection points. The last step is to align vector data and imagery by using different techniques. This algorithm is based on an earlier one, detailed in [Ruiz, J.J., Rubio, T.J., and Ureña, M.A., 2011b. Automatic extraction of road intersections from images in conflation processes based on texture characterization. Survey review, 43 (321), 212–225.]. However, in the updated version we have solved the problem of not-well-defined intersection points, resulting in a substantial increase in the number of intersection points employed for the final adjustment to align both products and in a reduction of the computation time. On the other hand, the positional uncertainty assessment of parcel boundary lines both before and after applying our alignment procedure between them is provided. With regard to the experimental results, in the case of Polish cadastral data this procedure allows for significant improvement in the alignment between imagery and cadastral parcels boundaries.

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4. Domain model for cadastral systems with land use component
Đorđe Pržulj, Nataša Radaković, Dubravka Sladić, Aleksandra Radulović & Miro Govedarica

Well-structured and organised cadastral records and cadastral maps are a prerequisite for improving land administration services. In recent years, numerous problems and issues associated with cadastral data have been encountered in Serbia and attempts to overcome these problems have been made. The integration of land registry data with cadastral data containing land use component usually results in inconsistencies in land administration databases. To address this problem, an appropriate domain model has been developed using the Unified Process methodology and considering the land administration domain model and other ISO 19000 standards. Examples of verifying land administration data integrity in relational and object-oriented data models are presented.

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5. An alternative method for expropriation for lane-like projects in planned area: a case study from Trabzon in Turkey
V. Baser, B. Uzun & V. Yildirim

This study focuses on the Tanjant Road in Trabzon, in which public authorities expropriated a lot of parcels together with buildings then destroyed all of them and then finally finished the road. If Tanjant road was opened in accordance 3194/18th article, contribution rate was to be 39%. It is seen that contribution rate to be curtailed from the adjusted cadastral parcels has fallen to 18% on 337 cadastral parcels after the expropriation for Tanjant road. If LR was applied, the road field to be expropriated would be met via the area acquired from the LR, thanks to contribution rate. In both practices, it is aimed that keeping arrangement area wide; the benefits and problems Tanjant road and article 18 have brought are distributed to a wide area. It is seen that expropriation costs are met free of charge in inner-city route with LR.

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6. Data model design for qualified natural-protected area in Turkey
Merve Özlem Saralioğlu, Osman Demir, Yakup Emre Coruhlu & Ekrem Saralioğlu

Natural protected areas (NPAs) in Turkey are generally determined on standard topographic maps at a scale of 1/25 000, as opposed to cadastral border detection measurements. This situation generates a variety of problems with land management issues where the borders overlap an NPA region, as all NPA-related verbal and spatial data must be produced according to certain standards. Moreover, land management policies should be developed in relation to sustainable use and management of these areas. In line with this aim, the necessity for a protected area management system has emerged in which all spatial and verbal data are stored and can be used when needed. Before the creation of such a system, it is necessary to design a geographic information system (GIS)-based data model. This study examined the current situation of NPA site borders in a selected area using spatial data. It was revealed that the current system has no specific standards, the process is not being carried out systematically and the applied technical and legal criteria are not being properly followed. Therefore, the necessity has arisen for a data model design that contains all the necessary data in order to identify site boundary requirements. The data model design was generated using object-oriented Unified Modelling Language diagrams. Care was taken to ensure that the developed model was in compliance with the European Union-defined data standards (INSPIRE) and that it was implemented according to the environmental policy and standards set by the Land Administration Domain Model.

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7. On the errors-in-variables model with inequality constraints of dependent variables for geodetic transformation
W. Zeng, X. Fang, Y. Lin, X. Huang & Y. Yao

The Total least-squares (TLS) adjustment with inequality constraints has received increased attention in geodesy over the last three years. In the most recent work, inequality constraints have been presented that can restrict unknown parameters and independent variables, but no one has provided an inequality-constrained adjustment for restricting dependent variables. In this work, we review the TLS adjustment methods in terms of different model formulations and then investigate the errors-in-variables model with inequality constraints for dependent variables. Finally, we demonstrate the practicality of our approach with a planar geodetic transformation, where the uncertainty of the target observations is reduced via the inequality constraints for dependent variables.

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8. Analysis of ocean tide loading displacements by GPS kinematic precise point positioning: a case study at the China coastal site SHAO
H. Zhao, Q. Zhang, R. Tu & Z. Liu

Ocean tide loading (OTL) displacement amplitudes and phase lags of SHAO site are estimated by global positioning system (GPS), kinematic precise point positioning (PPP) and spectral analysis using 19 years of continuous GPS observations. In kinematic PPP, the 66 additional harmonic displacement parameters are replaced by the three time-varying displacement parameters without a priori modelled OTL displacements. By comparing the results with predictions from hybrid regional/global models, we are able to demonstrate that GPS/model agreements are at the level of 0.2 mm (horizontal) and 0.6 mm (vertical) for the four lunar constituents, 0.4 mm (horizontal) and 1.35 mm (vertical) for the four solar/sidereal constituents, and 0.2 mm (horizontal) and 0.3 mm (vertical) for the three long-period constituents. Finally, we conclude that GPS-derived lunar constituents can substitute for the model corrections in GPS data processing and the accuracy of GPS-derived solar/sidereal constituents needs to be improved by further studies.

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9. Impact of predicting real-time clock corrections during their outages on precise point positioning
Ahmed El-Mowafy

Real-time precise point positioning (RT-PPP) is a popular positioning method for natural hazard warning systems (NHWS) such as for monitoring tsunami and earthquakes. PPP relays on the use of precise orbits and clock corrections. Hence, the positioning accuracy of RT-PPP will significantly deteriorate when experiencing a discontinuity in receiving these corrections, for instance due to a temporary modem failure. The best available approach in this case would be to use the International Global Navigation Satellite Systems Service ultra-rapid (IGU) orbits and clocks that would result in a low positioning accuracy. In this paper, we present a simplified approach to a method that we recently proposed to bridge outages in the corrections and improve the RT-PPP accuracy compared with the use of IGU. In this method, the most recent IGU orbits are used as they are compatible with the RT orbits; however, the clock corrections are predicted as a time series using a linear model with four sinusoidal terms. The prediction errors resulting from this method, age of the model and its validity period are discussed. The impact of using the proposed approach is evaluated at a number of sites of known positions by comparing its performance to using IGU orbits and clocks. Moreover, the impact of using predicted corrections is assessed in different scenarios. The experimental results proved validity of the presented approach where positioning mean RMSE of less than 20 cm was maintained during the outage period.

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Survey Review 51, No 364. January/February 2019

1. Assessment of along-normal uncertainties for application to terrestrial laser scanning surveys of engineering structures
Tarvo Mill & Artu Ellmann

A method for estimating the range and spatial distribution of terrestrial laser scanning uncertainties occurring during the survey of engineering structures is presented and numerically verified. The emphasis is on the assessment of along-normal uncertainties of the surface to be surveyed. To investigate the behaviour of such uncertainties, various surveying scenarios are simulated and studied. Theoretical derivations are numerically verified, and these results are compared with those of previous empirical studies. The influence of along-normal noise on geometric modelling of surveyed surfaces is studied. In addition, suggestions are provided for how to optimising scanning locations, yielding the reduced ANU.

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2. Research into GNSS levelling using network RTK in Taiwan
Yi-Shan Li & Fang-Shii Ning

Modern height surveying obtains orthometric heights through geoid undulations and ellipsoidal heights derived from global navigation satellite system (GNSS), a process referred to as ‘GNSS levelling’. In this study, an efficient survey technology, the e-global navigation satellite system (e-GNSS), was used instead of static satellite surveying to execute GNSS levelling. The e-GNSS in Taiwan is based on Virtual Reference Station-Real-Time Kinematic technology and networks. The orthometric heights were calculated by subtracting the geoid undulations, derived from three geoid models (gravimetric, hybrid, and geometric models), from the ellipsoidal heights, derived from the e-GNSS. Additionally, two corrector methods, namely the difference and the corrector surface method, were adopted to improve the accuracies and the systematic errors. The experiment showed that the two corrector methods improved the accuracies of the orthometric heights in the gravimetric model by approximately 66.3 and 80.0% and mitigated the systematic errors in the gravity model by approximately 96.2 and 99.9%.

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3. On constrained integrated total Kalman filter for integrated direct geo-referencing
Vahid Mahboub, Mohammad Saadatseresht & Alireza A. Ardalan

A constrained integrated total Kalman filter algorithm is developed. It considers a quadratic constraint which may appear in some problems of integrated direct geo-referencing in particular when INS data is used as system equations of a Kalman filter algorithm. In such a case one encounters with a dynamic errors-in-variables (DEIV) model for system equations, although DEIV model has been already considered for equations of the Kalman filter algorithm and a solution namely integrated total Kalman filter (ITKF) has been given to it. Also this algorithm can be simplified to unconstraint case which is useful for some problems. It considers DEIV model for both observation equations and system equations of the Kalman filter algorithm. The predicted residuals for all variables including the random noise at the first epoch, the observational noise, the random system noise and the corresponding noise of two coefficient matrixes (in the system equations and the observation equations) besides the variance matrix of the unknown parameters are obtained. In two numerical examples, integrated direct geo-referencing problem is solved for a GPS-INS system.

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4. Optimisation of GNSS networks – considering baseline correlations
M. Amin Alizadeh-Khameneh, Lars E. Sjöberg & Anna B. O. Jensen

By considering global navigation satellite system (GNSS) observations, one can perform optimisation according to some pre-defined criteria and come up with the best location of receivers and optimum number of baselines. In practice, it is quite common to neglect the effect of correlations between baselines, and instead assume single-baseline-adjusted data in the optimisation procedure. However, in each session of observation, usually more than two receivers are simultaneously taking data from a number of common GNSS satellites, implying that the single- or double-difference observations are correlated. Our study designs an optimal observation plan for a GPS network in Skåne in southern Sweden, with the aim of determining possible displacements. Assuming three receivers in each session of observations leads to correlation between the GPS baselines, and consequently a fully populated weight matrix for each session of observation. A bi-objective optimisation model of precision and reliability is chosen to optimise the variance factor of each session, and eventually, design an observation plan. It is shown in this study that observing six out of ten possible sessions is sufficient to enable the network to detect a 5 mm displacement at each station. Assuming that the double-difference phase observations are uncorrelated changes the observation plan by retaining two more sessions. However, defining the weight matrix based on the double-difference observations requires the correlations to be taken into account, and neglecting them leads to incorrect results.

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5. Analysis of GPS satellite clock prediction performance with different update intervals and application to real-time PPP
H. Yang, C. Xu & Y. Gao

The GPS satellite clock offset prediction is investigated and applied to a real-time PPP system. First, the current situation of GPS satellite clock is introduced and analysed with respect to their stability. Then the satellite clock prediction with different update intervals is presented, in which the satellite clock day boundary jump is addressed. Afterwards, the investigation of the satellite clock prediction model for GPS satellite IIF clocks is carried out and the effects of periodic terms are discussed. After that, the verification of the satellite clock offset prediction will be carried out both in the time and positioning domain. Positioning accuracy at 0.021, 0.049, and 0.017 m in the east, north, and vertical directions can be obtained for 6-h static positioning using the predicted clock offset updating every hour, while the 3D RMS for kinematic real-time PPP is 0.360 m, with 28% improvement over that utilising the IGU predicted products.

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6. Non-contact detection algorithm and realisation of displacement of suspended cylinder
D. Xiao, L. Tan, Y. Su, B. Yu & Y. Yang

Large structures such as TV towers and suspension bridges often contain cylindrical components; the displacements of these suspended cylinders due to external agents are often of interest to ensure the integrity of the structure. This paper establishes an algorithm of the displacement monitoring for the suspended cylinder by non-contact surveying, which offers two main advantages over traditional contact-based methods. First, it does not require prisms to be physically mounted on the measuring target and second, the target consists of any three points on the same circle along the structure, which can be easily implemented. The algorithm is successfully applied in determining the displacement of suspended cylinder in high-rise structures such as a TV tower.

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7. Robust M-estimation using the equivalent weights constructed by removing the influence of an outlier on the residuals
H. Yu, Y. Shen, L. Yang & Y. Nie

The key issue in robust M-estimation is to construct the equivalent weights using the residuals of observations for down-weighting the outlying observations. However, the residuals of good observations are also possibly impacted by neighbouring outliers, thus directly down-weighting an observation according to its residual is not theoretically rigorous. Therefore, this paper focuses on the construction of equivalent weights for down-weighting the outlying and doubtful observations by removing the influence of the outlier on the correlated residuals. A down-weighting strategy using the corrected residuals to form the down-weighting factors is proposed. A simulated experiment and a practical experiment are respectively conducted to demonstrate the performances of the proposed down-weighting strategy compared to the direct down-weighting strategy (DDS) and recursive down-weighting strategy (RDS). The results show that the estimated performance of the proposed down-weighting strategy is comparable to that of RDS and the computation efficiency is obviously higher than that of RDS.

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8. DInSAR technique for slow-moving landslide monitoring based on slope units
Jiaxuan Huang, Mowen Xie, Asim Farooq & Edward J. Williams

Slow-moving landslides are one of the most widely distributed natural hazards in the world, with severe effects on the stability of structures. However, it is hard to be detected without monitoring method. In this paper, the Differential Interferometric Aperture Radar (DInSAR) technique is used to monitor the slow-moving landslides. But, the standardised procedures for the DInSAR technique are difficult to find the boundaries of landslides. The new segmentation method of slope units with the Digital Elevation Model is proposed. Moreover, the credible zone analysis is established based on slope units to filter the error value and improve the precision of monitoring results. Finally, according to the features of slow-moving landslides, the outcomes of DInSAR technique for slow-moving landslides inventory map are available. The methodology is tested at Wudongde valley area in the North-west China, where the SAR data and natural hazards inventory maps are available. The correctness of monitoring results will be verified.

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9. Calibration method of rotation and displacement systematic errors for ship-borne mobile surveying systems
Xiushan Lu, Chengkai Feng, Yue Ma, Fanlin Yang, Bo Shi & Dianpeng Su

Rotation and displacement errors between sensors and the Inertial Navigation System have significant effects on the accuracy of measured point clouds. In ship-borne mobile surveying systems, over and underwater targets are measured by a laser scanner and multibeam echo sounder, respectively. A simple calibration method and a universal calibration field are urgently needed to address both rotation errors and displacement problems for over and underwater sensors. First, a systematic error analytic function is established through the path that the geolocation expression of measured data is derived and substituted into the expression of known calibration planes. Then, the calibration expression that can calibrate both rotation errors and displacement is derived based on the least-squares criteria using a designed calibration pool. The calibrating results showed that for both over and underwater sensors, the accuracies of rotation errors and displacement estimation are better than 0.015° and 1.2 mm, respectively. After this calibration, the geolocation accuracy of measured points is better than 5 cm within a range of 30 m. The method can effectively calibrate systematic errors and serve as guidance to address the calibration problem for mobile surveying systems.

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10. Considerations on the land management system approach in Turkey by the experiences of a case study
Oktay Aksu & Muzaffer Can Iban

In Turkey, applications and activities for the use, acquisition and arrangements of land tenure rights are executed under the authorisation and responsibilities of a variety of public institutions in terms of concerned legislative framework. In this paper, a case study has been implemented for Istanbul not only to evaluate the quality and usability of existing data from different institutions but also to get conclusions and recommendations for future land management works. In the context of this sample work of preparing an inventory for land management and land use in 1:25 000 scale and related synthesis and pre-feasibility analyses; the inventory praxis for urban and rural areas have been undertaken separately. Layer overlay and synthesis of the data in the database are the essential parts of analysing and extracting the outputs supporting land management activities for the purpose of taking correct decisions. In that manner, an overview map of Istanbul's natural and settlement areas has been extracted.

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