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Email: Peter Collier


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Survey Review 50, No 360. May/June 2018

1. Reviewing the status of national spatial data infrastructures in Africa
Collins Mwange, Galcano Canny Mulaku & David N Siriba

The paper reviews the status of National Spatial Data Infrastructure (NSDI) in Africa, based on a survey conducted between April and October 2014. Web searches and data from the United Nations Department of Economic and Social Affairs E-Government survey of year 2014 were used to supplement the survey data. Using the SDI-Readiness methodology, the SDI-Readiness index is computed. Of the twelve countries reviewed, Senegal (0.69), Rwanda (0.65), South Africa (0.64) and Ghana (0.61) have higher indices; while Tanzania (0.33), Zimbabwe (0.33), Botswana (0.35) and Malawi (0.38) have lower indices. Countries with higher SDI-Readiness indices, which is a proxy for the capacity and willingness to develop an SDI, have a better chance of success in developing their NSDI. Lower indices implies that a lot more effort is required by the respective countries. Although all SDI components should be given equal prominence, the study suggests that more emphasis should be placed on improving the human and financial resources if Africa is to succeed in NSDI development.

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2. The concept of using the water cadastre databases components for the construction of multi-dimensional cadastre in Poland
M. Mika, M. Siejka, P. Leń & Ż. Król

The article has analytical and conceptual character. It contains a detailed analysis of the scope of cadastral information on waters based on actual data from the regional databases, which are established in four logistically major cities in Poland: Warsaw, Krakow, Wroclaw and Szczecin. The authors examine the contents of water cadastre databases in Poland and possibilities of using them in building the 3D cadastre. The concept of using water cadastre as a subsystem of the 3D cadastre presented in the work was carried out using graphical methods of the object-oriented analysis. The authors present a Real Estate Cadastre (REC) model based on synchronisation of the Land Register databases with the water cadastre databases carried out in District Water Management Boards. Modernisation and thematic expansion of Land Register databases, which act in Poland as cadastre, consistent with the presented REC model is a chance to improve the real estate market in Poland.

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3. From point cloud to BIM: an integrated workflow for documentation, research and modelling of architectural heritage
C. Rodríguez-Moreno, J. F. Reinoso-Gordo, E. Rivas-López, A. Gómez-Blanco, F. J. Ariza-López & I. Ariza-López

Heritage buildings traditionally have been tackled from several points of view: architectonic features, architectural style, archaeology, history, etc. Documents derived from those studies were classified and put together to form the documentation for consultation, taking decisions about its conservation, and restoration. Such a document organisation has some inconveniences: objects composing the building were treated as isolated objects not related to its adjacent objects. Nowadays technology may help to discover the relationship between architectural objects forming heritage buildings. The tool that makes it possible to include functionality in architectural objects is BIM (Building Information Modelling). In this paper the historical evolution of Saint Jeromés Church in Baza will be analysed and stored in a functional model which includes geometry and its current state. We propose a procedure for building the BIM through its historical roots and evolution to be included in each remarkable object modelled from the point cloud surveyed.

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4. Terrestrial laser scanner error quantification for the purpose of monitoring
Hasan Abdulhussein Jaafar, Xiaolin Meng & Andrew Sowter

In this paper, TLS error sources are discussed and the types and magnitudes of these errors are observed. Furthermore, a procedure for eliminating laser scanner outliers and reducing noise is introduced. For this purpose, two TLS instruments have been examined: Leica Scanstation P20 and P40. The results of the tests reveal the average noise level (mean errors) between two scans can be improved by using a surface model rather than direct point to point differencing, with improvements from 2.8 mm to 1.7 mm and from 0.7 mm to 0.2 mm for P20 and P40 respectively. In addition, the best fit local planes technique can remove outliers without reducing point density. Therefore, the maximum errors decreased from 50 mm (due to outliers) to 11 mm and from 13 mm (due to outliers) to 1 mm for P20 and P40 respectively.

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5. Triple-frequency GNSS models for PPP with float ambiguity estimation: performance comparison using GPS
M. Deo & A. El-Mowafy

This contribution proposes two new precise point positioning (PPP) models that use triple-frequency data, designed to accelerate convergence of carrier-phase float ambiguities. The first model uses a triple-frequency ionosphere-free linear combination that has minimum noise propagation and geometry-preserving properties. The second model uses a mixed code and carrier-phase linear combination with the same properties. A third model was also implemented, which uses individual uncombined triple-frequency measurements. The three models were validated using triple-frequency GPS data and their performance was compared to the traditional dual-frequency model in terms of the convergence time taken to achieve and maintain a uniform three-dimensional accuracy of 5 cm. Testing includes PPP processing of 1-h measurement blocks using 1–8 days of data from three locations in Australia. It was shown that all the three triple-frequency models had improved solution convergence time compared to the traditional PPP dual-frequency model although they gave almost similar accuracy and precision. The convergence time, when using the triple-frequency ionosphere-free model improved, by 10%, the improvement was 9% when using the mixed code-phase model, whereas the individual uncombined model resulted in 8% improvement.

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6. High performance filtering for big datasets from Airborne Laser Scanning with CUDA technology
Wioleta Błaszczak-Bąk, Artur Janowski & Piotr Srokosz

There are many studies on the problems of processing big datasets provided by Airborne Laser Scanning (ALS). The processing of point clouds is often executed in stages or on the fragments of the measurement set. Therefore, solutions that enable the processing of the entire cloud at the same time in a simple, fast, efficient way are the subject of many researches. In this paper, authors propose to use General-Purpose computation on Graphics Processing Units (GPGPUs) to process the big datasets obtained from ALS. GPGPU handles computation for computer graphics using GPUs (Graphic Processing Units). This study was based on programming model Compute Unified Device Architecture (CUDA), which facilitates the development of applications in GPUs. CUDA programming was used to carry out the filtration based on adaptive TIN model method in the initial stage of the processing of big ALS dataset. Results of the analysis showed that GPGPU can be used for the filtration of ALS point clouds and significantly speeds up calculations for big dataset.

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7. Terrestrial laser scanning for the monitoring of bridge load tests – two case studies
H. Lõhmus, A. Ellmann, S. Märdla & S. Idnurm

Terrestrial laser scanning (TLS) technology has various applications due to its capability of acquiring detailed 3D information about objects within a limited time-period. Yet, it is not widely used for the deformation monitoring of structures. To investigate the suitability of TLS for such tasks, a time-of-flight type Leica ScanStation C10 was used to determine the vertical deformations for two bridge load tests in Estonia, namely for the Loobu highway bridge and the Tartu railway overpass. The TLS results were verified with precise levelling, reflectorless tacheometry and dial gauges. Generally, deformation estimates obtained from TLS and other measurement techniques show sub-millimetre agreements (in terms of standard deviations). The maximum differences between the TLS and precise levelling results were 3.4 and 0.8 mm for the Loobu and the Tartu study, respectively. Since TLS has not yet reached the same accuracy as conventional geodetic high-precision techniques, it cannot fully replace them in high accuracy applications. However, TLS can be considered a complementary survey method for load tests as it provides valuable entire surface covering 3D information.

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8. Obituary: Clifford Dann MBE, FRICS
Dr Peter Collier

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Survey Review 50, No 359. March/April 2018

The following articles were presented at the Joint 2015 Malta FIG Commission 3 and Commission 7 Workshop

1. A comparison of address geocoding techniques – case study of the city of Zagreb, Croatia
V. Cetl, T. Kliment & T. Jogun

In the last years a lot of online geocoding services have become available online. Some of them are based on VGI as input data. Such services are very useful in the case of big amounts of objects that need to be geocoded. However, the quality of such services has still not been adequately explored. In this paper we tried to answer several questions regarding the quality of online geocoding services using the city of Zagreb in Croatia as a research area. The results of research showed that the currently available services need improvements to provide accurate sources for geocoding.

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2. Three-dimensional cadastre modelling of customary real property rights
D. Kitsakis, C. Apostolou & E. Dimopoulou

Although repealed from legislation, customary rights, restrictions and responsibilities (RRRs) deriving, inter alia, from religious, cultural and historical background still impact real estate property. Such RRRs may constitute complex, overlapping properties not easily accommodated within contemporary cadastral infrastructure. Peculiarities regarding customary law-derived properties’ geometry and contradictions to statutory legislation result in difficulties integrating them to national cadastral systems. This paper investigates the status of customary law-derived RRRs, presenting a three-dimensional modelling and recording application for the Hellenic Cadastre, adjusting Land Administration Domain Model, examined through implementation on two cases of special real property objects in Greece.

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3. A new model for cadastral surveying using crowdsourcing
K. Apostolopoulos, M. Geli, P. Petrelli, C. Potsiou & C. Ioannidis

A ‘fit-for-purpose’ approach is developed, tested and presented for cadastral surveys through increased owners’ participation using new technology and m-government services. Three case studies are reported, for urban, suburban and rural areas, with a combined use of two mobile applications: a commercial software package (ESRI’s Collector for ArcGIS) and an opensource self-developed application named BoundGeometry. The parameters of time, quality and accuracy are assessed and the identified difficulties are classified. It is concluded that the method is applicable both in developed and developing countries, and each time adjustable to the available infrastructure.

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4. 3D visibility analysis indicating quantitative and qualitative aspects of the visible space
D. Golub, Y. Doytsher & D. Fisher-Gewirtzman

This paper presents the development of a 3D visibility analysis model that consist a combination of objective calculations and a subjective evaluation, representing the value of the view and its possible impact on the perception of a viewer. The model, developed in Matlab, has default weightings for different elements of the view, which can be changed in accordance to future users. A bounding box, defined as working area consisting buildings and topography, is divided into equal-size voxels and sub-voxels for higher accuracy. This model may be further developed for use in practice to support a sustainable future urban environment.

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Regular contributions to the journal

5. Bridge pier settlement prediction in high-speed railway via autoregressive model based on robust weighted total least-squares
X. Gong & Z. Li

The autoregressive model for time series prediction is a common method in settlement prediction. In the traditional parameter estimation of autoregressive model, least-squares (LS) is the method, which only considers the errors in the observation vector. However, the errors in the coefficient matrix have not been considered. To solve this issue, weighted total least-squares (WTLS) method is developed for parameter estimation. However, it does not consider the possible gross errors in observations, which may lead to a reduction in the robustness and reliability of parameter estimation. In order to solve this problem, in this study, robust WTLS (RWTLS) method is proposed to estimate parameters of autoregressive model for bridge pier settlement prediction in high-speed railway. A comparison with LS, robust LS (RLS) and WTLS methods is conducted for bridge pier settlement prediction and two sets of observed data are used in this evaluation. The results of experiments show that the variance components and the mean absolute values of predictive residuals obtained by WTLS and RWTLS methods are smaller than those by using LS and RLS methods in the case of modelling data without gross errors, and the variance component and the mean absolute value of predictive residuals obtained by RWTLS method is the smallest in the case of modelling data with gross errors. It shows that autoregressive model settlement prediction for bridge pier by using RWTLS method is more reliable and accurate than LS, RLS and WTLS methods in high-speed railway.

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6. Kriging and moving window kriging on a sphere in geometric (GNSS/levelling) geoid modelling
M. Ligas & M. Kulczycki

A comparison of kriging and moving window kriging (MWK) on a sphere is performed on GNSS/levelling data. The study was to give the answer on whether there is a significant gain in prediction accuracy when we apply an MWK instead of ‘classical’ kriging and also to what extent the use of global geopotential model EGM2008 improves prediction. The quality of prediction for all kriging and data variants has been investigated on three regions (being on the territory of the conterminous USA) characterised with a different spatial extent and density of sampling. Numerical tests revealed that in case of high-sampling density there was no accuracy gain when using MWK instead of classical kriging (cK). In contrast, for less numerous datasets and a much larger spatial extent (low-sampling density) MWK adapts itself to data much better than cK. Incorporation of EGM2008-based undulations as a long-wavelength trend for both cases (classical and moving window) significantly improved prediction quality.

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7. Chronology of the development of geodetic reference networks in Serbia
Oleg Odalović, Miljana Todorović Drakul, Sanja Grekulović, Jovan Popović & Danilo Joksimović

In this paper, the development of geodetic reference networks in Serbia is shown. This historical summary covers the time from the first organised work in 1855 until today. Special attention has been paid to the establishment of the modern network using Global Navigation Satellite Systems (GNSS). Within the networks established by GNSS, two last realised networks are especially distinguished. The first one is a classic spatial reference network SREF (Serbian Reference Frame) established in 2003, and the second one is a permanent stations network – AGROS (Active Geodetic Reference Network of Serbia) realised in 2006.

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8. Study on high-precision regional monitoring method of high-grade highways subsidence under the influence of underground mining
B. C. Zhao, H. Z. Li, G. L. Guo & L. Q. Mi

High-grade highways are the foundation of regional economic development. How to monitor the deformation of high-grade highways under the influence of underground mining and guarantee their safe operation is very important and is directly relevant to regional economic development. Considering that Differential interferometric synthetic aperture radar (D-InSAR) technology has low monitoring accuracy around the maximum subsidence and high-accuracy levelling can only monitor the deformation of finite number points, the method of assimilating the D-InSAR data and levelling monitoring data based on Kalman filtering theory is proposed to improve precision of regional monitoring. Research results indicate that data assimilation results based on ensemble Kalman filter are much better than the inversion results and D-InSAR data. When applied to Zouji Highway of Jining, the total RMS is 17.7 mm after assimilating the D-InSAR data and levelling monitoring data, which can meet accuracy requirements of deformation monitoring of high-grade highways. Research results are of theoretical and practical significance to guarantee safe operation of high-grade highways under the influence of mining activities.

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9. On the total least-squares estimation for autoregressive model
W. Zeng, X. Fang, Y. Lin, X. Huang & Y. Zhou

The classical Least-Squares (LS) adjustment has been widely used in processing and analysing observations from Global Satellite Navigation System (GNSS). However, in detecting temporal correlations of GNSS observations, which can be described by means of autoregressive (AR) process, the LS method may not provide reliable estimates of process coefficients, since the Yule-Walker (YW) equations refer to structured Errors-In-Variables (EIV) equations. In this contribution, we proposed a Total Least-Squares (TLS) solution with the singular cofactor matrix to solve the YW equations. The proposed TLS solution is obtained based on the fact that random errors belong to column space of its cofactor matrix. In addition the proposed solution does not need any substitution of the squared true parameter vector as done by the current publications. Finally, we simulate the AR process to prove that our solution is more reliable than the existing methods.

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Survey Review 50, No 358. January/February 2018

1. A new approach to calculate the land fragmentation indicators taking into account the adjacent plots
J. Janus, M. Mika, P. Leń, M. Siejka & J. Taszakowski

Land fragmentation is a phenomenon which constitutes one of the biggest obstacles to profitable agricultural production. Measurable estimation of this phenomenon is possible by a number of known indicators, based on the surface area of parcels in the given area, their location in space and belonging to individual farms. This method of calculation of the indicators is inaccurate due to the phenomenon of neighbourhood of plots which belong to the same owners. For the purposes of calculating the ratios of actual fragmentation of land, these parcels should be treated as one complex. The article presents a proposal for the adjustment of existing methods of determination of the fragmentation of land indicators, taking into account these phenomena. The object of the research covered area of the voivodeship of Malopolska located in the southern part of Poland. Developed by the authors, method of calculation of land fragmentation indicators, based on complexes of land belonging to the same owners (complexes of plots aggregation), gives very good results in the evaluation of the intensity of the land fragmentation. Obtained in this way, indicator’s land fragmentation represents the real situation on the ground.

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2. Surface area calculation for DEM-based terrain model
S. Xue, Y. Dang, J. Liu, J. Mi, C. Dong, Y. Cheng, X. Wang & J. Wan

The surface area calculation is meaningful for a variety of space-filling phenomena, for example the packing of plants or animals within an area of land. An integral method for calculating the landscape surface area is proposed by considering the curvature of terrain and the measurement errors in Digital Elevation Model (DEM) data. Applying the least squares method, with the DEM data we estimate the first-order and second-order derivatives of the terrain surface to reduce the influence from the DEM data errors. It shows that the first-order derivatives estimated are statistically independent to the second-order derivatives estimated when using a symmetrical configuration composed of a series of DEM points. The surface area within a polygonal region is obtained by partitioning the polygonal region into a series of squares, rectangles and triangles. The proposed method is compared with the triangle-based methods and the results show that the proposed method is more robust.

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3. Informal economies, state finances and surveyors
P. van der Molen

All countries host informal economies, sometimes even exceeding the size of the formal economy. Living in the informal economy means for citizens that they and their activities are invisible for the government. Governments miss information about which people live in their country and what economically happens. They miss relevant data to develop policies, to monitor implementation and to levy taxes for generating budget. This hampers good governance and state building. This paper analyses the problem, and argues that when surveyors would expand their capacity for administration of land to other recordable subjects and objects, they can contribute to a solution.

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4. Height biases of SRTM DEM related to EGM96: from a global perspective to regional practice
A. Üstün, R. A. Abbak & E. Zeray Öztürk

It is investigated to what extent EGM96 affects the accuracy of digital elevation model (DEM) produced from the shuttle radar topography mission (SRTM). Global and regional analysis of EGM96 compared with EGM2008 indicate that locally there are large differences distorting to the accuracy level of SRTM DEM. In the absolute sense, the overall geoid differences throughout 1x1 arc-degree tiles reach −5 m in the northeast and 2–3 m in the southern parts of Turkey. A numerical investigation over the test profiles of 200–700 km length running at various directions proves that a possible vertical datum change from EGM96 to EGM2008 yields systematically more accurate height information with an improvement of up to 2.5 m. A GPS-levelling traverse of about 900 km length points out some key patterns of this recovery. Consequently, a correction for the present version of SRTM DEM should be considered in critical implementations of Earth sciences like geoid or water flow modelling, especially for areas where EGM96 shows weak performance.

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5. Maintenance of the state survey in the Republic of Montenegro
R. Đurović, I. R. Aleksić & R. Mihajlović

The paper provides an overview of the maintenance of the state survey, as the foundation for the development of the geodetic infrastructure, real estate cadastre, mapping and the National Spatial Data Infrastructure (NSDI) in the Republic of Montenegro. A proper understanding of the problems that emerge in the maintenance of the real estate cadastre requires familiarity with its background, i.e. the conditions under which it emerged. Particular attention is focused on geodetic reference networks, as the foundation upon which the cadastral databases were established and have subsequently been maintained, with analysis of their occurrence and current state included.

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6. The use of low-cost, single-frequency GNSS receivers in mapping surveys
M. Tsakiri, A. Sioulis & G. Piniotis

The emergence of low-cost, navigation-type receivers capable to provide carrier-phase data (the so-called high-sensitivity carrier-phase positioning) has been steadily growing over the recent years. The aim of this study was to evaluate the positioning performance of a high-sensitivity receiver in a network real-time kinematic environment for mapping surveying applications. Specifically, using as rover receiver the u-blox NEO-7P module and the low-cost antenna Tallysman TW2410, sets of data were collected for the purpose of mapping surveying. The external accuracy of the obtained solutions is considered using different positioning techniques and the internal indicators of the system during real-time kinematic (RTK) positioning are assessed. The assessment indicates that in benign environments this type of receivers produce results that are comparable to RTK positioning using geodetic receivers and with a significantly lower cost.

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7. An effective QR-based reduction algorithm for the fast estimation of GNSS high-dimensional ambiguity resolution
L. Lu, W. Liu & X. Zhang

To fast estimate high-dimensional ambiguities, we propose a new lattice reduction algorithm based on QR decomposition, which achieves fast integer transformation through an iterative strategy of whole size reduction and the deep insertion of minimum basis vectors. It acquires better basis vectors for ambiguity resolution. The feasibility of the proposed algorithm is verified by comparing its performance with those of LAMBDA, LLL, the parallel Cholesky-based reduction algorithm with ascending sorting (ASCE), and a modified LLL algorithm with deep insertions (PotLLL) under three experimental scenarios. The Hermite defect and defined length ratio are used to measure the reduction quality. Both metrics verify that our proposed method acquires a good reduced basis for accelerating the ambiguity search. To evaluate the practical ambiguity resolution behaviour, we tracked the runtime of ambiguity resolution. The results show that the computational efficiency of the proposed algorithm is better than those of the comparative algorithms.

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8. Representation of the rotation parameter estimation errors in the Helmert transformation model
Q. Wang, G. Chang, T. Xu & Y. Zou

In the Helmert transformation model, the rotation is more difficult to be treated in terms of representation, estimation, and error analysis. First, two classes of representations of the rotation, i.e. the redundant class including the direction cosine matrix and the unit quaternion, and the minimum class including the rotation vector, the Gibbs vector, the modified Rodrigues parameters, and the Euler angles, are reviewed. It is concluded that in general the redundant class should be preferred as they are transcendental-function-free, singularity-free, and discontinuity-free. Second, two classes of estimation errors, i.e. the additive and the multiplicative errors, are defined and compared in detail. While the multiplicative errors are more convenient, the relationship among different representations and the relationship with their additive counterparts are also explored from first principle. It can be seen as a review paper; however, the content concerning the relationship between the additive and the multiplicative errors is believed new.

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9. Introduction to multiple regression equations in datum transformations and their reversibility
A. C. Ruffhead

This paper provides an introduction to multiple regression equations as a method of performing geodetic datum transformations. The formulae are particularly useful when there are non-linear distortions that need to be built into the transformation model. However, the equations take the form of a one-way transformation, usually a local geodetic datum to a global datum. The standard procedure for applying the equations to obtain the reverse transformation only gives approximate results relative to the original model. This paper quantifies the problem and describes three methods for computing the reverse transformation (or inverse transformation) more accurately.

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10. Comment on ‘The use of laser scanning as a method for measuring stairways following an accident’
R. Bowman, M. Roys & N. Davies

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11. Obituary: George Russell ‘Brim’ Brimacombe 5 June 1939–27 July 2017
Dr Peter Collier

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