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Survey Review 44, No 327. October 2012

1. A novel Stop&Go GPS precise point positioning (PPP) method and its application in geophysical exploration and prospecting
Zhang, X H; Guo, F; Li, X X

A new method of Stop&Go positioning method based on PPP is proposed in this paper with an application to geophysical exploration and prospecting. The method couples the kinematic PPP and static PPP, where the continuous kinematic observations between two sequential short static observations provide a correction for the carrier phase ambiguities. Therefore, the whole consecutive observations, including both static and kinematic segments, will contribute to the ambiguities convergence of each point with few epochs' static observation. The experimental results showed that for the measured points which are observed over 60 s with 5 s sampling rate in static mode, the positioning accuracy can reach 5–6 cm in the horizontal and 0.1 m in the vertical; for those points which are observed over 10 s with 5 s sampling rate in static mode, the positioning accuracy is about 8–9 cm in horizontal and 0.12 m in vertical.

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2. Analysis and filtering of the effect of tides on the hydrostatic levelling systems at CERN
Boerez, J; Hinderer, J; Jones, M A; Rivera, L

To meet alignment tolerances that are becoming tighter and tighter (±10 μm for the Compact Linear Collider (CLIC) project), the surveyors in the Survey Section at European Organization for Nuclear Research (CERN) must master the tilt effects exerted on their hydrostatic levelling system (HLS) networks. These effects are many and have varied consequences, although the majority of them tilt the ground and also the water surface present inside HLS (sensors in a homogeneous way. In order to model all inclinations together as a block, we have adjusted, at each time t, the line through the seven sensors in the Transfer Tunnel 1 (TT1) experiment. After removal of this signal, the residual amplitudes of the readings are less than the HLS alignment tolerances of the proposed CLIC main accelerator. In addition, the residual signals have lost their semidiurnal and diurnal periodic components, proving that any local effects in the TT1 facility cannot be detected with the accuracy of our systems. Further progress has to be made however, to master the effect of temperature on the HLS. The periods remaining in the residual HLS signal proves the presence of uncorrected thermal effects.

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3. An approach to reliable rapid static GNSS surveying
Bakula, M

This paper presents a methodology for reliable surveying and processing of GNSS observations in a rapid static survey conducted in open terrain as well as with the limited availability of satellites. The surveying and data processing technology presented allows reliable determination of coordinates under difficult observation conditions, e.g. in a forest with significant obstacles to satellite signal reception. The test GNSS surveys were conducted in two points with full availability of satellites and a point with a high intensity of obstructions. The test point coordinates were determined by three GNSS receivers positioned simultaneously in line on a special base at a distance of 0·5 m from one another. Given the possible gross errors of the determined baseline coordinates, the simultaneous application of three GPS/GLONASS receivers for a single point allows reliable determination of coordinates even in locations with severe obstructions. Test surveys were conducted using Topcon Hyper Pro receivers and the ASG-EUPOS system network of reference stations. The presented survey and data processing methodology allows users to obtain reliable coordinates with accuracies expressed in centimetres during a rapid static survey session of a few minutes or even just one minute.

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4. The establishment of a new gravity reference frame for Serbia
Odalović, O; Starcević, M; Grekulović, S; Burazer, M; Aleksić, I

In this paper, gravimetric work performed in the territory of Serbia is shown chronologically from the end of the nineteenth century until present. The first work, which was based on data from pendulums, is presented briefly. Details are provided on the establishment of the first order gravimetric network from 1952 and a basic gravimetric network created 10 years later. A review of a detailed gravimetric measurement, performed simultaneously with these works for establishing the networks, is also given. Special attention is dedicated to the first measurements using absolute gravimeters that were performed in 2007, but also to establishing a new basic gravimetric network as a basis for a future detailed gravimetric survey. From all of the shown data, it is to be noted that ex-Yugoslavia and then Serbia followed to a great extent modern trends of gravimetric network development. Unfortunately, the network maintenance was inadequate, and a database was not established due to the political and economic changes in the society, which caused suspension of some institutions that were authorised for these types of jobs.

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5. Effect of Δ on xyz coordinates
Rollins, C M; Meyer, T H

It is well known that the reference ellipsoid of the World Geodetic System 1984 (WGS 84) has the same semi-major axis length as that of the reference ellipsoid of the Geodetic Reference System 1980 (GRS 80) but that they differ in flattening values by 1·643×10−11. It is also well known that this minute difference is of no practical consequence in the change that it imparts to geodetic coordinates determined with the different reference ellipsoids, but no formal bounds appear to have been published. This short note presents an analysis that gives bounds on the coordinate changes, which are shown to depend on geodetic latitude but on neither ellipsoid height nor longitude. The analysis has relevance to geodetic-coordinate transformations between reference frames employing different reference ellipsoids; it supports the National Geospatial-Intelligence Agency’s decision to continue to use the WGS 84 reference ellipsoid in upcoming realisations of the WGS 84 datum.

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6. Anomalous atmospheric refraction and comments on ‘fast and accurate determination of astronomical coordinates …’ (Balodimos et al. , 2003. Survey Review , 37(290): 269-275)
Hirt, C

Balodimos et al. (2003, Survey Review, 37(290): 269-275) presented astrogeodetic instrumentation for the determination of astronomical coordinates, and stated an accuracy of ±0·01″ would be achieved within few hours observation time. However, these authors did not address anomalous atmospheric refraction, the effect of which is relevant for any accurate determination of astronomical latitude Φ and longitude Λ. This correspondence briefly reviews anomalous refraction and its effect on astrogeodetic methods, by first defining anomalous refraction, describing its origins, summarising results of theoretical and empirical studies, and giving ways to mitigate its effect. This demonstrates that anomalous refraction represents a major obstacle for determining astronomical coordinates (Φ,Λ) at the 0·01″ accuracy level from just a few hours of star observations, as claimed by Balodimos et al. (2003).

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7. A case study of geo-ICT for e-government in Nigeria: does computerisation reduce corruption in the provision of land administration services?
Akingbade, A O; Navarra, D D; Georgiadou, Y; Zevenbergen, J A

This paper examines the role of the Abuja geographic information systems as an e-government policy initiative for promoting the reduction in corruption in the provision of e-land administration services and good governance in general. The paper explores the contribution of e-land administration with regard to the different forms of corruption (i.e. fraud, forgery, multiple applications, bribery, nepotism and favouritism, and white collar malpractice) as well as the different services (i.e. legal searches, recertification of titles, granting rights of occupancy, consent to alienate and regularisation of titles). Generally, our findings suggest that corruption was reduced with the introduction of electronic services for the verification of land records through legal searches and the recertification of land titles. Yet, other forms of corruption, such as nepotism and favouritism, are persistent and increasing.

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8. A change based framework for theory building in land tenure information systems
Barry, M; Roux, L

The paper presents a framework for categorising and assessing theories in land tenure information systems (LTIS) to improve coherence and critical rigour in LTIS theory development. The LTIS research area is dominated by the land titling theory which holds that land titles provide tenure security, which therefore may serve as collateral for credit and thus stimulate economic activity. However, this hypothesis is not valid in many instances. Alternatives to the land title theory are isolated due to the predominance of case study research in the area, the small number of researchers focused on LTIS as a research area and the difficulty in testing these alternative theories with empirical evidence, because many of them are not expressed in a form that renders them suitable for testing. In the framework, theories are examined according to the context of the situations an LTIS is meant to serve, within which the most significant variable is the level of change or uncertainty. A taxonomy of theory presented in library information science is adapted to assess the level at which a theory may be generalised in a particular context type and linked to the framework. One way of estimating a theory’s level of general applicability is the number of times it has been validated empirically in different contexts. The framework should serve as a visualisation and analytical tool to stimulate the development of a more rigorous theoretical foundation for these information systems. The present paper is of primary interest to land administration and land information researchers, but it also has important implications for practitioners.

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9. Extended S-transformation as a tool for deformation analysis
Even-Tzur, G

In geodetic monitoring networks, the deformation parameters can be estimated only if the datum of the network has not been changed between measurement epochs. The measurements of a monitoring network must be adjusted so that the datum remains undisturbed. In deformation analysis, similarity transformation is used intensively in order to bring all monitoring campaigns to the same common datum. However, there are geodetic measurements which contain datum definition components. When part of the datum definition contained in the measurements is not constant in time, the estimated deformation parameters could be erroneous. An appropriate approach should be taken to prevent the inclusion of these components in the adjustment of a 4D network. If not, the result is an inevitable mixture between the deformation parameters and the datum components of the measurements. The extended S-transformation allows us to strip the datum content from a set of coordinates that contain the complete contribution of the geodetic measurements to a datumless set of coordinates. Based on the datumless sets of coordinates, the variations in the network geometry can be modelled by means of a physical model without the influence of a datum definition inherent in geodetic measurements. Following a short introduction of the concept of extended free net adjustment constraints, the development of an extended S-transformation is presented. Two examples of a trilateration network and a GPS network are presented for implementing the method.

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Survey Review 44, No 326. July 2012

1. Michael Alan Ralph Cooper (1935-2012) Obituary and Tribute

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2. Using digital close-range photogrammetry as a QA/QC tool in construction: practical cases
Abdel-Bary Ebrahim, M

In the construction field, the terms quality assurance and quality control (QA/QC) have an important purpose, which is to provide the final product with the required quality. Some tools must be applied to ensure and control the quality of construction testing and measuring are important examples of such tools. Sometimes they require accurate measurements depending on the issue at hand. Close-range photogrammetry is one of the most important and accurate measuring techniques that does not require direct contact with an object. Additionally, most of the procedure for close-range photogrammetry can be carried out in the office. The objective of this paper is to present the use of close-range photogrammetry as a useful and accurate measuring tool for QA/QC in the construction field. We have applied close-range photogrammetry to two practical cases in a construction site to demonstrate its application to the issues of quality assurance and quality control.

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3. From parcels to global cadastre: challenges and issues of the post-cadastral reform in Quebec
Roy, F; Genovese, E

In 1985, the Government of Quebec decided to update its cadastre by producing an accurate computer based representation of private land division in the province. The cadastral reform project is unique in terms of scale, methodology and final product characteristics. The end result of the cadastral reform will be a system no longer based on single parcel paper maps, but a global digital map. Despite the strict framework within which the Quebec cadastral reform was launched in 1992, this renovation has raised unexpected questions that still need to be answered. The aim of our study is to describe the challenges and problems that have been generated by this transition. First of all, the impacts of the new cadastral system on land surveyors’ professional activities have neither been fully identified nor estimated. In the past, the idea of integration into a large cadastral grid was not compulsory and land surveyors used to represent their cadastral operations on parcel plans without showing the neighbouring properties. Therefore, these plans often contained inaccuracies that were non-apparent until one tried to integrate the individual lots and then created into a global map. Discrepancies between neighbouring lots could occur at this occasion, forcing the land surveyor to make a deeper investigation of the area. The main challenge will be to ensure the improvement of the global cadastral map, by enhancing its consistency in accordance with field survey data, and by implementing correction procedures, particularly when scale or projection changes are required.

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4. Real-time deformation measurements using time series of GPS coordinates processed by Kalman filter with shaping filter
Li, L; Kuhlmann, H

Global positioning system (GPS) has been widely used for real-time deformation monitoring. The Kalman filter is one of the optimal methods to process time series of GPS coordinates for a deformation analysis in real-time, but it requires white noise. However, the time series of GPS coordinates obtained from a GPS receiver with a high sampling rate contain coloured noise. A shaping filter can be used to model the long-term movement of coloured noise based on the estimation of the stochastic model of the time series of GPS height coordinates. Thus, a Kalman filter with a shaping filter is proposed to process the different types of deformation time series of GPS height components in real-time. The results show that not only the time series of stepwise deformations but also the time series of continuous deformations can be processed by the Kalman filter with a shaping filter. The coloured noise can be extracted from the GPS time series and the accuracy of the processed coordinate time series has been improved.

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5. Deformation detection for ISKANDARnet
Lim, M C; Setan, H; Othman, R; Chong, A K

Tragedies and disasters in the past have shown the threats that are associated with large construction projects. A timely identification of precursory movements may save lives and minimise collateral damage. An advanced global positioning system (GPS) continuously operating reference station network known as ISKANDARnet is operated continuously to detect deformations in Iskandar, State of Johor, Malaysia. In this study, three GPS continuously operating reference stations from the ISKANDARnet were used as the object stations along four nearby international GNSS service stations (NTUS, XMIS, COCO and PIMO) used as reference stations. The GPS data were streamed and processed by a GPS processing software module, Bernese processing engine. A deformation analysis module was developed using the MATLAB programming language to carry out continuous two-epoch analyses. The development also involves the implementation of the iteratively weighted similarity transformation method and a final S-transformation to analyse the GPS data. By applying these techniques, unstable object points were identified within the monitoring network and accurate displacement vectors were computed. The time-based variation of the displacements was shown in this paper. Test results showed that the system performed satisfactorily.

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6. A new fusion scheme for accuracy enhancement and error modification in GPS/INS tight integrated navigation
Wu, F-M; Yang, Y-X; Zhang, L-P

In tight integrated navigation based on pseudoranges and Doppler observations, the positioning precision is poor and the modification of the attitude angles are not accurate for poor precision of pseudorange observations. The outliers and the dynamic errors can easily influence the precision of adaptive filtering, because the number of measurements is usually less than that of the state parameters. Therefore, a new fusion scheme of two-step adaptive robust filtering based on the observability of the parameters is presented for accuracy enhancement and error modification. First of all, the process of the adaptive Kalman filtering of tight integration based on the predicted residuals is given and the limitation is analysed. Then, the formulas and the new fusion algorithms are deduced and analysed. In the first-step filtering of the new algorithms, an adaptive factor is used to control the influence of the dynamic errors and modify the attitude errors. In the second-step filtering, robust equivalent weight is adopted to resist the bad influence of the outliers. Finally, an actual calculation is given. First, the results show that precise random models and direct estimates can give correct modification, while poor direct estimates will lead to incorrect modification. Second, they also show that the new fusion scheme can control the disturbances of the state and the outliers of the observations compared with the adaptive Kalman filtering of tight integration based on the predicted residuals. And the navigation precision does not decrease, while the integration period becomes longer and the INS noise become higher. The INS errors can be accurately estimated and the precision of attitude angles is improved.

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7. Sea levels around Barbados from tide gauges and satellite altimetry
Miller, K; Hart, B; Sydney, P

Like many of the small island states of the Caribbean, mean sea level on Barbados was initially established using a short term data set, and this served the purpose of marine navigation. In the 70 years since sea levels were first observed, a number of other measurement series have been made for different purposes. Sea level is now a concern for coastal vulnerability. Data that have been acquired over the years is now brought together with some recent observations to investigate the trend. Discrepancies in the datum that have been used are identified, and further work is undertaken to investigate the cause of variations in sea level that are seen to occur beyond normal tidal and meteorological influence. Satellite altimetry is used with recently acquired data from a tide gauge to show that eddies formed in the Atlantic Ocean can change sea levels around Barbados by up to 0·3 m. Comparative results obtained using tide gauge data and satellite altimetry confirm mean sea level and seasonal variation. Results suggest that integration of these techniques is ideally suited to determining variations in sea level around small island states.

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8. Contemporary surveying education changing with the times
Young, G O; Smith, M J; Murphy, R

The role of the surveyor remains relevant to the modern world, but there are notable changes in how surveyors carry out their work and in the nature of that work. This paper argues that such changes in the professional arena demand changes in the associated educational programmes. The discussions are primarily based on findings from a study of a wide cross-section of university-based surveying courses from diverse countries. Issues of curriculum and pedagogy and the relationship between education and the surveying industry are explored. As it relates to curriculum, contemporary surveying education is viewed vis-à-vis educational models. The comparison is conducted at two levels: in relation to content delivery strategies and in relation to their philosophical bases. Other issues considered to be relevant to contemporary surveying education are discussed. These include shifts in how surveying is perceived in industry and in academia, pedagogical approaches employed in surveying courses and the relevance of theories of learning to pedagogical and curricular development. This paper ends with a discussion on the nature of the relationship between university-based surveying education and the wider world of professional surveying practice.

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9. Some remarks on GNSS integer ambiguity validation methods
Li, T; Wang, J

Ambiguity resolution is an indispensable step in fast and high precision Global Navigation Satellite System (GNSS) based positioning. In general, ambiguity resolution consists of three steps. The first step is to estimate the ambiguities using a least-squares estimation process, from which the so called ‘float solution’ or real valued solution is obtained. Then in the second step, the float solution is used to search for the integer ambiguities. Once integer ambiguities are resolved, the last step is to apply the integer ambiguities into the models so that fairly accurate fixed solution can be generated. Owing to the importance of the integer ambiguities, one indispensable procedure that needs to be implemented in the second step is integer ambiguity validation. Over the past decades, considerable work has been concentrated on this procedure and various approaches have been proposed, such as R-ratio test, F-ratio test, W-ratio test, integer aperture estimator, etc. However, their performances are controversial. Therefore, in this contribution, an overview of the existing ambiguity validation methods is firstly presented, and then some numerical analysis is carried out to evaluate their performances.

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10. Analysis of short and discontinuous tidal data: a case study from the Aegean Sea
Pytharouli, S I; Stiros, S C

An algorithm, which permits to compute the statistically significant tidal constituents and amplitude, duration and frequency of recurrence of meteorological surges, in the case of short, discontinuous or noisy tidal records, is presented. This algorithm is based on step by step filtering techniques and least squares based spectral analysis in both the frequency and time domain, and hence, it permits to avoid, first, the noise introduced in measurements as a result of interpolations, zero padding or fragmentation, and second, large uncertainties introduced by automated tidal computation routines, mainly designed for high tidal amplitudes and high signal to noise ratio data. Additionally, it is simple to follow by non-specialists in oceanic processes. The efficiency of the proposed algorithm is demonstrated on the basis of comparison of annual and interannual, high accuracy and conventional tidal records from the Aegean. This region is characterised by an astronomical tide of the order of 10 cm, about one order of magnitude smaller than the meteorological tide, and hence represents an extreme tidal environment, with very low-signal-to noise ratio values. Such data permit to evaluate the adequacy of an algorithm to successfully analyse records of short duration or with significant gaps, cases in which conventional algorithms fail. The proposed algorithm is therefore suitable for the analysis of recent, high sampling frequency but short duration records, many of which are available online, and for the identification of small amplitude tectonic, oceanographic signals, useful for climatological studies, satellite altimetry calibration or even to test malfunction of instruments.

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Survey Review 44, No 325. April 2012


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1. Use of airborne laser scanning to characterise land degradation processes – the Dead Sea as a case study
S. Filin, A. Baruch, S. Morik, Y. Avni and S. Marco

Evaluation of surface processes requires efficient means to quantify their effect. Despite the span and three-dimensionality of these processes, they are usually monitored using land surveying or naive 2D image interpretation. Therefore, the results are partial in terms of coverage and detail, and are mostly qualitative. We study in this paper the application of high resolution airborne laser scanning data for detection and characterisation of geomorphic processes. The Dead Sea region, where lake level drop of .1 m/year has led to dramatic change in the surrounding geomorphic system, and is endangering the natural environment and infrastructure, is used here as our case study. We propose a feature extraction methodology which responds to the measurement noise and surface texture and show how laser data are optimal for detecting such phenomena, accurately characterising them and providing quantitative data, which are all necessary to understand their development.

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2. Geometric quality enhancement of legacy graphical cadastral datasets through thin plate splines transformation
D N Siriba; S Dalyot; M Sester

In some parts of the world, mainly developing countries, analogue graphical cadastral datasets are still being used, despite the fact that they usually contain large and differential positional distortions. This is because not only do they contain useful information, their replacement would involve lengthy legal procedures, huge financial costs and technical challenges as well. This paper presents a novel approach for the conflation of such legacy graphical cadastral datasets to more reliable and accurate topographical datasets based on the matching of linear features via a non-rigid transformation using thin plate spline transformation. The approach consists of three key steps: extraction of road network which is potentially contained in the graphical cadastral maps; matching of corresponding point and linear features between the extracted road network and a more reliable road network dataset; and computation of the non-rigid transformation between the datasets. Applying this reliable and accurate transformation quantification to the original legacy graphical cadastral dataset showed significant improvement in its geometric quality and positional accuracy.

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3. Genetic Algorithms: a stochastic approach for improving the current cadastre accuracies
Shnaidman, A; Shoshani, U; Doytsher, Y

The necessity for an analytical cadastre is impelled by the reality of the modern world. Over the past few decades or so, the issue of land management, including cadastral databases and information systems, has become increasingly acute. Even though, many countries still continue to rely upon a graphical, not homogeneous and inaccurate cadastre. This situation is far from ideal and is unsuitable for an efficient handling of land properties and real estate management. Much research has been done to improve the existing system; however, most currently employed techniques to achieve a digital cadastre, which are based on integrating old and new measurements, are mainly analytical, straightforward and aimed at resolving a specific situation rather than finding a comprehensive solution for reinstating the cadastral boundaries. A new unconventional approach that employs biological optimisation to attain unique, uniform and accurate coordinates under customary cadastral requirements - Genetic Algorithms (GAs) - is presented. This is a stochastic approach, originating in evolutionary algorithms, which is widely and successfully used in many other fields and disciplines. By mimicking biological processes, GAs offer an optimum solution obtained from a diverse range of possible initial solutions to a problem, by evaluating and evolving throughout a number of generations (iterations). The implementation of GAs principles in cadastral domain yielded good and promising results in a series of simulations performed on synthetic and real data. Based on these examinations it can be conclusively inferred that the GAs solution is more accurate than the conventional method - the coordinates are closer to their ‘true’ value than those obtained from the common Least Squares technique.

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4. Security of ownership versus public benefit: a case study for land taking for infrastructure in Greece, as an EU member state
Potsiou, C; Basiouka, S

This paper presents the results of a 4 year research (Internet, existing literature, interviews with experts from the public and private sectors, Ministry records) on the general legislative and technical aspects and the procedures implemented in Greece, an European Union (EU) member State since 1981. It is a study of compulsory land acquisition and is a case study focused on collecting and analysing recent information about land taking procedures and practices in Greece with an emphasis on current major highway projects. Included is a study of the legal framework; the legislative amendments adopted progressively through recent years; and the existing conflicts among the various Greek courts and the Court of Justice of the European Union and between interpretation of the Greek legislation and the practices in free market economies. Additional problems with the land acquisition process are investigated. This case study focuses on the investigation of emerged problems, and the legislative changes made, due to pressure for a number of major infrastructure projects for the 2004 Olympic Games and motorway projects commissioned by the Hellenic Ministry of Infrastructure, Transport and Networks. These consist of major transportation road networks in the areas of Northwestern Greece (Ionia Odos), North Greece (Egnatia Odos), Attica peninsula (Attiki Odos) and the Peloponnesus (Olympia Odos). An effort is made in this study to develop strategic recommendations for improving the protection of private property in Greece; harmonising land expropriation practices with the European approach; and for simplifying and accelerating the adjudication process and the achievement of more transparent and just compensation.

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5. A case study on local SDI implementation in Germany
Müller, H; Würriehausen, F

This paper presents a case study which highlights some aspects of local spatial data infrastructure (SDI) implementation in Germany. The study outlines the concrete situation as given in the South Western German State of Rheinland-Pfalz by discussing it in the context of the evolution at higher SDI levels represented by the INSPIRE initiative at the European level and by the GDI-DE initiative at the German national level. Special emphasis is given to the integration of communal SDIs within the local SDI level. Benefits of SDI application of land tools like urban planning, land-use regulation and property registration are shown. Integration of the communal SDI into the states’ SDI is illustrated.

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6. Data quality of Global Map and some possibilities/limitations for its wide utilisation for global issues
Idrizi, B; Meha, M; Nikolli, P; Kabashi, I

Global Map (GM) was born as a product to replace previous IMW (1:1,000,000) with a new map in digital form with the homogeneous standards for entire globe. The primary objective of GM is to contribute to the sustainable development through the provision of base framework geographic dataset as necessary for better understanding the current situation and changes of environment at a global level. The GM datasets encompass the entire globe at a scale of 1:1,000,000 (for vector data) and spatial resolution of 30 arc seconds (for raster data). Global Map with its consistent quality and data standards is a handy tool to monitor the environmental status at regional and global scale, which may have limited uses at national and local scales. It also provides a framework within which the local environmental problems can be modelled and analysed with appropriate data. Disaster prevention, disaster mitigation, preserving biodiversity, promoting regeneration processes of the ecosystem, etc. are some of GM targets. Due to fact that the GM data from geometrical point of view are basically partially topological and non-harmonised data coming from different sources (NMOs), our efforts for its utilisation for map compilation and spatial analyses resulted with limitations because of overlaps and gaps between the polygons, as well as non-spatial joint between the line objects. The GM specification allows to each participant to use different sources with different quality for different areas of their countries and for different layers. This type of definition of non-homogeneous accuracy without any process of data harmonisation in some way allows overlaps, gaps, and non-spatial joint of data not only between different countries, but the data within the same country and between different layers. The relation between the data of raster and vector layers, resulted with big differences, basically because of non-homogenous accuracy between the vector and raster data, and non-harmonised data, as well as because of the differences on the defining of the level zero from the participant countries. The above situation can be overcome by including the data harmonisation process as a necessary step during the process of preparing the GM data, which should be defined in GM specification. This process might be very difficult, because of some mentioned political problems above; however, it is a necessary step for better future of Global Mapping project and wide utilisation of GM data.

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7. Automatic georeferencing of non-geospatially referenced provisional cadastral maps
Siriba, D N; Dalyot, S

This paper presents a methodology for the automatic georeferencing of provisional maps that have no geospatial reference grid. The methodology, which is a modification of the generalised Hausdorff distance registration measure, entails an iterative ranking process that consists of a set of qualitative statistical quantification to evaluate the correspondence of two datasets (pixel and object), overcoming data ambiguities, including outliers and noise. The automatic methodology presented can replace the preliminary requirement for initial manual or semi-automatic georeferencing of non-geospatially referenced data that are prone to error. It is a preliminary step in an overall data integration approach intended to enhance the geometric quality of such positional-approximated provisional maps to be used as qualitative spatial data infrastructure. A comparison of the proposed automatic georeferencing with the commonly used manual process showed better results, both in the number of point correspondences identified and in the final geometric alignment of provisional cadastral maps with a reference topographic dataset.

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8. VGI in Cadastre: a Greek experiment to investigate the potential of crowd sourcing techniques in Cadastral Mapping
Basiouka, S; Potsiou, C

What make citizens participate in mapping projects? What motivates them to get involved in a non-hierarchical network of individuals who collect, edit and share geospatial data? Would they be willing to participate in cadastral mapping as an alternative way to speed up the cadastral survey and minimise the costs and errors which rise when traditional procedures allow limited owners’ participation? The answers are still ambiguous. However, it is a fact that the way geospatial data are used and the way citizens comprehend its importance have changed dramatically during the last years. The paper briefly gives an introduction on the evolution of Neogeography and the citizens’ involvement in spatial data collection, editing and uploading on the web, and of the introduction of the term volunteered geographic information (VGI) and its adoption by the scientific community. The paper then presents the first results of an academic research being compiled at NTUA in collaboration with FIG Com3 WG 3•2. focusing on the investigation of the potential for intergrading crowd sourcing techniques to create draft cadastral maps. The application area chosen for the experiment is the rural part of the village ‘Tsoukalades’, on the Greek island of Lefkada. Fifteen volunteer land owners participated to a weekend experiment and collected geospatial data for the delineation of their land parcel boundaries on a cadastral map; the spatial data were collected with the aid of a handheld GPS after a brief training; the resolutions from the interviews with the land owners and the resulting citizens’ cadastral map are presented.

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9. An agent-based model for simulating urban morphology: Sachnin as a case study
Fisher-Gewirtzman, D; Blumenfeld-Liberthal, E

In some sub-urban areas, planning the distribution of resources is a highly difficult mission that is often done in retrospect, as a response to the (illegal) development of new built areas. The Arab settlements in the Galilee are organic entities and can be perceived as organic ‘communities’. Their built morphology is unique and does not follow strict geometrical patterns. The streets in these settlements do not align, and there is no visible continuity of their morphology. The difficulty in predicting the development of these settlements challenges the ability of the local authorities to adjust their planning in terms of urban infrastructure and facilities. This leads to low maintenance of the urban systems. Computer simulation models that mimic the development of such settlements could help understand the development trends and support future alternative designs. This may lead to better control and distribution of urban resources by local authorities and thus to an improved quality of life of the residents. In this paper, the potential and possible use of a preliminary agent-based cellular automata model is illustrated. This model mimics the development of sub-urban Arab (organic) settlements in the Galilee. It can be used to identify the influence of various scenarios of top down urban planning on the built environment. For example, planners can use this model to study the influence of different transportation paths on the city’s development. This work is based on the perception of urban and sub-urban entities as complex ones. These systems fit the definition of complex as they are governed by many agents that act in space and time, and are motivated by various forces. The interactions between these agents control the evolution of the built environment. In a preliminary study, we considered Sachnin as a case study and identified diverse forces that influence the development of the organic Arab settlement. We developed a preliminary model based on the traditional patriarchal form of the Arab family, as its influence on the settlement’s development is very significant. We showed that identifying one of the most influential processes that are related to the Arab settlements leads to a better understanding of the urban evolution in terms of spatial distribution and morphological configuration.

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Survey Review 44, No 324. January 2012

1. Performance improvement of network based RTK GPS positioning in Taiwan
Yeh, T K; Chao, B F; Chen, C S; Chen, C H; Lee, Z Y

Upon the availability of fast and stable Internet access and the mature virtual reference station (VRS) technique, the network based real time kinematic RTK GPS technique, which overcomes the limitations of traditional RTK (single reference station) positioning, has become an important tool of survey engineering. Since 2004, a regional real time GPS network with 86 stations for expanding the effective range of cadastral measurement has been set up in Taiwan. Users can get VRS observations from the control centre via wireless Internet and acquire high quality positioning. In an experiment we conducted, we find that after applying proper coordinate transformation to the coordinates measured by network based RTK GPS positioning, three-dimensional coordinates with centimetre level accuracy can be achieved, with results for the horizontal direction generally better than the vertical direction.

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2. Comparison of measurement and position domain multipath filtering techniques with the repeatable GPS orbits for static antennas
Lau, L

Repeatable satellite orbits can be used for multipath mitigation in Global Position System (GPS) based deformation monitoring and other high precision GPS applications that involve continuous observation with static antennas. Multipath signals repeat when the GPS constellation does. There are two possible domains for repeat-time based multipath filtering. One is based on filtering multipath errors in the measurements and the other on filtering multipath contaminated positioning errors. If all satellites have the same repeat time, the performance in the two domains should be very similar. However, the repeat time for individual satellite may be different and this leads to possible differences in performance in the two filtering domains. The aim of this paper is to assess the performance of the two filtering domains on multipath mitigation for short baselines. Three roof-top data sets collected at University College London and a data set collected at two International GNSS Service high-rate stations are used in our performance assessment. Test results are analysed and insights into the two filtering domains are described in details in the paper. Our overall result shows that the performances of the two filtering domains on multipath mitigation are similar, which is about 40% improvement on positioning accuracy when comparing with no multipath filtering.

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3. Towards a real property cadastre in Croatia
Cetl, V; Roic, M; Ivic, S Mastelic

The fall of the Iron Curtain and the change of social and economic order in the East European countries, as in Croatia, have caused great alterations, especially in the perception of real property ownership and real property transactions. To be able to support the growing real property market it is necessary to reform the land administration system, because of the social ownership concept that was in practice over 50 years on the former Yugoslavia territory. Having recognised this challenge, Croatia invests enormous efforts and significant financial resources in order to modernise the land registration system as quickly as possible, so as to guarantee security of ownership and real property transactions. In this paper, an overview of the inherited cadastral system and current activities towards a modern real property cadastre is given.

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4. Combining surface deformation parameters referred to different terrestrial coordinate systems
Berber, M; Kutoglu, H S; Dare, P; Vanícek, P

Transformation of deformation parameters from one coordinate system to another is investigated. For a robust deformation analysis, in addition to transformation parameters, their covariance matrix ought to be transformed to the desired coordinate system. This provides a check on the transformed parameters. For this purpose, a simulated network is employed. Results show that the outlined approach works well.

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5. Frame transformation and geoid undulation transfer to GNSS real time positions through the new RTCM 3•1 transformation messages
Capilla, R; Martín, A; Anquela, A B; Berné, J L

Radio Technical Commission for Marine Services (RTCM) standardised messages play an important role in real time Global Navigation Satellite Systems (GNSS) applications such as navigation, positioning, civil engineering, surveying, and cartographic or cadastral production. One of the latest agreements on RTCM definitions contains the data fields for real time geodetic reference frame transformation and orthometric heights computation by received geoid undulations via internet protocol. These parameters can be generated dynamically by a GNSS data centre in a network of reference stations, encapsulated in RTCM messages and broadcasted to the rover location so they are centrally administered and the same frame transformations and geoid model are available to every user in the field, obtaining results in a local reference frame in real time. This paper summarises the functionality of the new RTCM 3•1 transformation messages, describes limitations and provides ideas about the possible use for solving specific problems. Test field campaigns are used to describe the real performance and usefulness of these new RTCM 3•1 messages.

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6. Influential factors for decimetre level positioning using ultra wide band technology
Mok, E; Lau, F; Xia, L; Retscher, G; Tian, H

The integration of wireless and satellite positioning technologies can provide positional information in both indoor and outdoor environments for various location based services and applications. Among different wireless positioning technologies, ultra wide band (UWB) adopts the time delay approach based on highly accurate clock synchronisation between transmitter and receiver antenna. High accuracy range measurement data can therefore be used to derive decimetre accuracy positions. Similar to other wireless technologies, the transmission of UWB signal is subject to interference when propagating through different media. In this paper, influential factors for the theoretical decimetre level positioning expectation of UWB are analysed with a pair of PulseOn P210 devices. Our investigations include signal attenuation in different scenarios of materials of obstruction, multipath and geometrical effects. From the analysis of field test and simulation results, we conclude that UWB can generally achieve better than 0•5 m (95% confidence level), the accuracy of which agrees with specifications of the UWB real time positioning systems (RTLS) available on the market, and field test results of a UWB RTLS conducted by Mok et al. It is essential that UWB device be set up at a higher position to avoid the influence of multipath. When setting up the UWB location system, special attention should be paid to the location of the sensors in weak geometrical strength areas, such as tunnels and narrow corridors.

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7. Levelling in antiquity: instrumentation, techniques and accuracies
Stiros, S C

Certain major ancient engineering constructions, such as aqueducts and qanats, testify to high accuracies in the computation of elevation differences obtained using primitive levelling instruments. Based on the typology of ancient levelling instruments and the analysis of certain key ancient structures such as the (Eupalinos) tunnel at Samos Island (Greece), it became possible to specify the accuracy, and especially the measuring techniques and procedures of levelling in antiquity, ignored so far by non-professional investigators. Ancient levelling techniques were derived on the basis of trials and errors over past centuries and include standard length sighting distances (revealing that ‘cord stretching’ may also indicate levelling), stadias with fine focussing on sliding targets adapted to the level field of view, two-way measurement in levels and stadias, repeated and redundant observations in loops, measurements by skilled professionals. These techniques permit to limit and randomise systematic errors and to obtain accuracies up to a few centimetres per kilometre are likely to indicate a real theory of error propagation and are reminiscent of the techniques used in our days in extraordinary projects (the alignment of the CERN colliders, etc.).

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8. Surveying education at the New Zealand National School of Surveying
Coutts, B J; Strack, M S

The School of Surveying, University of Otago, continues to successfully offer a top quality professional degree programme for the New Zealand survey profession. It is actively looking to add other more specialised degrees, to allow for the recruitment of more students, to promote more obvious postgraduate opportunities and to follow a trend to more diverse professional engagement. At the same time, there is a renewed focus on enhancing research output to complement the quality teaching programme. This paper briefly outlines the origins of the New Zealand educational system for surveyors and discusses in more detail the suite of programmes and courses that the School of Surveying at the University of Otago offers to those interested in a career in the collection, manipulation, organisation, storage and interpretation of data related to land, land based resources, the sea bed and their use in the development of the built environment. The options open for professional recognition for these graduates are then discussed. New Zealand surveyors continue to gain employment in a variety of subdisciplines in all corners of the world. They carry with them the considerable reputation of surveying graduates from the University of Otago and land surveyors from New Zealand.

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9. Integer estimation methods for GPS ambiguity resolution: an applications oriented review and improvement

Xu, Peiliang; Shi, Chuang; Liu, Jingnan

The integer least squares (ILS) problem, also known as the weighted closest point problem, is highly interdisciplinary, but no algorithm can find its global optimal integer solution in polynomial time. We first outline two suboptimal integer solutions, which can be important either in real time communication systems or to solve high dimensional GPS integer ambiguity unknowns. We then focus on the most efficient algorithm to search for the exact integer solution, which is shown to be faster than LAMBDA in the sense that the ratio of integer candidates to be checked by the efficient algorithm to those by LAMBDA can be theoretically expressed by rm, where r<=1 and m is the number of integer unknowns. Finally, we further improve the searching efficiency of the most powerful combined algorithm by implementing two sorting strategies, which can either be used for finding the exact integer solution or for constructing a suboptimal integer solution. Test examples clearly demonstrate that the improved methods can perform significantly better than the most powerful combined algorithm to simultaneously find the optimal and second optimal integer solutions, if the ILS problem cannot be well reduced.

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10. Modelling post-seismic displacements in Thai geodetic network due to the Sumatra-Andaman and Nias earthquakes using GPS observations
Panumastrakul, E; Simons, W J F; Satirapod, C

It is evident that the 2004 Sumatra-Andaman, 2005 Nias and 2007 Bengkulu earthquakes caused significantly large co-seismic and post-seismic displacements all over the South-East Asian region. The Thai geodetic network has been severely affected by the 2004 and 2005 earthquakes. Largest post-seismic horizontal displacements were observed in the southern part of Thailand, while moderate and small displacements were seen in the central and northern parts of Thailand. This paper will analyse the GPS observations obtained by the Royal Thai Survey Department GPS campaigns up to the end of 2009. The post-seismic displacements have been shown to follow a main direction which is towards the rupture area. A simple filtering technique is proposed to remove noise from the post-seismic displacements prior to the fitting of the post-seismic displacements with the logarithmic decay function. As a result, the τ log values in the logarithmic decay function at each point were found to be more consistent in both north and east directions. The new fitting results can therefore be used to estimate the coordinate of the zero-order Thai geodetic network to any epoch with millimetre accuracy.

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