2023 Abstracts


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Email: Peter Collier


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Survey Review 55, No 393. November/December 2023

1. Median robust nonlinear weighted total least squares estimator of nonlinear EIV models: three algorithms
Chuan Hu, Chenghong Li, Chongyang Zhang, Lidu Zhao, Xiaomeng Fan, Yusen Zhou, Hongzhou Zhu & Zheng Chen

To improve robust estimation performance of fully correlated nonlinear error-in-variables model, three median robust estimate methods are discussed on base of Nonlinear Weighted Total Least Squares (NWTLS), namely, median parameter method, median parameter initial value method and median variance method. After the discussion of the median robust estimation theory and the derivation of the calculation formula of the three median robust estimation methods, three iterative algorithms are developed. Through two nonlinear regression examples, four schemes including no artificial outliers, different location of outliers, different degrees of correlation, and different ratios of outliers are adopted, which proves the feasibility and effectiveness of the proposed algorithm. The experimental results show that from the statistical point of view, although the three median methods have different antioutlier effects for different nonlinear models, they are more effective than RNWTLS and NWTLS; the robust estimation results of three median methods are related to the functional model.

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2. A combination constellation mode of kinematic PPP with priori constraints for determining ocean tide loading displacement
Hong Zhao, Jiwei Zhu, Zhi Liu, Guangwei Jiang & Yangyang Sun

To improve the efficiency of estimation of deriving OTLD parameters with higher accuracy and take full advantage of multi-GNSS data, we investigate the potential of using global ocean tide model predictions as prior constraint for GLONASS and combined GPS+GLONASS kinematic precise point positioning (PPP), analyzing one year of GPS and GLONASS data from 20 Crustal Movement Observation Network China (CMONC) sites distributed along China coast. Seven global ocean tide models predictions are employed as prior constraint in kinematic PPP. Compared with the results of GPS-only kinematic PPP with priori information constraint, the result shows that GPS+GLONASS and GLONASS can improve the accuracy of OTLD estimates more than 40% in three components over GPS. The comparison of the effect of OTLD estimates on long-period signals in position time series shows that the correction effect of the kinematic PPP with seven different priori information constraint estimates is all as same as the reference model in three components.

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3. A precise geoid model of Bosnia and Herzegovina by the KTH method and its validation
Dževad Krdžalić & Ramazan Alpay Abbak

We compute the first gravimetric geoid model for Bosnia and Herzegovina (BHG2022) based upon the KTH method and additive corrections. The BHG2022 is computed with the help of 34,820 terrestrial gravity points and a digital elevation model produced by the Shuttle Radar Topography Mission. The gravity data is gridded onto a 0.02 arc-degree resolution via the nearest neighbour interpolation method. ITU_GGC16 and ITG-Grace2010 models are utilised to provide long wavelengths of gravity field up to 280 and 180 maximum degree/order in the geoid computation, respectively. On the basis of an external evaluation by 609 Global Navigation Satellite System (GNSS)-levelling points homogeneously distributed over the country, the accuracy of the BHG2022 is estimated to be 5.65 cm absolutely. This is the most precise geoid model ever seen in this territory. The result highlights the significant effect of all gravity data obtained from various sources on the accuracy of the geoid model.

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4. An alternative to derive ionospheric and tropospheric SSR corrections for PPP-RTK using adaptive constraints
Paulo Sergio de Oliveira Jr, Laurent Morel, João Francisco Galera Monico, Stéphane Durand, Frédéric Durand & Lucas dos Santos Bezerra

PPP-RTK (Precise Point Positioning – Real Time Kinematic) is a positioning method by GNSS (Global Navigation Satellite Systems), based on the SSR (State Space Representation) concept. One challenge for the fast convergence of PPP-RTK solutions in real-time applications is the mitigation of atmospheric effects (troposphere and ionosphere). Thus, using atmospheric models, PPP solutions can achieve accurate positions and shortened initialisation time. Such performance depends on the topology of permanent station networks and atmospheric conditions. The main objective of this contribution is to study the PPP-RTK and the optimised infrastructure in terms of costs and benefits to realise the method using atmospheric corrections.

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5. Performance of low-cost GNSS equipment in monitoring of horizontal displacements
Güldane Oku Topal, Mustafa Fahri Karabulut, Nedim Onur Aykut & Burak Akpınar

To investigate theperformance of low-cost GNSS equipment in monitoring horizontal displacements ANN-MB-GNSS and A10 antenna were installed on Zeiss-BRT-006 reduktionstachymeter, which can move with mm sensitivity in the horizontal plane. Ten days of static data were recorded with U-Blox-ZED-F9P-02B-GNSS receiver and processed with CSRS-PPP online-service. Considering theobservation period(12,6,3,1h), nine horizontal displacement magnitude tests were performed.Inaddition, GNSS-PPPAR solution percentages, multipath and signal-to-noise ratio values were considered. The results reveal that 20mm displacement can be determined (6mmRMSE) using the PPP approach based on a 3-hour observation period with A10antenna and 30mm can be determined (15mmRMSE) with UBX antenna with a 6-hour observation.

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6. Accuracy assessment of the SRTM2gravity high-resolution topographic gravity model in geoid computation
Bihter Erol, Muhammed Raşit Çevikalp & Serdar Erol

The accuracy of the SRTM2gravity high-resolution topographic gravity model is tested in this study. Complete Bouguer anomaly datasets calculated with classical formula in planar approximation and using the SRTM2gravity model in spherical approximation were compared in the study area. Two geoid models computed using free-air anomalies, which were restored from each Bouguer anomaly datasets, were compared to each other and they were validated at GPS/leveling points. In the mountainous part of the area, two geoid models differ by up to 4 cm. Following GPS/leveling validations, the geoid models provided nearly the same accuracy (∼4.2 cm). In conclusion, the accuracy of the SRTM2gravity model data was found sufficient to use in gravity reduction and it is recommended as a ready-to-use product in the area for gravity interpolation/gridding and geoid determination purposes.

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7. Single-station quad-constellation GNSS regional ionospheric modelling for navigation
Guang Liu, Changsheng Cai & Yanjie Li

Conventionally, regional ionospheric models (RIMs) are established using GNSS at multiple stations. However, this will severely rely on the availability of the local GNSS observation network. In this study, a single-station quad-constellation GNSS regional ionospheric modelling (SQG-RIM) approach is proposed by establishing the RIM with the GPS/GLONASS/BDS/Galileo observations at a single station. To facilitate its application, an algorithm is further proposed to divide the entire modelling region into the core area and the non-core area. Compared with the global ionospheric map (GIM), the SQG-RIM in the core area can increase the ionospheric error correction rate by about 9%. Further, the SQG-RIM is applied to single point positioning (SPP) using a differentiated weighting scheme for different signal-passing areas. Test results indicate that the three-dimensional quad-constellation SPP accuracies are improved by 57% and 52% after applying the SQG-RIM as compared to the Klobuchar and GIM models, respectively.

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8. Performance investigation of GLONASS in the static PPP technique with independent short measurement times using online processing services
Ömer Yurdakul

The precise point positioning (PPP) technique, which is still being developed, provides position accuracy at the centimetre (cm) level and is widely employed in scientific research. In the PPP technique, cm-level accuracy can be achieved by evaluating raw data obtained from a single Global Navigation Satellite Systems (GNSS) receiver using precise satellite orbit and clock correction data and other parameters. The majority of studies in the literature are based on 24-hour data obtained from the International GNSS Service (IGS) and similar stations. However, there are fewer articles in which analyzes based on short-term measurements are taken. In this study; the effect of GLONASS on the static PPP technique was investigated with independent short measurement times. For this purpose, measurements were made at 7 different test points on consecutive days using a single GNSS receiver. A 4-hour static measurement was made at each test point. The data obtained were processed in two different scenarios, only GPS and GPS + GLONASS using the Canadian Spatial Reference System – PPP (CSRS-PPP) and Trimble RTX online process software. The processes were completed at 4, 2, 1, and 0.5 h. As a result of the analysis, it has been observed that GLONASS improves the results by 76%, but negatively affects some solutions (24%). It was also observed that GLONASS drastically reduced the outlier values. With this study, it is aimed to show the accuracy that users who make short-term measurements with a single GNSS receiver can be achieved in the static PPP technique by using GPS + GLONASS systems, with repeated measurements.

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Survey Review 55, No 392. September/October 2023

1. Implementation of the land reallocation problem using NSGA-II and PESA-II algorithms: a case study in Konya/Turkey
Zeynep Haber, Harun Uguz & Huseyin Hakl

Land consolidation is one of the essential tools to increase productivity in agricultural production. The most important, complex, and time-consuming step is land allocation among the land consolidation stages. For these reasons, it is inevitable to use computer technology to optimize this process. This study used reallocation models based on PESA-II and NSGA-II optimization algorithms to solve the reallocation problem. The methods were compared with the optimization algorithms in the literature and the conventional method obtained by the technician. The applied algorithms have achieved successful results by parcel number, average parcel size, and reallocation cost.

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2. Data lifecycle of underground land administration: a systematic literature review
Bahram Saeidian, Abbas Rajabifard, Behnam Atazadeh & Mohsen Kalantari

Underground Land Administration (ULA) plays a paramount role in recording, registering and managing underground ownership boundaries and rights, restrictions and responsibilities associated with underground assets. 3D digital models provide a great potential to modernise ULA as it is evident in research studies. Several steps, from data acquisition to the use of underground land data have been considered by studies to support 3D ULA. These steps form the ULA data lifecycle. This paper provides an overview of methods, techniques and tools used in different steps of the ULA data lifecycle and identifies research gaps, challenges, and potential opportunities for future studies.

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3. Discontinuity set extraction from 3D point clouds obtained by UAV Photogrammetry in a rockfall site
Murat Yakar, Ali Ulvi, Abdurahman Yasin Yiğit & Aydın Alptekin

Rockfall event is common on rocky terrain, and it threatens people. Recent advances in remote sensing technologies allow us to model the terrain with high accuracy and resolution. In this study, we show the application of modeling a rockfall site in three-dimensional (3D) using an unmanned aerial vehicle. The acquisition of information about discontinuities in the rock masses using 3D point clouds is vital to characterize rockfall dynamics. We obtained 3D spatial information and point clouds of a rocky slope from acquired images. We extracted 10 discontinuity sets from the 3D model as they have significant effects on the failure mechanism. Details in mapping discontinuities have improved significantly with the help of point clouds. The results are beneficial for modeling the terrain of inaccessible areas with high resolution and obtaining information from those areas. This paper shows how can point cloud analysis be applied to characterize discontinuity sets.

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4. The Oblique Mercator for engineering and survey
D. Abbey, L. Woolhouse & W. Featherstone

The Oblique Mercator (OM) has been the runt in the family of conformal coordinate projection where its particular attribute of arbitrary orientation has been largely ignored. It is proposed that the Oblique Mercator, as a conformal projection, is well-suited to bridge the gap between a conventional north-oriented projection and the family of engineering grids that are unit-scaled and arbitrarily oriented improve the management of coordinate reference systems (CRS) between GIS and CAD/BIM software that has been, and remains, a significant cause of inefficiency for engineering design and construction, and for plane surveying. Issues relating to the selection of an optimal set of HOM projection parameters are discussed, including a new method to transform an existing engineering grid into an optimised HOM grid.

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5. Derivation of 9-parameter affine 3D geodetic datum transformations
A. C. Ruffhead

This paper proposes a new method of deriving 9-parameter affine 3D datum transformations by ordinary least-squares. Unlike previous methods, it covers all versions of the transformation. Initially, an ‘average’ scale factor is computed by distance analysis. Removing the scaling effect, the ‘RIGOPT’ subroutine is applied to optimise the rigid transformation that consists of 3 translations and 3 rotations. Using an equivalent enlargement hypothesis, the number of scale factors is increased to 3 by a short series of single-search-direction optimisations. The minimisation of residuals is verified by enclosing-interval analysis. The case studies cover datasets in Western Australia, Great Britain and Sweden.

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6. Calculating the differences of VTEC values obtained by altimetric and GNSS observations in coastal areas
Miloš Marković, Oleg Odalović & Marko Stanković

The difference between the VTEC values obtained from the Global Navigation Satellite System (GNSS) and satellite altimetry is much more noticeable over the ocean and the sea due to less coverage of the GNSS observations. Previous research shows that differences can go up to 15 TECU. The main problem is calculating VTEC from raw data which is ambiguous. This paper presents filtering methods for estimating the differences between mentioned datasets. By using this solution, it is possible to achieve better accuracy on a global estimation of the deviation. The International Reference Ionosphere values were used for validation of the results.

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7. Policy and legislative gaps in customary land revenue management in Ghana: emerging issues from Ashanti Region, Ghana
Mustapha Okyere, Leonard Adusu, Pascal Zini, Kennedy Zinale & Bankolay Theodore Turay

This study examined the existing legal framework for mobilizing, distributing, and utilizing customary land revenue in Ghana. It combined a review of the regulatory framework on land revenue management and face-to-face interviews with Officers of the Administrator of Stool Lands with the view to identifying the gaps inherent in these regulations. The study found that the lack of legislative clarity on the mobilization and application of stool land revenue has been responsible for the misappropriation of funds by beneficiaries. Legislative reform is recommended to remedy the inherent gaps in the land revenue management regime in Ghana.

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8. Citizens’ satisfaction with the land registration procedure: evidence from Ha Dong district, Hanoi, Vietnam
Quang Cuong Doan

This study aimed to discover citizens’ evaluation and satisfaction with land registration procedures. Using Hanoi as a case study, interviews were done at the Land Registration Office to clarify the satisfaction with land registration. The results show that the satisfaction rate was 74.6%. Collected data were analyzed through machine learning algorithms to find the factors affecting satisfaction. The results indicate that the number of times citizens go to agencies and waiting time are the most significant factors contributing to citizens’ satisfaction. The government should design and unify single points for applications, develop a digital-based cadastral database, enable online payment, and modernize facilities to improve the citizens’ satisfaction.

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Survey Review 55, No 391. July/August 2023

1. New approach to shape elongation estimation based on the Delaunay triangulation
Mariusz Zygmunt, Robert Szewczyk, Jacek Gniadek & Jarosław Janus

Automatic determination of shape parameters is still a current issue due to the dynamic development of technologies requiring image or geometric data analysis. The research described in this paper presents a new approach to the estimation of shape elongation and the calculation of lengths of shapes whose boundaries may be represented by polygons. The proposed algorithm is based on the Delaunay triangulation. The new approach may play a significant role in practical applications concerning spatial pattern analysis, land fragmentation and efficiency of projects focused on land consolidation and landscape fragmentation analysis.

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2. An adaptive approach to optimise regional geoid undulation model for engineering applications
Chun-Jia Huang & Jen-Yu Han

Geoid undulation model is typically used for the conversion between GNSS obtained ellipsoidal heights and their orthometric counterparts. In this study, an adaptive approach for optimizing regional geoid model based on global geoid model and local GNSS/leveling measurements is presented. A rigorous sequential least squares approach coupled with an adjustable criterion is used for identifying appropriate observables so that an optimized model that fulfills a predefined quality level can be automatically produced. It has been demonstrated that a city scale geoid undulation model with a quality level around ± 14mm√km can be obtained by applying the proposed approach.

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3. Investigation of the effect of height difference and geometry of GCP on position accuracy of point cloud in UAV photogrammetry
Kemal Ozgur Hastaoglu, Hacer Sura Kapicioglu, Yavuz Gül & Fatih Poyraz

In this study, the effect of the height difference, geometry, and number of GCPs on the positional accuracy of point cloud was investigated in UAV photogrammetry. It has been determined that the topographic change of the study area, the geometric structure of GCPs, and the distance between GCPs are the most important factors in GCP network design. It was observed that the GCP network design is more important than the number of GCPs in the UAV Photogrammetry method to increase the positional accuracy.

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4. Study of crustal deformation in Egypt based on GNSS measurements
S. A. Younes

This paper presents the study of crustal movements and their relation to earthquake activities within Egypt using the GNSS and seismicity measurements. Fourteen campaigns of GNSS measurements have been collected, processed, and adjusted. The collected data of about 50 permanent and campaign GNSS stations, which covered the whole geographic area of Egypt covering about 12 years, were used. The collected data are utilised using differential GPS with surrounded IGS stations by Bernese software V 5.0. The results of the deformation analysis indicate that northern Egypt is deformed more than the southern part.

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5. Evaluation and comparison of the performance of BDS-3 space-borne atomic clocks
Yue Mao, Xiaoyong Song, Qinghua Zhang, Rengui Ruan & Long Wang

At present, most of the space-borne atomic clocks used by the major global navigation satellite systems include rubidium atomic clocks, passive hydrogen master (PHM) clocks and cesium atomic clocks. The new independently developed space-borne rubidium atomic clocks and PHM clocks on BeiDou Global Navigation Satellite System (BDS-3) are important hardware improvements. In this paper, performances of new Beidou domestic atomic clocks are evaluated using precise clock offset data from September 2019 to September 2021 and compared with the mainstream space-borne atomic clocks of other satellite navigation systems. The results show that the BDS-3 space-borne PHM clocks have low drift rate and high stability at 86400s interval, which respectively reaches 8.26 × 10−16 and 5.13 × 10−15. These performances are only slightly lower than Galileo PHM clocks. The frequency stability at 86400s interval of BDS-3 rubidium clock is up to 9.03 × 10−15, which is 27.76% higher than GPS rubidium clocks.

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6. Improved chord method for the direct and inverse problems of the distances and azimuths on the reference ellipsoid
Wei Quan, Jianjun Zhang & Chen Liu

Through transformation from geocentric to topocentric space rectangular coordinate system and taking advantage of the plain geometrical relationships from the chord between two points on the ellipsoidal surface, the problems of the distances and azimuths on the reference ellipsoid can be converted to several elementary equations and corresponding corrective terms. Based on this, an improved chord method has been proposed in the article. Numeric experiments have validated that the new algorithm can be effective for arbitrary distances. Moreover, the solution can also be operational without singularity in the polar or equatorial regions, in the situations where the difference in longitude is 180°, and in other special cases. And with suitable corrections, the improved method can be prospectively applied to other problems of distances and azimuths with corresponding precision.

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7. Improved deformation modelling of structures by least-squares variance component estimation based on multi-sensor data integration
Marzieh Jafari

In this contribution, to improve the deformation modelling based on data integration, the LS-VCE algorithm is proposed by obtaining a stochastic model of input multi-sensor data. So, one can achieve the accurate variance-covariance matrix of multi-sensor observations to participate in iterative least-squares. A practical application was made for the settlement observations from geotechnical settlement-meters and geodetic levelling (respectively known as internal and external sensors) to model the surface settlement variation of the Karkhe earth-dam. The determined variance component shows less contribution of the geotechnical settlements in the deformation modelling. An achievement of this paper is that the LS-VCE method improves the integration of the geotechnical with geodetic data by estimating an optimal stochastic model resulting in deformation model optimization. Validation results of estimated surface settlements on the check-points show an RMSE of about 3 cm and a relative-error of about 14%, which indicates the success of the modelling.

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8. Point disposition of the conditional benchmark network and the railway curve elements
K. Mamonov, O. Saiapin, Y. Orel, S. Kamchatnaya & O. Pustovoitova

Control of geodetic parameters is very important for traffic safety on the railways. Such control must be performed regularly because of the deviation of the track axis due to train traffic. The purpose of the article is the development of a mathematical rationale for the placement of railway benchmarks for the creation of the ‘own’ conditional benchmark network of the railway. These permanent repers are the basic points for both the construction stage and operation stage. The method is described and the curve coordinates from any point of the conditional benchmark network of the railway have been obtained.

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Survey Review 55, No 390. May/June 2023

1. Allowing context to speak: the progressive case study method for cadastral systems research
Simon Hull & Jennifer Whittal

For research involving customary land rights, ‘context is key’ because every context brings specific nuances for consideration. Failure to account for context runs the risk of irrelevance, unintended consequences and/or failure. We present a research method that allows context to speak: the progressive case study. The approach combines deductive case study with inductive grounded theory approaches. The results are used to propose a framework for guiding cadastral systems development in customary land rights contexts. This paper presents the methodology, which should be useful for researchers, NGOs and multinational organisations doing development programming in developing contexts.

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2. Optimisation of doppler search space to improve acquisition speed of GPS signals
K. Bahmani, M. Nezhadshahbodaghi & M. R. Mosavi

The acquisition section has some serious problems to increase the speed of acquiring the Global Positioning System (GPS) signals. In this study, we propose three new methods to optimise the Doppler search space and improve the acquisition speed of the GPS signals. The experimental results represent that our proposed methods have a superior performance compared to the conventional bin-fixed method so that the first (sub-frequency band), second (multi-frequency bins), and third (integration of the first and second methods) suggested methods outperform the bin-fixed method in terms of the execution time and computational complexity by approximately 26–19%, 33–19%, and 36–20%, respectively.

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3. Temporal GIS models for cadastral data management: the knowns, unknowns and future
J. Mango, J. Ngondo, D. Xu, D. Zhang & X. Li

Numerous temporal GIS models for cadastral data management have been proposed, and to understand the state of their art, a study that critically assesses their designs is needed. This study reviewed 11 models and noted that except with earlier designs; most of the reviewed models could store temporal land parcels with their tracks of changes. However, they lack to maintain the semantics of their data, valid times and potential records of changes, and the alternative techniques to accelerate queries. Thus, a semantical and bi-temporal modelling framework is proposed. Future studies could use the framework and focus on implementation designs to obtain more robust models.

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4. Field comparison of the total station-based QDaedalus and the zenith telescope-based CODIAC astrogeodetic systems for measurements of the deflection of the vertical
Müge Albayrak, Daniel Willi & Sébastien Guillaume

The precision and accuracy of a Leica MultiStation 60-based QDaedalus astrogeodetic measurement system are determined through observations at two locations in Switzerland. The precision of the QDaedalus was determined as 0.1″ for the N-S and E-W deflections of the verticals (DoVs) through 118 series of observations collected over 13 nights (in a 44-day observation period) at the HEIG-VD test station. The accuracy of the QDaedalus system was established by simultaneous parallel observations over two nights using the CODIAC system at the Zimmerwald Observatory. The differences between them were found to be 0.09″ and 0.02″ for the N-S and E-W DoV components, respectively. From these results, the accuracies of both DoV components can be interpreted as 0.1″. We also found a large systematic trend in the observed N-S DoV data at the HEIG-VD test station (0.008″/day). This study is the most extensive thus far for determining the precision and accuracy of the QDaedalus system for astrogeodetic measurements; it is also the first time that QDaedalus system’s accuracy has been established using parallel observations.

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5. Accuracy assessment of the Croatian height transformation model
Blaženka Bukač, Ivan Razumović & Nevio Rožić

The Croatian height transformation model (HTMV) enables the transformation of absolute heights of discrete points with known horizontal positions from the Trieste 1875 reference system used throughout the former Republic of Yugoslavia and in Croatia known as HVRS1875 to the new height reference system of the Republic of Croatia (HVRS71) and vice versa. The HTMV is realised as a grid transformation model based on separate modelling of datum and distortion components comprised in height differences. The quality of the transformation model is assessed by comparing the difference in height values at benchmarks that were not used in the model derivation against height differences at the benchmark locations interpolated from the model. The results indicate a high external and internal accuracy of the transformation process, which points to the adequacy of the HTMV utilisation for engineering purposes.

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6. Digitisation and analysis of historical vertical deflections in India
W. E. Featherstone & R. Goyal

We describe the [somewhat tedious] process of digitising from a 1955 report that lists over 1000 vertical deflections in India and some surrounding countries. It involved error-checking with closed-loop tests and resolution of an ambiguity surrounding the meridional vertical deflection at the Kalianpur origin of the datum. We transformed these Kalianpur coordinates to geodetic coordinates on geocentric datum to compute absolute vertical deflections. However, due to many changes to the Everest spheroid due to different feet to metre conversions and readjustments of the Kalianpur datum, we were restricted to using the abridged Molodensky transformation parameters for the 1975 Kalianpur datum and Everest 1956 spheroid based on only seven common points from the WGS84 technical manual. We compared these transformed absolute vertical deflections with EGM2008 and GGMplus (for both models: meridional standard deviation: ∼±2″; prime vertical standard deviation: ∼±3″), showing that the effort of digitisation and scrutiny of historical geodetic data is indeed worthwhile.

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7. Ambiguity resolution method using BDS/INS model
F. Wu, J. Zhao, J. Xue & D. Li

Due to the highly dynamic changes of the environment, the frequent loss of signal will seriously reduce the accuracy of realtime dynamic positioning. Meanwhile, the ambiguity resolution for medium/long baseline is more affected by atmospheric delay. To solve this problem, an Inertial Navigation System (INS) assisted Beidou Navigation System (BDS) medium/long baseline partial ambiguity resolution (PAR) method is designed. Firstly, constructing the BDS/INS tight integrated system that uses INS provided initial information to ambiguity resolution when the signal outages. Secondly, the atmospheric delay constraint is introduced to improve the precision of float ambiguity. Finally, the PAR based on the elevation angle information is applied to enhance fixed speed and accuracy. The vehicle experiments show that the proposed algorithm can quickly fix the ambiguity of medium/long baseline when the satellite signal outages for a short time, and improve the positioning accuracy of medium/long baseline in the dynamic environment.

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8. Establishment of Taiwan’s standard operating procedure for network-based RTK in cadastral surveying
Ta-Kang Yeh, Hsuan-Chang Shih, Chuan-Sheng Wang & Tzu-Yi Lien

Taiwan completed construction of GNSS reference stations for the network-based RTK system in 2007. The legal mode of operation used in Taiwan requires that each point be repeatedly observed for at least two observation sets separated by 60 min. This study presents a simplified field operating procedure, which measures 10 epochs of fixed solutions during each observation set and reinitializes observations 10 times. In addition, the national and local network-based RTK system were used. The average horizontal positioning accuracies were 1-3. Finally, a workflow is presented for using the network-based RTK to measure the control points in cadastral surveys.

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Survey Review 55, No 389. March/April 2023

1. Modelling and integrating public-law restrictions on urban areas for future cadastral system of Turkey
Arif Cagdas Aydinoglu, Rabia Bovkir & Sahin Il

The importance of evaluating cities with historical, environmental and liveability parameters have become critical for effective urban management. Modern cadastre and land administration need to register Public-Law Restrictions (PLRs) to ensure the completeness of various transactions. To develop a comprehensive PLR data model for real estate management integrated with National GDI models, this study investigates the urban-related PLRs. An interoperable data model was designed within the Management-Restriction-Regulation Zones data model as an extension with relation to the Cadastre data model. In future cadastral applications, all property-related restrictions can be accessible as in case of the designed data model.

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2. Identifying critical factors to enhance SDI performance for facilitating disaster risk management in small island developing states
Gregorio Rosario Michel, María Ester Gonzalez-Campos, Fernando Manzano Aybar, Teodoro Jiménez Durán & Joep Crompvoets

Small Island Developing States (SIDS) are highly exposed to disaster risk events that frequently overwhelm their capacity to generate and share spatial information to reduce human–economic losses. The Spatial Data Infrastructure (SDI) has been widely implemented to support information sharing and management in different domains. In this paper, we aim to identify critical factors to enhance SDI performance to facilitate Disaster Risk Management (DRM) in SIDS. We make use of a three-round Delphi survey and Kendall W coefficient to assess consensus among 28 key international experts in SDI, surveying and DRM. Our results illustrate strong experts’ consensus on identifying a list of 23 most critical factors. We found that people and policy factors matter the most. The insights reported here would assist decision-makers to design roadmaps to enhance sharing of spatial knowledge to build more resilient SIDS and to support their achievement of the Sustainable Development Goals.

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3. Short-term satellite clock bias forecast based on complementary ensemble empirical mode decomposition and quadratic polynomial
Xiaorong Tan, Jiangning Xu, Hongyang He, Ding Chen, Yifeng Liang & Miao Wu

The nonlinear and nonstationary characteristics of satellite clock bias (SCB) have a harmful effect on the accuracy and stability of SCB forecast. To eliminate the influence of nonlinearity and non-stationarity, a hybrid forecast model was constructed that combines complementary ensemble empirical mode decomposition (CEEMD) and quadratic polynomial (QP), called CEEMD-QP. First, the SCB sequence is decomposed into several intrinsic mode function (IMF) components and one residual term by CEEMD. Second, permutation entropy (PE) and the correlation coefficient are used to quantitatively determine the IMF component with more noise and weak correlation with the original SCB signal. Finally, the SCB is reconstructed with the IMFs and residual components, and QP model is used to fit and forecast the clock bias. We adapt the observation part of ultra-rapid precise SCB data of GPS provided by IGS to forecast experiments. The results show that the CEEMD-QP method has obvious advantages of forecast accuracy and stability in short-term forecast.

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4. Assessing the extent of state regulation of surveying professions in Kenya
O. A. K’Akumu

This paper considers the regulation of three aspects of surveying profession namely, agency surveying, cadastral surveying, and valuation surveying in Kenya. The regulation boards are examined in the context of their enabling legislations. All the professions belong to one professional organisation, the Institution of Surveyors of Kenya (ISK), modelled in the like of self-regulation objectives of the Royal Institute of Chartered Surveyors (RICS). A review of the practice of professional regulations attempts to assess the level of state control in the regulation of these professions. Paper recommends injection of more self-regulatory culture in future.

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5. Developing a framework for assessing the efficacy of rural cadastral system in the Amhara region, Ethiopia
Adane Mehari Getie, Tadesse Amsalu Birhanu & Teshome Taffa Dadi

The fit-for-purpose rural cadastre has been implemented for several years in the Amhara region of Ethiopia. There are no internationally accepted methodologies to evaluate the efficacy of rural cadastral systems in developing countries. In this study, an evaluation framework was designed from the literature review and used to assess the quality of the rural cadastral system. A mixed research method was applied. Data were secured from the pertinent participants, and descriptive statistics was used to analyze the data. The findings indicated that the framework developed for the quality assessment was found to be an essential tool to evaluate the efficacy of rural cadastral systems. The study identified the strengths, weaknesses, opportunities, and threats of the cadastral systems of the Amhara region, which underpinned the understanding of the spatial, legal, and institutional arrangements and statuses. Further, this study identified sets of indicators and good practices of the system.

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6. A new algebraic solution for transforming Cartesian to geodetic coordinates
Jia-Chun Guo & Wen-Bin Shen

An exact and stable algebraic solution based on solving a quartic equation with respect to the cosine function of the reduced latitude is proposed to transform Cartesian into geodetic coordinates. The unique proper root of the equation appropriate to the transformation is chosen from all possible roots by rigorous analyses and the singular region of the transformation that in which there at least one component of the geodetic coordinates is indeterminate or non-single-valued characteristics are determined strictly. The new algorithm does not need any approximation and the instability problems incurred in other algebraic solutions are overcome. For practical applications, the algorithm performs comparably to that of [Vermeille, H., 2011. An analytical method to transform geocentric into geodetic coordinates. Journal of geodesy, 85 (2), 105–117.] and shows a certain superiority in the singular disc over Vermeille's algorithm.

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7. An experiment on the role of participatory GIS in the adjudication process of customary lands
Kwabena Asiama & Anthony Arko-Adjei

This study presents the results from an experiment conducted in two peri-urban areas of Northern Ghana using Participatory GIS (PGIS) to identify land tenure and use rights on customary and statutory lands. P-Mapping was used to uncover indigenous knowledge on the changes in land ownership, land use rights and land-use types over ten years. The paper finds that properly trained local people can reliably delineate and indicate land rights and land uses in their environment on photomaps with little support from professionals. The experiment results show that PGIS can accelerate land adjudication processes on customary lands.

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8. Performance analysis of BDS B1C/B2a PPP using different models and MGEX products
Mengfei Sun, Li Liu, Wei Yan, Jian Liu, Tong Liu & Guochang Xu

To assess the precise point positioning performance of the new BDS signals, the observation data of 56 MGEX stations for 30 consecutive days were used to carry out dual-frequency PPP experiments. The positioning results showed that the best positioning performance could be achieved with CODE precise products, followed by IAC, GFZ, and WHU products, with SHA products performing the worst. For Ionosphere-free and undifferenced and uncombined models, the performance of the two was comparable. In addition, our study indicated that station location and time were not the main factors affecting the performance of BDS-3 PPP.

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Survey Review 55, No 388. January/February 2023

1. The novelty hybrid model development proposal for mass appraisal of real estates in sustainable land management
Suleyman Sisman, Ali Utku Akar & Sukran Yalpir

In this study, a new methodology has been developed for a sustainable mass appraisal system. A mathematical model was created with the combination of the Cobb-Douglas and the linear regression model. With the Analytic Hierarchy Process (AHP) method, real estate value criteria were grouped and weighted in a hierarchical structure. The weights obtained with AHP were integrated into the coefficients regarding the criteria weights and densities in the Cobb-Douglas hybrid model. The new hybrid model was confirmed with the features and price equivalents of 435 parcels for sale from the market. Besides, the model analysis results were compared with the Multiple Regression Analysis (MRA) modelling using market prices. While creating the methodology, Geographic Information Systems (GIS) was used to organize the geographic and regional data of the region. After developing the new hybrid model, criteria groups that developed the model and relevant sub-criteria were evaluated using Pearson's correlation analysis.

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2. Filtering airborne LIDAR data by using fully convolutional networks
Abdullah Varlik & Firat Uray

The classification of LIDAR point clouds has always been a challenging task. Classification refers to label each point in different categories, such as ground, vegetation or building. The success of deep learning techniques in image processing tasks have encouraged researchers to use deep neural networks for classification of LIDAR point clouds. In this paper, we proposed a U-Net based architecture capable of classifying LIDAR data. The results indicated that our network model achieved an average F1 score of 91% over all three classes (ground, vegetation and building) for our best model.

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3. Comparison of different machine learning models for mass appraisal of real estate
Süleyman Sefa Bilgilioğlu & Hacı Murat Yılmaz

The present study aimed to compare five machine learning techniques, namely, artificial neural network (ANN), support vector machine (SVM), chi-square automatic interaction detection (CHAID), classification and regression tree (CART), and random forest (RF) for mass appraisal of real estate. Firstly, 1982 precedent data was collected throughout the entire study area for train and test models. Secondly, a total of 68 variables were considered for the mass appraisal. Subsequently, the five machine learning techniques were applied. Finally, the receiver operating characteristic (ROC) and various statistical methods were applied to compare five machine learning techniques.

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4. Performance investigation of Trimble RTX correction service with multi-GNSS constellation
Omer Faruk Atiz, Abbas Qader Shakor, Sermet Ogutcu & Salih Alcay

In the middle of 2011, Trimble introduced the RTX correction service to support RT-PPP applications. In this study, the performance of Trimble RTX correction service is investigated over a one-month period using five different GNSS constellations – namely, GPS-only, GPS + GLONASS, GPS + Galileo, GPS + GLONASS + Galileo, and GPS + GLONASS + Galileo + BeiDou. The results show that positioning accuracy and convergence time are significantly improved with the use of the multi-GNSS constellation compared with the GPS-only solution. The result of the converged positioning accuracy indicates that the GPS + GLONASS + Galileo + BeiDou combination improves the accuracy by 63%, 54%, and 60% for north, east, and up components, respectively, compared with the GPS-only solution. The mean convergence time is reduced by the GPS + GLONASS+ Galileo + BeiDou combination by 70%, 71%, and 38.6% compared with the GPS-only solution in the north, east, and up components, respectively. 1.2 (north), 1.5 (east), and 2.3 cm (up) root mean square errors (RMSEs) of converged positioning from the GPS + GLONASS + Galileo + BeiDou combination are computed.

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5. Comparative analysis of real-time precise point positioning method in terms of positioning and zenith tropospheric delay estimation
Omer Faruk Atiz, Salih Alcay, Sermet Ogutcu & Ilkay Bugdayci

The positioning performance of widely used real-time precise point positioning (RT-PPP) software packages BNC, RTKLIB, and PPP-WIZARD were tested in terms of convergence time and accuracy. The convergence time of PPP-WIZARD solutions is reduced by ambiguity resolution (AR). The GPS + GLONASS + GALILEO (GRE) mode improved the convergence time of GPS + GALILEO (GE) mode by 22.0%, 15.5%, 17.1%, and 11.4% for the BNC, RTKLIB, PPP-WIZARD (AR) and PPP-WIZARD, respectively. For the GRE mode, RMSEs of the BNC, RTKLIB, PPP-WIZARD (AR), and PPP-WIZARD software packages in the horizontal/vertical component are 3.8/5.6, 2.6/6.2, 3.3/6.5, 4.3/7.0 cm, respectively. In comparison with the IGS-ZTD (International GNSS Service ZTD), BNC, RTKLIB, PPP-WIZARD (AR), and PPP-WIZARD solutions show a mean bias of 0.28, −0.72, 2.80, and 2.83 cm, respectively in GE mode. The GRE mode reduced the RMSEs of the ZTD estimations of BNC, RTKLIB, PPP-WIZARD (AR) and PPP-WIZARD by 2.9%, 5.1%, 0.6%, and 0.4% respectively.

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6. Positioning performance of GNSS-PPP and PPP-AR methods for determining the vertical displacements
Burak Akpınar

This study investigates the accuracy of vertical displacements monitored by Global Navigation Satellite Systems (GNSS) precise point positioning (PPP) with float-ambiguity solution and with ambiguity resolution (PPP-AR). For this purpose, a simulation was designed. The static GNSS observations were collected at a test point during different observation times over seven periods involving vertical displacements produced with a precision of less than one mm. Each set of GNSS observations was processed with both GNSS-PPP and PPP-AR methods. The results revealed that RMS values of PPP-AR solutions are about twice better than RMS values of PPP solution for all observation times and all vertical displacement values.

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7. Investigating the latest contribution of BeiDou-3 FOC to GPS/GLONASS/Galileo PPP
Sermet Ogutcu, Yuksel Kama Erkavas, Abbas Qader Shakor & Haitham Talib Farhan

In this study, the latest contribution of the BeiDou-3 FOC satellites to GPS/GLONASS/Galileo/BDS-2 combined static and kinematic precise point positioning (PPP) is investigated over a one-month period in 2021 considering the three different cut-off angles (7°, 15°, and 30°). The results show that the contribution of BDS-3 to GPS/GLONASS/Galileo PPP is generally marginal for 7° and 15° cut-off angles. The largest BeiDou-3 contributions to static and kinematic positioning accuracy are found to be 9%, 6%, and 19% (for 3-h sessions with the 15° cut-off angle) and 9%, 15%, and 8% (with the 30° cut-off angle) for the north, east, and up components, respectively. The largest reductions in static and kinematic convergence time by adding BDS-3 to GPS/GLONASS/Galileo are found to be 13%, 10%, and 6% (for the 30° cut-off angle) and 17%, 7%, and 6% (for the 30° cut-off angle) for the north, east, and up components, respectively.

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8. Book Review: Land surveying in Ireland, 1690–1830 by Finnian Ó. Cionnaith, Dublin, Four Courts Press, 272 pp., €35.00/£30.00 ISBN 978-1-80151-014-1
Peter Collier

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