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Survey Review 49, No 352. January/February 2017

1. Multiple linear regression with correlated explanatory variables and responses
B. Li, M. Wang & Y. Yang

Different from the traditional linear regression model that captures only the errors of dependent variables (responses), this contribution presents a new multiple linear regression model where, besides the errors of responses, the errors of explanatory variables and their correlations with response errors are rigorously taken into account. The new regression model is typically a non-linear errors-in-variables (EIV) model, which is referred to as the error-affected and correlated linear regression (ECLR) in this paper. Considering the fact that only part of elements in design matrix A of the regression model are random, the authors express error matrix EA of A as a function of EX consists of all non-zero random errors. Then, the authors can easily formulate the stochastic model without the effect of non-random elements in A. An iterative solution is derived based on the Euler–Lagrange minimisation problem for ECLR. The authors further show that ECLR is very general and some of the existing linear regression methods, the ordinary least squares (OLS), the total least squares (TLS) and the weighted total least squares (WTLS), are the special cases. The experiments show that the ECLR method generally has a better performance than the OLS, TLS and WTLS methods in terms of the difference between the solution and the true values when the explanatory variables and responses are significantly correlated.

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2. Adaptive time-variant adjustment for the positioning errors of a mobile mapping platform in GNSS-hostile areas
J. Han & C. Lo

A mobile mapping system (MMS) utilizes global navigation satellite system (GNSS) and inertial navigation system (INS) techniques and thus makes possible a direct geo-referencing solution everywhere along its surveyed path. It is capable of acquiring a vast amount of spatial information in an efficient manner and is adopted in a wide variety of applications. However, when the GNSS signal is obstructed, its positioning solution can only rely on the INS observables, which acquire significant and cumulative errors over time. In this study, an adaptive time-variant adjustment model is proposed to compensate for the MMS positioning error in a GNSS-hostile area using ground calibration points. Based on the results from a case study, it illustrates that the positioning error of a mobile mapping platform in an urban area for a long time could reach a level of several metres because of GNSS signal obstructions. However, this error can be properly modelled and significantly reduced to a centimetre-level when the proposed approach is applied. Consequently, both the efficiency and reliability of the MMS applications in a GNSS hostile environment can be further guaranteed.

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3. Empirical comparison of the Geodetic Coordinate Transformation Models: a case study of Croatia
Matej Varga, Marijan Grgić & Tomislav Bašić

This paper presents empirical research on coordinate transformation models that enable coordinate transformations between the historical astro-geodetic datums and datums related to the European Terrestrial Reference System (ETRS), through a case study of the Republic of Croatia. Thirteen models were investigated for the transformation from the historical Croatian State Coordinate System (HDKS) to the Croatian Terrestrial Reference System (HTRS96): Molodensky 3 and 5 parameter (standard and abridged) conformal transformation models, 7 parameter transformation models (Bursa-Wolf and Molodensky-Badekas model), Affine transformation models (8, 9, 12 parameter), Multiple Regression Equation approach, and several transformation models that include extending of the aforementioned 7 parameter and 8, 9, 12 parameter Affine transformation models with distortion modelling. Most of the models were investigated for the first time over the Croatian territory. Analysis of transformation models performance was conducted using an independent data set of reliable geodetic points. The study provides mutual comparison of the models and their comparison with the official Croatian transformation model called T7D. Furthermore, the most appropriate transformation model(s) were defined regarding the required accuracy and the available resources for the coordinate transformation models implementation. In addition, the paper provides a brief theoretical background and equations of each transformation model and summarises the bibliography on the research topic.

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4. A comprehensive evaluation of GNSS- and CORS-based positioning and terrestrial surveying for cadastral surveys
R. Cuneyt Erenoglu

any Global Positioning System/Global Navigation Satellite System (GPS/GNSS) methods are applied to the cadastral survey after the rapid development of satellite-based positioning. These methods are reported to give efficiency, speed and economy compared to the conventional ones. In this study, it is aimed to comprehensively evaluate the most commonly used GPS/GNSS methods for cadastral survey. Furthermore, a median based comparison strategy was developed for the distribution of the results. The research results showed the difference of a few centimeters between the coordinates obtained from the terrestrial and the GPS/GNSS techniques. Furthermore, the developed robust criteria verified the compatibility of the results. It is clear that the GPS/GNSS based methods achieve high accurate output in real time and are well-matched with surveying standards in Turkey. In addition, the robust criteria appear to be a fast, effective and objective method to compare the results, especially for the height component.

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5. Performance analysis of precise point positioning using multi-constellation GNSS: GPS, GLONASS, Galileo and BeiDou
M. Abd Rabbou & A. El-Rabbany

We developed a new GNSS PPP model, which combines the observations of GPS, GLONASS, Galileo and BeiDou satellite navigation systems for precise applications. Both undifferenced and between-satellite single-difference (BSSD) ionosphere-free GNSS PPP models are developed. The contribution of the new GNSS observations is assessed compared with the existing GPS and GPS/GLONASS PPP using three-hours GNSS static data positioning results for several GNSS stations and four consecutive days. Inter-system biases between GPS and other GNSS systems are obtained as additional unknowns in the developed PPP filter. The results indicate that both GPS and GPS/Galileo PPP present comparable positioning accuracy level, which is attributed to the limited number of Galileo satellites. The additional BeiDou observations enhances the positioning accuracy after 15 minutes by 5 cm, 4 cm and 9 cm in latitude, longitude and altitude, respectively compared with GPS only positioning accuracy. However, the BeiDou only PPP results present less accurate positioning accuracy compared with the GPS only PPP. The multi-constellation GNSS PPP enhances the positioning accuracy by 8 cm, 6 cm and 11 cm in latitude, longitude and altitude, respectively Compared with the GPS PPP results. Compared with the undifferenced PPP results, the BSSD model enhances the positioning accuracy after 15 minutes for the different GNSS constellations based PPP. The GPS/Galileo PPP positioning accuracy improves by 30%, 27% and 10% in latitude, longitude and altitude, respectively and the GPS/BeiDou PPP positioning accuracy, enhances by 17%, 22% and 15% in latitude, longitude and altitude, respectively while the multi-constellation GNSS PPP positioning accuracy improves by 22% and 15% in latitude and altitude, respectively over the undifferenced PPP technique. Additionally, the BSSD model is found to be superior with respect to the convergence times for the different GNSS combinations based PPP over the traditional undifferenced PPP model.

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6. Introduction to the GNSS geodetic infrastructure in the Gulf of Mexico Region
J. Yu & G. Wang

lobal Navigation Satellite System (GNSS) technology has been frequently applied to coastal hazards studies. Some such hazards include sea-level rise, subsidence, coastal erosion, flooding and faulting. This study summarised the current GNSS geodetic infrastructure in the Gulf of Mexico (GOM) region, which consists of three fundamental components: (1) a dense Continuously Operating Reference Station (CORS) network that is open to the public, (2) a stable regional reference frame that is tied to the International GNSS Service reference frame of 2008 (IGS08) and (3) sophisticated software packages for GNSS data post-processing that are freely available to the academic community. There are over 780 CORS in the GOM region as of 2014. Approximately, 350 of those CORS have a history longer than 5 years. The long-term accumulation of continuous GNSS observations makes it possible to establish a regional reference frame for precisely and coherently delineating minor ground deformations over time and space. This study established a stable Gulf of Mexico reference frame (SGOMRF14) using GNSS data up to the end of 2014. The GIPSY-OASIS software package (V6.3) developed and maintained by the Jet Propulsion Laboratory was used to calculate daily positions in this study. GIPSY-OASIS employs the single-receiver phase ambiguity fixed precise point positioning method, which resulted in 2–3 mm horizontal and 7–8 mm vertical repeatability within the GOM region. Applications of the GOM GNSS geodetic infrastructure in monitoring plate motions, land subsidence and sea-level rise are illustrated in this paper.

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7. Visualising changing tenure relationships: the talking titler methodology, data mining and social network analysis
M. Barry & K. Asiedu

Networks of social relationships and how they evolve in relation to land interests are a fundamental attribute of land tenure systems. Individuals may be members of complex, multi-layered, changing and conflicting social networks at any particular time in changing situations. The Talking Titler relational data model (TTM), data mining and social network analysis (SNA) were used to visualise and explore rapidly changing land interests using an urbanizing customary society as the illustrative context. Land tenure relationships may change rapidly in situations where both external forces and internal agents foment conflict and social change in local politics, and elites may abuse their power to grab land. Peri-urban customary systems evolve in response to urbanization, titling programmes and land sales that put pressure on traditional customary norms. Social network analysis can facilitate visualizing complex patterns of relationships between people and how they relate to land. It may also identify new, previous, unknown and changing relationships and structures on the ground. There are practical challenges to applying the tools, but the methodology and data mining and network analysis techniques show promise as an addition to the set of tools that may be used to improve tenure security and as a scenario analysis tool.

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