Cevat Inal

Bio: Cevat Inal is an academic researcher from Selçuk University. The author has contributed to research in topics: GNSS applications & Global Positioning System. The author has an hindex of 7, co-authored 38 publications receiving 157 citations.

Preliminary evaluation of precise inclination sensor and GPS for monitoring full-scale dynamic response of a tall reinforced concrete building

Abstract: It is necessary to use dierent sensors in an integrated manner - GPS, accelerometer, inclina- tion sensor and so on - in order to monitor and identify static, quasi-static and resonant response of tall buildings subjected to wind loading. There are some dierences among these sensors with respect to data sampling rate, data quality, and their mea- surement accuracy. Therefore, using dierent sen- sors together for a monitoring project is important because of the complementary nature of each sen- sor. In this study, the behaviour of a tall reinforced concrete building (30 stories high) under wind load has been monitored using GPS and inclination sen- sors. This paper assesses the dynamic measurement quality and reliability of inclinometers for building monitoring applications, and discusses the strengths and weaknesses of GPS vis-a-vis the use of inclina- tion sensors for monitoring the dynamic response of tall buildings under wind load. Data collected by these sensors have been analysed in the time and frequency domains. It was found that GPS observa- tions were distorted by multipath caused by a re- flecting surface on top of the building. From the analyses in the frequency domain, the 1 st mode nat- ural frequencies of the building determined from both sensors agree very well with each other. The discrepancy of this measured 1 st mode natural fre- quency compared to that derived from FEM (Finite Element Model) prediction is 7%.

Comparing GLONASS-only with GPS-only and hybrid positioning in various length of baselines

Abstract: Nowadays, GPS is the best positioning system with its constellation, but number of GLONASS satellites increased to the required number, with launched new ones, for positioning. With recent revitalization of GLONASS, a great number of high precision GLONASS and GPS/GLONASS receivers have been produced. In this paper, baselines of two networks have been analyzed in order to assess the usability of GLONASS on global positioning. In both networks, repeatabilities of results were investigated by using GPS, GLONASS and GPS/GLONASS data. Results revealed that repeatabilities of all baselines by using GLONASS observations are not consistent when compared to the GPS and GPS/GLONASS.

Use of the particle swarm optimization algorithm for second order design of levelling networks

Abstract: Abstract The weight problem in geodetic networks can be dealt with as an optimization procedure. This classic problem of geodetic network optimization is also known as second-order design. The basic principles of geodetic network optimization are reviewed. Then the particle swarm optimization (PSO) algorithm is applied to a geodetic levelling network in order to solve the second-order design problem. PSO, which is an iterative-stochastic search algorithm in swarm intelligence, emulates the collective behaviour of bird flocking, fish schooling or bee swarming, to converge probabilistically to the global optimum. Furthermore, it is a powerful method because it is easy to implement and computationally efficient. Second-order design of a geodetic levelling network using PSO yields a practically realizable solution. It is also suitable for non-linear matrix functions that are very often encountered in geodetic network optimization. The fundamentals of the method and a numeric example are given.

L 1 Norm Minimization in GPS Networks

Abstract: The least squares method is a statistical tool for the estimation of unknown parameters. All the results which are derived from the method of least squares are deteriorated when outliers are present in the observation data. Therefore, outliers have to be detected and eliminated by using statistical tests or robust methods. For this purpose, L 1 norm minimization, which is a robust method, can be used in geodetic networks. In this paper, the formulation of L 1 norm minimization for correlated observations is presented. The method is applied to a simulated GPS network. The performances of the least squares method and L 1 norm minimization are compared in the cases of observations with or without outliers. Our example shows that L 1 norm minimization is a more successful method than the least squares method for outlier detection and the obtained coordinates are more reasonable and reliable than those from the least squares when some observations are burdened with blunders.

Analysis of Displacement Response of the Ermenek Dam Monitored by an Integrated Geodetic and Pendulum System

Abstract: This paper studies the structural behavior of the Ermenek arch dam, the second highest dam in Turkey. The investigated period covers the stage of the last-quarter part of first filling (1 and 1/2 year) and the begging of its operational lifetime (1 year). Displacement responses of the dam to temperature load and water load are assessed in detail based on both geodetic and pendulum monitoring records. In addition, the present study explores the possibility and advantage of integrating pendulum-measured signals with geodetic-measured signals for the dam deformation monitoring. The analysis results reveal that pendulum-derived displacements at four gallery levels, along the vertical cross section of the dam, which exhibit periodicity and linear trend with different slope due to seasonal temperature oscillation and linearly increased reservoir level, respectively. Comparative evaluation of the results shows that there is very good agreement between geodetic-derived displacement in radial direction at the middle of the crest and corresponding pendulum-derived displacement.

Recent research and applications of GPS-based monitoring technology for high-rise structures

Abstract: SUMMARY Monitoring the response of structures, especially tall buildings, under severe loading conditions is an important requirement for the validation of their design and construction, as well as being a maintenance concern. This paper presents a review of current research and development activities (since 1995) in the field of high-rise structure health monitoring using the Global Positioning System (GPS). The GPS monitoring technology and its accurate assessment method are firstly briefly described. Then, the progresses on monitoring the displacement of the high-rise structure caused by the ambient effects including wind, thermal variation, and earthquake-induced responses are discussed in details. Following that, the states of the art of augmenting the GPS monitoring technology are reviewed. Finally, existing problems and promising research efforts in the GPS-based health monitoring are given. Copyright © 2012 John Wiley & Sons, Ltd.

Three-Dimensional Laser Scanning for Geometry Documentation and Construction Management of Highway Tunnels during Excavation

Abstract: Driven by progress in sensor technology, computer software and data processing capabilities, terrestrial laser scanning has recently proved a revolutionary technique for high accuracy, 3D mapping and documentation of physical scenarios and man-made structures. Particularly, this is of great importance in the underground space and tunnel construction environment as surveying engineering operations have a great impact on both technical and economic aspects of a project. This paper discusses the use and explores the potential of laser scanning technology to accurately track excavation and construction activities of highway tunnels. It provides a detailed overview of the static laser scanning method, its principles of operation and applications for tunnel construction operations. Also, it discusses the planning, execution, data processing and analysis phases of laser scanning activities, with emphasis given on geo-referencing, mesh model generation and cross-section extraction. Specific case studies are considered based on two construction sites in Greece. Particularly, the potential of the method is examined for checking the tunnel profile, producing volume computations and validating the smoothness/thickness of shotcrete layers at an excavation stage and during the completion of excavation support and primary lining. An additional example of the use of the method in the geometric documentation of the concrete lining formwork is examined and comparisons against dimensional tolerances are examined. Experimental comparisons and analyses of the laser scanning method against conventional surveying techniques are also considered.

Geodetic and Remote-Sensing Sensors for Dam Deformation Monitoring.

Abstract: In recent years, the measurement of dam displacements has benefited from a great improvement of existing technology, which has allowed a higher degree of automation. This has led to data collection with an improved temporal and spatial resolution. Robotic total stations and GNSS (Global Navigation Satellite System) techniques, often in an integrated manner, may provide efficient solutions for measuring 3D displacements on precise locations on the outer surfaces of dams. On the other hand, remote-sensing techniques, such as terrestrial laser scanning, ground-based SAR (synthetic aperture radar) and satellite differential interferometric SAR offer the chance to extend the observed region to a large portion of a structure and its surrounding areas, integrating the information that is usually provided in a limited number of in-situ control points. The design and implementation of integrated monitoring systems have been revealed as a strategic solution to analyze different situations in a spatial and temporal context. Research devoted to the optimization of data processing tools has evolved with the aim of improving the accuracy and reliability of the measured deformations. The analysis of the observed data for the interpretation and prediction of dam deformations under external loads has been largely investigated on the basis of purely statistical or deterministic methods. The latter may integrate observation from geodetic, remote-sensing and geotechnical/structural sensors with mechanical models of the dam structure. In this paper, a review of the available technologies for dam deformation monitoring is provided, including those sensors that are already applied in routinary operations and some experimental solutions. The aim was to support people who are working in this field to have a complete view of existing solutions, as well as to understand future directions and trends.

NLOS Correction/Exclusion for GNSS Measurement Using RAIM and City Building Models.

Abstract: Currently, global navigation satellite system (GNSS) receivers can provide accurate and reliable positioning service in open-field areas. However, their performance in the downtown areas of cities is still affected by the multipath and none-line-of-sight (NLOS) receptions. This paper proposes a new positioning method using 3D building models and the receiver autonomous integrity monitoring (RAIM) satellite selection method to achieve satisfactory positioning performance in urban area. The 3D building model uses a ray-tracing technique to simulate the line-of-sight (LOS) and NLOS signal travel distance, which is well-known as pseudorange, between the satellite and receiver. The proposed RAIM fault detection and exclusion (FDE) is able to compare the similarity between the raw pseudorange measurement and the simulated pseudorange. The measurement of the satellite will be excluded if the simulated and raw pseudoranges are inconsistent. Because of the assumption of the single reflection in the ray-tracing technique, an inconsistent case indicates it is a double or multiple reflected NLOS signal. According to the experimental results, the RAIM satellite selection technique can reduce by about 8.4% and 36.2% the positioning solutions with large errors (solutions estimated on the wrong side of the road) for the 3D building model method in the middle and deep urban canyon environment, respectively.