Burak Akpınar

Multisensor Railway Track Geometry Surveying System

Linear variable differential transformers (LVDTs) and inclinometers are widely used in many industrial establishments, particularly in the metrology area. These sensors are used by many engineering disciplines because of their high-precision characteristics. In addition, Global Navigation Satellite System (GNSS) receivers and total stations are widely used in geodesy. Using GNSS receivers is very popular, particularly for navigational purposes. In this paper, a new railway track geometry surveying system, which is designed by integrating the LVDT, inclinometer, GNSS receiver, and total station, is introduced. This new surveying system is an alternative to classical geodetic measurement methods that are often used for controlling the railway track geometry. Track gauge, super-elevation, gradient, and track axis coordinates, which are railway geometrical parameters, can be instantly determined while making measurements by using the new surveying system.

Hydrographic data modeling methods for determining precise seafloor topography

Acoustic and light detection and ranging are the recent methods used in hydrographical surveying. Depth values depending on X and Y horizontal coordinates are measured in both methods. While processing the hydrographical data, all data with different density are interpolated and modeled for determining the seafloor model using different interpolation techniques. In this study, effects of different surface modeling methods are investigated. Data obtained from single-beam echo sounder (SBES) are modeled using inverse distance, kriging, local polynomial, minimum curvature, moving average, nearest-neighbor, and Delaunay interpolation methods. Interpolation results are compared with the multibeam echo sounder data which were collected on the same area for determining the accuracy of modeling methods. Depending on the maximum total vertical uncertainty values in hydrographic survey standards, the best results were determined by using the kriging method. The Delaunay, minimum curvature, and inverse distance methods can be used for modeling the SBES data in shallow waters.

ANALYSIS AND MANAGEMENT OF GNSS REFERENCE STATION DATA

E. Gulal i dr. Analiza i upravljanje GNSS podacima referentne postaje Tehnicki vjesnik 22, 2(2015), 407-414 407 ISSN 1330-3651 (Print), ISSN 1848-6339 (Online) DOI: 10.17559/TV-20140717125413

Online system for monitoring the safety of engineering structures

Original scientific paper Monitoring engineering structures is a very important issue for the safety of these structures. Maintaining the safety of engineering structures depends on determining the possible deformations to the structures and taking the necessary precautions in time. In this instance, monitoring the structures became a very important problem. In this study, a prototype of web-based online monitoring system design and implementation was carried out for monitoring the movements of Fatih Sultan Mehmet Bridge which was one of Istanbul’s suspended bridges. Raw observations taken by geodetic instruments can be filtered by different filtering techniques and can be analyzed by trend and FFT analysis methods. With the help of these techniques, overall monitoring of the structure was possible. Designed monitoring system can be used on different types of engineering structures such as skyscrapers and dams. With the help of this online monitoring system, project managers or any other officials, in the office, can see the observations in real time and can analyze the results while operators are working near the structure.

Wireless 3-axis accelerometer system for measurement of structural displacement

In this study, we present the design of a 3-axis acceleration measurement system that is capable of UTC (Coordinated Universal Time) time-stamping captured from a Global Positioning System (GPS) receiver module. With this achievement, the system is able to monitor and record the 3-axis vibrations with respect to an absolute time rather than the local sensor (and computer) time. Acquired 3-axis acceleration data and UTC are transferred via Bluetooth® protocol and developed software which enables monitoring and recording of UTC and acceleration data on a PC, respectively. For verification and synchronization quality test of acceleration data, shake-table tests were conducted for simulation of structural displacement and the calculated displacements were compared with a displacement sensor of a commercially available shake table system.

Current Tectonic Movements Monitoring in Aksehir-Sultandagi Fault Zone After the February 2002 (Mw: 6.2) Earthquake

Aksehir-Sultandagi Fault Zone (ASFZ) is one of the most important seismogenic zones located in the expansion region of Western Anatolia.

Determining the Coordinates of Control Points in Hydrographic Surveying by the Precise Point Positioning Method

After Global Navigation Satellite Systems (GNSS) were first used in the field of hydrography in 1980, developments in hydrographic surveying accelerated. Survey precision in hydrography has been improved for both horizontal and vertical positioning and seafloor acoustic measurement by means of these new developments. Differential Global Positioning System (DGPS), Real Time Kinematic (RTK) and Network RTK (NRTK) techniques are the satellite-based positioning techniques that are commonly used in shallow water surveys and shoreline measurements. In line with these developments, the newer Precise Point Positioning (PPP) has been introduced. Combining precise satellite positions and clocks with dual-frequency GNSS data, PPP can provide position solutions from the centimetre to decimetre level. In this study, the coordinates of control points were determined by using the Post-Process PPP (PP-PPP) technique. Seven test points, which are the points of the Continuously Operating Reference Station - Turkey (CORS-TR) network, are selected near the shorelines within Turkey. The 24-hour data was split from one to six hours by one hour periods. Automatic Point Positioning Service (APPS) was selected to process the data. The poisoning error of the test points were given and compared with International Hydrographic Organization (IHO) S44 hydrographic survey standards.