This article focuses on a specially designed steel beam testing apparatus to determine the dynamics of the structure using data obtained from different sensor systems. The analysis of these different sensor systems is performed by processing data recorded by the Global Navigation Satellite System (GNSS), vision based measurement (video camera), and accelerometer surveys. To perform this analysis, the accelerometer and GNSS receiver are installed at the steel beam’s mid-span position. The high-contrast artificial target attached to the accelerometer is recorded by a video camera to monitor the structural dynamics. Steel beam experiments show that it is compatible with the accelerometer, which is predicted as a reference sensor in detecting motion with an amplitude of 10 mm and above in the vertical direction with GNSS and determining the structural frequency by spectral analysis. On the other hand, we concluded that the video camera can be used to determine the structural dynamics in SHM because its results were compatible with the reference data even if the amplitude was too small.

In urban environments, GNSS positioning is challenging due to signal blockage and multipath effects of surrounding buildings. This study evaluates the compatibility of CORS-VRS, PPK and static GNSS methods with total station measurements to investigate their accuracy in urban conditions. For this purpose, measurements were conducted in Esenler, Istanbul on 30 September 2020. Three measurement points (P1, P2 and P3) with varying levels of obstruction were selected. The results demonstrate that static GNSS measurements (with horizontal and vertical components below 5 mm and 11 mm, respectively) are the method with the highest positional accuracy. Conversely, PPK measurements exhibited larger deviations (0.857 m (X), 0.356 m (Y), and 0.780 m (Z) in P1, 0.302 m (X), 0.215 m (Y), and 0.255 m (Z) in P1, and 0.516 m (X), 0.284 m (Y), and 0.374 m (Z) in P3. Conversely, CORS-VRS measurements exhibited deviations ranging from 13 cm to 34 cm at baseline distances when compared to total station results. The findings demonstrate that while CORS-VRS and PPK can achieve sub-decimeter accuracy, they are significantly affected by multipath and signal blockages in dense urban environments. Thus, GNSS-based positioning in urban settings should be supplemented with total station surveys when high precision (1-2 cm) is required.

Çalışmanın amacı, Burdur Gölü'nün su yüzey alanı üzerindeki mekânsal değişimleri analiz etmek ve Burdur Gölü Havzası'ndaki uzun yıllık iklim kayıtlarındaki eğilimleri inceleyerek göl yüzey alanının gelecekteki durumu hakkında tahminler yapmaktır. Bu doğrultuda, çalışma alanı için Landsat 4-5 ve Landsat 8 uydu görüntüleri kullanılarak analizler gerçekleştirilmiştir. Bu görüntülerin sınıflandırılması, Modifiye Normalleştirilmiş Fark Su İndeksi (mNDWI), Normalleştirilmiş Fark Su İndeksi (NDWI) ve Su İndeksi 2015 (WI2015) su indisleri kullanılarak yapılmıştır ve 1985-2021 yılları arasında her yıl için göl yüzey alanı verileri toplanmıştır. Çalışmanın sonuçlarına göre, Burdur Gölü'nün su alanı 1985 yılı ile 2021 yılı arasında büyük oranda (81.7-92.3 km²) azalmıştır. Yapılan doğrusal regresyon analizlerine dayanarak, gölün 2070-2080 arasında kuruyacağı tahmin edilmektedir. WI2015 yöntemi, OMH (7.0554) ve GOMH (4.1711) gibi düşük hata değerleri ile 0.9923'lük yüksek korelasyon katsayısı ile en başarılı yöntem olarak değerlendirilebilir.

No studies have been conducted on the spatial changes related to the Hatay-Defne earthquake (20 February 2023) up to now. The reason for this situation is that the requested data cannot be accessed as a result of the power and internet interruptions caused by the earthquake. The southern Turkish city of Hatay had a 6.3 magnitude earthquake at 20:04 on February 20, 2023. Three minutes later, a 5.8 magnitude aftershock occurred, and 90 more aftershocks followed. These earthquakes, which were felt across the area, caused individuals who survived the horrific quakes on February 6, 2023, to experience new levels of dread. In the district of Hatay-Defne, the epicenter began. In its first assessment, the United States Geological Survey gave the earthquake a magnitude of 6.3 at a depth of 16 kilometers. In this study, firstly, GNSS data belonging to ARST station in 30 seconds recording interval were downloaded into CSRS-PPP. GNSS data was processed as static and then was processed as epoch to epoch by using kinematic method. The coordinate differences between the obtained coordinates by using the kinematic processing and the obtained coordinates by using the static processing were computed. According to the obtained results, a horizontal movement of approximately 8.30 cm in the south-west direction was observed at the ARST station, which is the closest to the earthquake center.

Refraction is one of the most important factors affecting the accuracy of optical and electromagnetic measurement systems. In this study, the effect of refraction on measurement accuracy was investigated by processing video camera images obtained under different distances, temperatures, and object height conditions. Video camera recordings directed at a fixed target were processed using the Template Matching method in MATLAB. The normalized cross correlation (NCC) algorithm was used to prevent the effects of brightness or contrast differences and to ensure a more reliable comparison. A time series of target position changes (caused by refraction) was obtained, and the results were interpreted using statistical measures such as standard deviation (σ) and the F-test. The findings showed that the σ increased as distance and temperature increased, while the deviation decreased as the target height increased. Furthermore, the deviations of the horizontal component were found to be higher than those of the vertical component. For the first measurement, the deviations varied between ±0.3 and ±4.50 mm, depending on temperature and distance. In the second measurement, the deviation increased to ±6.8 mm when the measured object was 0.50 m above the ground, but decreased to ±2.6 mm at a height of 2.50 m. The deviation values obtained in the current study are not a problem for applications where a few centimeters of precision are sufficient in rough construction work. However, in applications requiring high precision, such as industrial measurements and deformation monitoring, refraction effects must be considered. The pressure factor was not investigated in this study, and future studies are recommended to evaluate the contribution of each parameter to refraction separately.