Omer Yildirim

Determination of 2011 Van/Turkey earthquake (M = 7.2) effects from measurements of CORS-TR network

Turkey is a country that has active fault lines and is prone to earthquake. The positional variations resulted from the Van earthquake (a magnitude of M = 7.2) on 23 October 2011 and were calculated by using data from CORS-TR (Continuously Operating Reference Station network) stations. The GPS data from the CORS-TR stations effected from the earthquake were evaluated by the BERNESE 5.0 software. For calculating the positional displacements in the CORS-TR stations after the earthquake that occurred in Van, the measurements from 16 International GNSS Service (IGS) stations around Turkey, where their coordinates and velocity vectors were considered to be constant at the ITRF2005 datum. The greatest variation was measured from the Muradiye station, which is the closest point to the epicentre of the earthquake. The variation in this station was −42.7 mm in the vertical direction, −60.3 mm in the northern direction and −18.7 mm in the eastern direction.

Regularized estimation of Euler pole parameters

Euler vectors provide a unified framework to quantify the relative or absolute motions of tectonic plates through various geodetic and geophysical observations. With the advent of space geodesy, Euler parameters of several relatively small plates have been determined through the velocities derived from the space geodesy observations. However, the available data are usually insufficient in number and quality to estimate both the Euler vector components and the Euler pole parameters reliably. Since Euler vectors are defined globally in an Earth-centered Cartesian frame, estimation with the limited geographic coverage of the local/regional geodetic networks usually results in highly correlated vector components. In the case of estimating the Euler pole parameters directly, the situation is even worse, and the position of the Euler pole is nearly collinear with the magnitude of the rotation rate. In this study, a new method, which consists of an analytical derivation of the covariance matrix of the Euler vector in an ideal network configuration, is introduced and a regularized estimation method specifically tailored for estimating the Euler vector is presented. The results show that the proposed method outperforms the least squares estimation in terms of the mean squared error.

COMPARISON OF REGIONAL AND GLOBAL TEC VALUES: TURKEY MODEL

The ionosphere is a layer of atmosphere 60 km to 1,100 km above the earth and is composed of solar rays and ionized gases. The ionosphere is an important layer affecting Global Navigation Satellite System (GNSS) measures. The quality of GNSS measures is directly related to the changes in the ionosphere. For this reason, monitoring changes in the ionosphere is quite important. One of the important parameters expressing the characteristic of the ionosphere is the Total Electron Content (TEC), which is a function of electron density exhibiting transformation with solar radiation. In this study, 68 stations including 56 TUSAGA-Active (CORS-TR) stations and also IGS stations were taken for evaluation. Bernese v5.2 GNSS software developed by Bern University of Switzerland was employed at the evaluation stage. From 2009 until 2015, TEC values were calculated at two hourly intervals, one day for each month. In the study, where a Single Layer Model was used, TEC values obtained from GNSS measurements have been compared with the TEC (IRI-2012 TEC) values obtained from the global ionosphere map (GIM-TEC) and the international ionosphere reference model programme published by the Centre for Orbit Determination in Europe (CODE), the European Space Agency (ESA), and the Jet Propulsion Laboratory (JPL).

UAV Based Agricultural Planning and Landslide Monitoring

The use of Unmanned Aerial Vehicle (UAV) tools has become widespread in map production, land surveying, landslide, erosion monitoring, monitoring of agricultural activities, aerial crop surveying, forest fire detection and monitoring operations. In this study, GEO 2 UAV manufactured by TEKNOMER equipped with SONY A6000 camera has been used. The flight plan have been performed with 100 m altitude, with 80% longitudinal and 60% side overlapping. Ground Control Points (GCPs) have been observed with Topcon and Trimble GNSS geodetic receivers. Recorded GNSS signals have been processed with LGO V.8.4 software to get sensitive location information. 985 photos have been taken for the 344 hectares the agricultural area. 291 photos have been taken for 50 hectares the landslide area. All photos were processed by PIX4D software. For the agricultural area, 25 GCPs and for the landslide area, 8 GCPs have been included in the evaluation. 3D images were produced with pixel matching algorithms. As a result, the RMS evaluation was obtained as ±0.054 m for the agricultural area and as ±0.018 m for the landslide area. UAV images have indisputable contributions to the management of catastrophes such as landslides and earthquakes, and it is impossible to make terrestrial measurements in areas where disaster impact continues.

Determining regional ionospheric model and comparing with global models

IZVLEČEK KLJUČNE BESEDE

Repeatable of Network RTK Measurement

Anahtar kelimeler GNSS; Klasik RTK; Ag RTK; Hizli statik yontem Ozet Gunumuzde nokta konumlarinin GPS/GNSS(Global Positioning System/Global Navigation Satellite Systems) ile gercek zamanli belirlenmesi genel olarak Klasik RTK(Real Time Kinematic) ya da Ag RTK(CORS: Continuously Operating Reference Stations) ile yapilmaktadir. CORS agini kuran ulkelerde ise Ag RTK yontemi tercih edilmektedir. Bu calismada Ag RTK olculerinin tekrarlanabilirligi test edilmistir. Olcmeler Selcuk Universitesi Kampus alaninda bulunan TUTGA(Turkiye Ulusal Temel GPS Agi) SLCK noktasinda farkli duzeltme teknikleri kullanilarak gerceklestirilmistir. Secilen duzeltme tekniklerinde olcmeler ucer gun sure ile 10-14 saatleri arasinda yapilmis, elde edilen koordinatlarin gunluk degisimi ve bilinen koordinatlara yaklasimi arastirilmistir. Yapilan degerlendirmelerde; gun icindeki koordinat farklarinin secilen duzeltme teknigine gore farklilik gosterdigi, yukseklik yonundeki farklarin x ve y yonundeki farklarin yaklasik 2 kati oldugu, gercek degere en iyi yaklasimi VRS tekniginin gosterdigi, butun duzeltme tekniklerinde elde edilen koordinatlarin bilinen koordinatlarla istatistiki anlamda uyusumlu oldugu sonucuna varilmistir.