Ionospheric TEC from the Turkish Permanent GNSS Network (TPGN) and comparison with ARMA and IRI models

Abstract: The present study investigates the ionospheric Total Electron Content (TEC) variations in the lower mid-latitude Turkish region from the Turkish permanent GNSS network (TPGN) and International GNSS Services (IGS) observations during the year 2016. The corresponding vertical TEC (VTEC) predicted by Auto Regressive Moving Average (ARMA) and International Reference Ionosphere 2016 (IRI-2016) models are evaluated to realize their effectiveness over the region. The spatial, diurnal and seasonal behavior of VTEC and the relative VTEC variations are modeled with Ordinary Least Square Estimator (OLSE). The spatial behavior of modeled result during March equinox and June solstice indicates an inverse relationship of VTEC with the longitude across the region. On the other hand, the VTEC variation during September equinox and December solstice including March equinox and June solstice are decreasing with increase in latitude. The GNSS observed and modeled diurnal variation of the VTEC show that the VTEC slowly increases with dawn, attains a broader duration of peak around 09.00 to 12.00 UT, and thereafter decreases gradually reaching minimum around 21.00 UT..

Numerical Simulation of Crustal Strain in Turkey from Continuous GNSS Measurements in the Interval 2009–2017

The present study investigates the crustal strain in Turkey by using data from the Turkish permanent GNSS network (TPGN) and international GNSS services (IGS) observations for a period of 9 years, 2009 t0 2017. The positional variation of GNSS sites is studied to understand the coordinate reliability, interseismic and coseismic effects and linear velocities as well as three dimensional principal strains across the country. The study of coordinate reliability shows that the horizontal and vertical residuals in 2013 and 2015 are of the order of 100 mm per coordinate or higher than those of 2009 and 2011 and 10 times higher than those of 2017. The changes in baseline length relative to an arbitrary zero-o_set for the selected period shows that the most of the sites have displacement in the interval −10 to 10 mm but some sites have larger variations. These displacements are mostly related to motion of the Turkish tectonic plate, regional crustal deformation and small amounts of errors inGNSS positioning. The most GNSS site velocities located all over Turkey give significant information for the study. The GNSS data shows that the Anatolian plate relative to the Eurasia is moving in a western direction in the central part of Turkey and starts to move in a south-westerly direction in the west part of the country. The westward motion of Anatolia increases gradually from 20 mm/yr in central Anatolia to 30 mm/yr in south-west Turkey. The numerical simulation of the crustal strain in the Aegean region shows a maximum 1.0446×10−6 compressional principal strain rate while the second principal strain rate is zero. The strain in Central Anatolia is evidently dominated by extensional deformations and the principal strain rate reaches to 0.9589×10−6 with maximum extension. The Marmara Region network is subject to an extensional principal strain (0.6608×10−6) which is also revealed in the Mediterranean Region with a 0.5682×10−6 extension. The present analysis of GNSS data over the region may complement towards the understanding of the stability of regional tectonics and long term aseismic strain inside the country

Coordinate transformation parameters in Nepal by using neural network and SVD methods

The present study computes B-W extension model (extended Bursa-Wolf model) coordinate transformation parameters from World Geodetic System 1984 (WGS-84) to the Everest datum namely Everest (1830) and Everest (1956) using records of coordinate measurements from Global Positioning System (GPS) observable across Nepal region. Synthetic or modeled coordinates were determined by using the Artificial Neural Network (ANN) and Singular Value Decomposition (SVD) methods. We studied 9-transformation parameters with the help of the ANN technique and validated the outcomes with the SVD method. The comparative analysis of the ANN, as well as SVD methods, was done with the observed output following one way ANOVA test. The analysis showed that the null hypothesis for both datums were acceptable and suggesting all models statistically significantly equivalent to each other. The outcomes from this study would complement a relatively better understanding of the techniques for coordinate transformation and precise coordinate assignment while assimilating data sets from different resources