Uzbekistan's coordinate system transformation from CS42 to WGS84 using distortion grid model

Currently,a non-geocentric geodetic coordinate system introduced in 1942(CS42),based on the Krasovsky ellipsoid and the Baltic system of normal heights introduced in 1977,is used for geodetic works in the Republic of Uzbekistan.The development of the GNSS network proposes a task of transition to a new geocentric system based on the World Geodetic System 1984(WGS84)ellipsoid.Many software products adopt 3-or 7-parameter conversions,which can cause errors up to several meters and are not suitable for many applications.In this case,local transformations using a grid of differences between observation points with known coordinates in both datums would give the best accuracy.In this paper,we discuss various interpolation methods(Kriging,Minimum Curvature,Inverse Distance to a Power and Radial Basis Function)to solve the distortion modeling between CS42 and WGS84 systems for national datum improvement.The results show that the distortion models share a common tendency for all interpolation methods:the maximum horizontal displacements are concentrated along the West Tien Shan lineament,which is the boundary of the relief lowering.The discrepancies between the grid-based(calculated)and GPS-measured coordinates are evaluated.Statistical and spatial analysis has confirmed that for the co-ordinate transformation from CS42 to WGS84 and vice versa,grid-based transformation with Radial Basis Function interpolation has a high accuracy transformation.Analysis of the available data across the eastern part of the country shows that some positional distortions existed between the CS42 and WGS84 datums.For the best RBF method,the magnitude of these distortions is about 0.019-0.755 m with a standard deviation of 0.015 m.

The review and development of a modern GNSS network and datum in Uzbekistan

This study is focused on the discussion of a modern GNSS network and datum in Uzbekistan.Considering the significance difference(up to 200 m) in positions of the local ellipsoidal datum and the global datum,the precise transformation parameters between national geodetic datum CS-42,and the World Geodetic System 1984(WGS84) global datum used by the GPS is estimated.This study aims to evaluate the accuracy of the currently used transformation parameters from different sources in the region,and give preliminary recommendations for using these sets also.The differences between transformed,original and WGS-84 coordinates were calculated and evaluated.On the basis of this difference,different zones for determination of transformation parameters have been proposed.

The lineaments as one of the precursors of earthquakes: A case study of Tashkent geodynamical polygon in Uzbekistan

This work is to study earthquake precursors using lineament analysis of five MW3 earthquakes that occurred in 2018 on the territory of the Tashkent geodynamic polygon in Uzbekistan.The Landsat 8 satellite images were processed using the automated lineament detection method in the LEFA software.The processing steps included image preprocessing with graphic filters,edge detection using Canny’s algorithm,the definition of a vector of linear elements based on the probabilistic Hough transform and combining collinear linear elements into lineaments.The analysis of the cyclicity of precursors before and after earthquakes was based on the study of the distribution of the lineaments trend in the study area using rose diagrams and lineaments density maps.The results showed a change in the dynamics of the lineament structure.The statistical analysis of lineaments revealed that the number and orientation of lineaments changed significantly about 2-4 months before an earthquake,and after 2-3 months,the system gradually returned to its initial state.The rapid increase in lineaments density began almost 20 days before the event,reaching a maximum about 4 days before the earthquake,and its decrease began16 days after the earthquake.The main trends observed in the lineament map showed dominant trends in NS,EW,and the subdominant directions were in NW-SE,NE-SW,which coincided with main directions of the faults.