Updating of digital topographic maps in the new national spatial coordinate system: case Fergana valley in Uzbekistan

The classical geodetic coordinate system (CS42) in Uzbekistan uses the Krasovsky ellipsoid. The implementation of new information technologies, such as the Global Navigation Satellite System, became the basis for the development of a new national open geocentric coordinate system. This paper describes the development of a distortion grid for transforming horizontal spatial data from the local geodetic datum CS42 to a geocentric datum WGS84 for 1:100000 scale maps of the Fergana Valley in Uzbekistan. A first version of the distortion grid file has been created for transforming between CS42 and WGS84 for the whole territory of the country. The significant influence of the longitudinal drift of the region has been confirmed. The grid was used to transform topographic maps at a scale of 1:100000 for the Fergana Valley. Changing the map datum has shifted the grid of coordinate systems by 70 m in the East and 7 m in the North.

GNSS network of Uzbekistan: achievements, prospects and challenges

<p>In 2005, a governmental program for the creation of a geodetic network (SGN) based on GNSS measurements started in the Republic of Uzbekistan. Its main goal is to provide a modern, reliable and accurate geocentric coordinate system for land management, construction, environmental protection and the creation of a spatial database for various sectors of the economy. The SGN established in the country based on the availability of infrastructure and geographical needs and therefore, it does not cover the entire country. SGN consists three levels: reference geodetic points (RGP), high precision satellite geodetic network (SGN-0) points and first class satellite geodetic network (SGN-1) points. Since 2018, a network of 50 Continuously Operating Reference Stations (CORS) has also been developing. The installation of more than 200 GNSS stations in the period from 2005 to 2020 allows the country's scientific community to solve a number of practical geodetic problems. Among them implementation global ITRS system into local area for transition to new national geocentric coordinate system, quasi-geoid determination based on high degree Global Geopotential Models (such as EGM2008, EIGEN-6C4, GECO) and local geodynamic research for stress field modeling.</p>

ANALYSIS OF COMMON QUALITY PROBLEMS IN COORDINATE TRANSFORMATION BETWEEN REFERENCE COORDINATE SYSTEM AND GEOCENTRIC COORDINATE SYSTEM

<p><strong>Abstract.</strong> In the working of the existing reference coordinate system transformed into the coordinate system of the geocentric coordinate system, many experts and scholars have in-depth research on the transformation methods such as geodetic control point results (including GNSS base station coordinates, GNSS control point coordinates, triangle point coordinates), basic geographic information data results (including DLG, DOM, DEM, DRG, DSM, etc.) and other spatial information data. On the basis of these studies, many provinces and cities have completed the coordinate system transformation of surveying and mapping results in China. This paper expounds the method of transforming the existing reference coordinate system into the geocentric coordinate system, summarizes and sorts out the common quality problems in the process of different data and different methods, and analyses the causes of the problems and the impact on the transforming results. Based on the above work, The paper provides reference and suggestions for the transforming work, which is aimed to improve the transformation quality in the future.</p>

External thermal modeling satellite platform «Synergy»

In order to conduct thermal research of the satellite platform «Synergy», a mathematical model has been developed for calculating external thermal loads for spacecraft of the CubeSat form factor, operating in various orientation modes in near-Earth circular orbits. When modeling thermal conditions, heat fluxes from the Sun, the earth's flux and atmospheric effects are taken into account. A feature of the model is the transition to a moving geocentric coordinate system for determining the density of heat fluxes of direct and reflected solar radiation. The study of thermal conditions in the process of orbital motion is carried out and the parameters of the position of the orbital plane and the parameters of the Sun are determined at which the maximum and minimum average integral thermal loads are achieved during the orbital period. In these orbits, the motion of the satellite platform was simulated in three typical orientation modes and the density values of the absorbed heat fluxes by its external elements were determined. Four options for the design of the housing are being investigated. The data obtained during the simulation were used for the initial stationary calculation of the temperature field of the satellite platform in the ANSYS software package. The most interesting cases from the point of view of the thermal regime for further thermal research have been identified.

Geocentric Coordinate Systems and Actual Problems of Modernization of the State Geodetic Network

The article describes the state of the geocentric coordinate system of the Russian Federation. Current problems of the geodetic coordinate system are described, and a method for solving this problem is proposed.

Chinese Geodetic Coordinate System 2000 and its Comparison with WGS84

It is a general trend to adopt the geocentric coordinate system as a geodetic datum for the international measurement community. The definition and realization of Chinese geocentric three-dimensional coordinate system (CGCS2000) which has been employed since July 1st, 2008 were introduced in detail. The defining parameters and derived constants of the reference ellipsoid used were given. The comparison between CGCS2000 and WGS84 was carried out. The differences of geodetic coordinates of a point between the two coordinate systems, normal gravity and vertical gradient of normal gravity on the two ellipsoids caused by the change of the flattening of the ellipsoid were analyzed. The results show that these differences could be neglected in view of present measurement accuracies.

Study on the Trajectory Simulation of the Ballistic Missile

Based on the geocentric coordinate system, the object coordinate system as well as the theory of elliptic trajectory, it makes research and analysis of the ballistic-parameter-based trajectory generation method of the ballistic missile and, meanwhile, verifies the effectiveness and rationality of this method. It, under the assumed condition of elliptic trajectory, also researches the solution process of the ballistic parameters in the midcourse of the ballistic missile and, meanwhile, makes the simulation verification on the midcourse trajectory of the ballistic missile according to the radar sights variation relation in the object coordinate system during the motion process.