APPLICATION OF AERIAL PHOTOGRAPHY RESULTS, OBTAINED USING UAV DATA TO ESTIMATE THE RESIDUAL CAPACITY OF THE LANDFILL. PRACTICE OF THE REPUBLIC OF TATARSTAN

Assessment of the current residual capacity is a fundamentally important task, the solution of which is demonstrated on a landfill located in the Republic of Tatarstan. To solve the task, the modern methods of high-precision three-dimensional reconstruction were used based on the survey from an unmanned aircraft DJI Phantom 4, equipped with a global satellite navigation system (GNSS) receiver. As a result of combining the project data and data from field surveys into one coordinate system and elevations and reconstruction of designed underground and ground parts of landfill calculation, the difference of models and the residual capacity of the landfill becomes possible. Based on the materials considered as of July 2020, the residual capacity of the studied landfill is 41.2 % of the project capacity, which allows us to continue to operate this landfill. The proposed approach allows for rapid and high-quality active monitoring of the engineered facility. Photogrammetric processing of the results of low-altitude aerial photography makes it possible to obtain objective data on the current actual state of the landfills, to carry out competent and valid management of the landfill functioning. Significant, this will extend the landfill's lifetime, minimize the adverse effects on the environment and predict the yield to the project capacity much more accurately.

Evaluation of BDS-2 and BDS-3 Satellite Atomic Clock Products and Their Effects on Positioning

The BeiDou Navigation Satellite System (BDS) has completed third phase construction and currently provides global services, with a mixed constellation of BDS-2 and BDS-3. The newly launched BDS-3 satellites are equipped with rubidium and passive hydrogen maser (PHM) atomic clocks. The performance of atomic clocks is one of the cores of satellite navigation system, which will affect the performance of positioning, navigation and timing (PNT). In this paper, we systematically analyze the characteristics of BDS-2 and BDS-3 atomic clocks, based on more than one year of precise satellite clock products and broadcast ephemeris. Firstly, the results of overlapping Allan variations demonstrate that BDS-3 Rb and PHM clocks improve better in stability than BDS-2 Rb clock and are comparable to GPS IIF Rb and Galileo PHM clocks. Accordingly, the STDs of BDS-3 broadcast satellite clock are better than GPS and BDS-2, which are at the same level with that of Galileo. Secondly, the inter-system bias (ISB) between BDS-2 and BDS-3 is analyzed by satellite clock datum comparison and precise point positioning (PPP). Surprisingly, the discrepancy between BDS-2 and BDS-3 satellite clock datum has a great difference between products that could reach up to about 10 ns for WHU satellite clock products and broadcast ephemeris. Moreover, the ISBs between BDS-2 and BDS-3 satellite clocks are quite stable over one-year periods. Thirdly, due to the improved stability of BDS-3 atomic clock, the 68% positioning accuracy is better than 0.65 m at 10 min for BDS-3 PPP, based on broadcast ephemeris. Besides, the non-negligible bias between BDS-2 and BDS-3 will greatly affect the BDS precise data processing. The accuracy of positioning is greatly improved when considering the ISB.

Performance assessment of GNSS-based real-time navigation for the Sentinel-6 spacecraft

The feasibility of precise real-time orbit determination of low earth orbit satellites using onboard GNSS observations is assessed using six months of flight data from the Sentinel-6A mission. Based on offline processing of dual-constellation pseudorange and carrier phase measurements as well as broadcast ephemerides in a sequential filter with a reduced dynamic force model, navigation solutions with a representative position error of 10 cm (3D RMS) are achieved. The overall performance is largely enabled by the superior quality of the Galileo broadcast ephemerides, which exhibits a two- to three-times smaller signal-in-space-range error than GPS and allows for geodetic-grade GNSS real-time orbit determination without a need for external correction services. Compared to GPS-only processing, a roughly two-times better navigation accuracy is achieved in a Galileo-only or mixed GPS/Galileo processing. On the other hand, GPS tracking offers a useful complement and additional robustness in view of a still incomplete Galileo constellation. Furthermore, it provides improved autonomy of the navigation process through the availability of earth orientation parameters in the new civil navigation message of the L2C signal. Overall, GNSS-based onboard orbit determination can now reach a similar performance as the DORIS (Doppler Orbitography and Radiopositioning Integrated by Satellite) navigation system. It lends itself as a viable alternative for future remote sensing missions.

The Application of Satellite Navigation System in Deformation Monitoring

Global satellite navigation system has become one of the top technical means in the world. The use of satellite navigation in many fields, such as deformation measurement, civil navigation, search resources, geodetic survey, auxiliary precision engineering monitoring and so on, can play its high precision positioning, all-weather monitoring and other technical characteristics. At the same time, satellite navigation system is combined with modern information technology. Internet technology and so on, which realizes the automatic collection, transmission, processing and analysis of safety monitoring data, and the application efficiency is maximized. The present situation and application of satellite navigation system to monitor the deformation of high-rise buildings are studied in this paper. Nowadays, more and more high-rise buildings in the world have sprung up like bamboo shoots. Therefore, how to realize the satellite navigation system to carry on the all-weather, the high precision, the high efficiency monitoring to the high-rise building, carries on the diagnosis to the dangerous signal in time, timely carries on the forecast to the future possible danger and the timely stop loss, this has the very important realistic significance. By reading the literature, the paper expounds the concepts of satellite navigation system, satellite navigation system and Internet technology in detail. The paper mainly takes the high-rise building scaffold as the object of deformation monitoring, and expounds the advantages and reliability of GPS as high-tech for deformation monitoring of high-rise buildings. Finally, through experimental design, the recognition of GPS technology by comparative method reflects the inestimable position of satellite navigation technology.

Results of comparing astronomical-geodetic and navigational-geodetic methods of determining the components of the deflection of vertical

The authors present the results of comparing the components of deflection of vertical obtained through astronomical-geodetic and navigational-geodetic methods. The first one is based on comparing astronomical and geodetic coordinates of a location. This method has recently been widely implemented in a digital zenith camera systems using a small-sized digital telescope with an astronomical camera based on CCD or CMOS technologies, a high-precision inclinometer and satellite navigation system receiver. In this case, the combination of a telescope, an astronomical camera and an inclinometer enables determining the local direction of the plumb line, expressed by astronomical coordinates, from observations of stars at the zenith and using high-precision star catalogs. The navigational-geodetic method is based on comparing the results of the normal heights’ increments, defined through geometric leveling, and geodetic heights, computed with the relative method of satellite coordinate determinations. For each method, random and systematic components of the error and its confidence bounds were calculated; the absolute values of the deflection of vertical components at two geographically separated points were compared.

Research on BeiDou Satellite Positioning Algorithm Based on GPRS Technology

The BeiDou Satellite Navigation System of China can provide users with high precision, as well as all-weather and real-time positioning and navigation information. It can be widely used in many applications. However, new challenges appear with the expansion of the 5G communication system. To eradicate or weaken the influence of various errors in BeiDou positioning, a BeiDou satellite positioning algorithm based on GPRS technology is proposed. According to the principles of the BeiDou Satellite navigation system, the navigation and positioning data are obtained and useful information are extracted and sent to the communication network through the wireless module. The error is corrected by establishing a real-time kinematic (RTK) mathematical model, and the pseudorange is calculated by carrier phase to further eliminate the relativistic and multipath errors. Based on the results of error elimination, the BeiDou satellite positioning algorithm is improved and the positioning error is corrected. The experimental results show that the positioning accuracy and efficiency of the algorithm can meet the actual needs of real-time dynamic positioning systems.

Оцінка впливу похибок БІНС, яка побудована на MEMS-компонентах, на точність виведення ракети-носія надлегкого класу

The object of the article is the movement of an ultra-light class liquid-propellant launch vehicle in near-earth space. The subject of the research is the accuracy of launching a spacecraft by a launch vehicle. The article studies the effect of errors in the instruments of a strap-down inertial navigation system built with the use of MEMS sensors on the accuracy of launching a spacecraft into low-earth orbits with an altitude of up to 450 km for two modes of operation: with and without a satellite navigation system. Tasks: to identify the determining disturbing factors, to determine the influence of instrument errors on the trajectory tube, to determine the influence of instrument errors on the insertion accuracy, to perform a comparative analysis of the accuracy characteristics obtained for two modes of operation of the navigation system. Methods used analysis, synthesis, analogy, comparison, factor analysis, statistical modeling, statistical processing of modeling results. Results: a set of defining disturbing factors was revealed, the dependencies of the trajectory tubes on the altitude of the target orbit and flight time were obtained, the dependencies of the limiting deviations of the parameters of the spacecraft's orbit at the time of separation from the launch vehicle on the altitude of the target orbit were obtained. Conclusions. 1. It is shown that the determining perturbing factors are the zero drift of the gyroscope from launch to launch and the zero random drift of the gyroscope. 2. It was determined that the value of the trajectory tube monotonically expands on time and the height of the target orbit. Maximum deviations of the current position and absolute speed in the mode without using a satellite navigation system do not exceed 115 km and 140 m/s. For the mode using a satellite navigation system, these values do not exceed 140 m and 1.5 m/s. 3. It was revealed that the maximum deviations of the parameters of the spacecraft's orbit in the mode with the use of a satellite navigation system do not exceed 27 km in height, 1.8o in inclination, 4.5x10-4 in eccentricity, and 2.7o for the longitude of the ascending node. For the mode with a satellite navigation system - in height - 2.6 km, in inclination and longitude of the ascending node - 0.0003о, in eccentricity - 3.5x10-4. 4. Generally, the use of a satellite navigation system narrows the trajectory tube by twice, and the accuracy increases to four times, depending on the orbital parameters.

Determination of Wind Velocity Projections Taking into Account Measurements of Airspeed, Angles of Attack and Sideslip

The paper deals with the problem of estimating the projections of the wind velocity in flight. The proposed method allows to obtain estimates for three projections of wind speed in the normal Earth coordinate system using data from the satellite navigation system, as well as on-board aerometric measurements of airspeed, angles of attack and glide. The main idea underlying the method is that satellite measurements of three aircraft velocity projections relative to the Earth’s coordinate system are very accurate (errors usually do not exceed 0.2 m/s). This makes it possible to use satellite velocity measurements as a kind of reference, just as in practical metrology, in order to assess the errors of measurement tools, they are compared with a standard, that is, a significantly more accurate measurement tool. In order to implement this approach not in a metrological laboratory, but on board an aircraft, it is proposed to use the relationships known from the flight dynamics between the velocity projections in the Earth’s and associated coordinate systems, the angles of attack and glide, and the wind speed. Then, the three wind speed projections are assigned unknown parameters, which are found using parameter identification. It is assumed that the wind has a constant speed and direction in the processed section of the flight. The accuracy characteristics of the proposed algorithm were evaluated based on the data obtained on the flight simulator of a modern training aircraft. In the course of simulation, random measurement errors were generated at the levels corresponding to the flight experiment. The influence of the type of maneuvers on the accuracy the three wind speed projections estimates was also studied. It is shown that for all considered maneuvers, that is "barrel", "snake", stepwise inputs, the errors in estimating the horizontal components of wind speed generally do not exceed 5 %, the vertical component 10 %, with the duration of the sliding processing interval of 0.5 and 1.0 s, which allows not only to estimate the constant wind speed, but also to track its change.