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In order to study and expand the application of BeiDou Navigation System in railway engineering survey, the technical advantages of BDS system are used to solve the problem of railway surveying and positioning in mountain areas. Based on a railway in mountain areas, this paper has established a belt-shaped BeiDou continuous operation reference station system (hereinafter referred to as "BeiDou CORS System") and a high-precision location service cloud platform. The domestic multisatellite and multi-frequency survey receiver is used to collect the data of control points. The survey accuracy of RTK observation data of BDS, GPS and GNSS hybrid ephemeris network based on BeiDou CORS System and RTK observation data in the form of traditional base stations are compared respectively. The results show that: (1) The positioning function of network RTK based on railway banded BeiDou high-precision location service cloud platform is stable and reliable; (2) The network RTK measurement method based on the Beidou CORS system only needs to perform elevation surface fitting, and the accuracy of the results collected in 3s can meet the accuracy requirements of the network RTK center line survey, section survey, construction stakeout, and image control survey in the railway survey code. The same type of equipment and the same precision observation method should be used as much as possible to ensure the repeated survey accuracy, and the survey accuracy can also be improved by increasing the observation time and using the existing elevation control points for elevation correction in local areas; (3) The internal coincidence accuracy tolerance of plane and elevation of network RTK survey based on BeiDou CORS System can be set to 1.7 cm and 2 cm, and the outer coincidence accuracy can be set to 2.2 cm and 5 cm. [ABSTRACT FROM AUTHOR]

Unmanned Aerial Vehicles (UAV) have widely been served as a new technology in agricultural aviation plant protection and pest control in China. However, it is highly demanded to improve the accuracy of UAV spraying pesticides and operational efficiency. In this study, a Variable Rate Application (VRA) of a centrifugal spraying system was designed for precise placement and timing of pesticide application in specific field conditions using the network Real-Time Kinematic (RTK) technology. STM32F103 single-chip microcomputer was used for the core controller. A serial port of controller was selected to obtain the global position system (GPS) information. A network modular Data Terminal Unit (DTU) was connected to realize the network RTK technology via the serial port of the controller. The control voltage was used to tailor the speeds of the centrifugal nozzle motor and peristaltic pump. A Pulse Width Modulation (PWM) was used to control the output voltage from the core controller to the armature of motors in this system. The speed of the centrifugal nozzle motor determined the output droplet size, while the speed of peristaltic pump determined the flow rate and amount of spray fog. The agricultural dataset before the system working was acquired using the airborne multispectral camera, ground object spectrometer, and handheld GPS. A prescription chart was also constructed using ArcGIS software. In the system working, the GPS modular was used to capture the location longitude and latitude data for the system to read and analyze. The system was always real-time searching the UAV geographical position during the spraying pesticides process using the GPS data, and then matching the position using the orthogonal grid. Meanwhile, the system was used to real-time tailor the changes in the duty cycle of output PWM, after matching the decision of the prescription map. The speeds of the centrifugal nozzle motor and the peristaltic pump were then to control the particle size and application amount of the UAV. The operation data was finally uploaded to the monitoring platform for real-time display and storage. Several spraying experiments were carried out in the research base of South China Agricultural University in Zengcheng City, Guangdong Province of China. The airborne spraying device was carried on the MG-1p plant protection UAV using a developed DJI Drone. The sampling points of droplets were set to match the planting density of crops, where the water-sensitive paper was used to collect the droplet data. After UAV operation, the water sensitive paper was collected into a plastic bag for later use. An hp4678 scanner was selected to map the collected water-sensitive paper after the experiment. A DepositScan software was utilized to analyze the water-sensitive paper in each sampling area after image acquisition. A detailed dataset was obtained, including the deposition amount, coverage density, and particle size of droplets. The data demonstrated that the accuracy of the device was within 0.6 m at the operating speed of 2 m/s. The application effect was finally stabilized within 2.2 m in the case of continuous operation. Particle size varied smoothly in the boundary area of prescription, as the rotating speed of the centrifugal nozzle increased. The findings can provide a sound basis for the improvement of variable application technology of plant protection UAV in precise agriculture. [ABSTRACT FROM AUTHOR]