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The article addresses applied aspects of using UAVs for monitoring winter wheat crops to assess the aftereffects of herbicides remaining on the culture of the predecessor. The issue has a local specificity related to inconsistencies of plant cultivation technologies and the inadequate study of the impact of modern plant protection products in domestic soil conditions. Restoring the crop yields is possible by timely identification of the causes of stress, but the time for decision-making is limited. This time can be reduced by state-of-the-art monitoring technologies applied at industrial scale. Laboratory studies using phyto cameras and spectral and spectral-spatial monitoring methods unambiguously testified to the stress caused by the aftereffect of herbicides, but did not allow to establish clear criteria. Therefore, we conducted field studies using UAV-mounted Slantrange complex and analyzing the DJI Matrice 200 to define the distribution of stress areas on the field. It was found that the reliability of monitoring data can increased computer data processing and computer training in the search for correlation links between the distribution of stress plants in the field and the implementation of technological operations, terrain topography, etc.

In the work on the basis of Arduino Mega and the W5100 controller, a web server is built for graphical display of remote client data obtained from temperature, pressure, humidity sensors. The server program is written in the Arduino IDE development environment. The Ethernet library for the W5100 has been updated, which for Arduino IDE ver. 1.0.3, 1.0.5-r2 caused the server to hang. The possibility of using the Dygraphs library for graphical visualization of data obtained with sensors is shown. Written scripts for drawing graphics for the projected web server. The data transfer rate from the Arduino web server for various network controllers ENC28J60, W5100, W5500 for the Arduino IDE programming environment and UIPEthernet, Ethernet, Ethernet2 libraries was analyzed. It is shown that with the lowest speed the data is transmitted by the web server with the ENC28J60 controller - 3.3Kb/s, with the largest controller W5500 - 23.4Kbytes/s. It is noted that these servers do not support multithreaded work. Therefore, they can not be used to create miniature universal web servers for processing multiple requests simultaneously. The server considered in the work can serve only one request from one remote client. The speed parameters of data transfer for the server on the ATmega328p microcontroller (Arduino UNO) with the network controller ENC28J60 are analyzed. The server program is implemented in C language in the AVR Studio programming environment. A high data transfer rate of 140Kb/s and a possibility of multithreading are noted. It is established that with simultaneous transmission of three files to different clients, the total transmission speed reaches 120-130Kb/s, and for each client 40-50Kb/s. It is shown that the use of such a server to solve the problem of graphical representation of data from sensors is difficult due to the complexity of transferring software to other microcontrollers and the limited library for working with a microSD card. The operation of the server developed here for three years has shown high reliability of its operation. The paper discusses the creation of a web server on the Arduino, which is a modernized HTTP basic authentication. The upgrade consists in the fact that for authorization a password is used from the list of passwords that is selected by the user on the basis of the key sent by the server. With each new login to the server, the previous password becomes invalid. Presents a practical example of a web server on Arduino Mega, Ethernet controllers: enc28j60 and w5500.

The paper considers the practical possibility of implementing the GPS Rescue mode for Betaflight ver.4.1.1 firmware in order to return the quadrocopter (UAV) to a point close to the take-off point coordinates. In this regard, an experimental prototype was built with a 250mm frame, but with which the OMNIBUSF4V3 flight controller was installed based on the STM32F405 microcontroller with a GPS receiver and a directional video camera for FTP flights. Betaflight OSD was configured to receive flight data in order to analyze the correct operation of the copter return algorithm. During flight tests, it was shown that the GPS Rescue mode allows you to return the UAV to the launch zone, subject to the settings presented in the work on the assembled quadcopter. When performing GPS Rescue mode, an important condition is the stable connection of the GPS receiver with the number of satellites not less than those installed when setting the firmware. If the number of satellites becomes less than the set, then within a few seconds the motors turn off and the copter falls. It is shown that for stable operation of the GPS Rescue mode, the copter during flight should use the stabilization mode (Angle) with the accelerometer turned on, perform a flight with small angles of inclination. It was found that the greater the angle of inclination of the coprera, the smaller the number of satellites the GPS receiver catches. Therefore, the GPS rescue mode is not advisable to use in Acro, 3D, Horizon flight modes when making flip-s. It has been practically established that the GPS Rescue mode is more appropriate to use in the event of a break in video communication with the heading camera (FPV flights) while maintaining communication with the control panel. In this case, the flight orientation is lost and the copter in automatic mode must be returned to the video communication zone. To do this, the control mode sets the stabilization mode (angle) and turns on the GPS Rescue mode. When establishing a video connection, determining the location, GPS Rescue mode is disabled from the remote control and the copter can continue flying via FPV. It was noticed that in case of communication failure with the control panel, GPS Rescue mode is automatically turned on. In this case, the copter returns to the starting point and in case of restoration of radio communication, the copter automatically restores control with the remote control. This moment must be monitored by the pilot, otherwise the copter may crash. Therefore, it is advisable in case of loss of communication to set the toggle switch on the control panel to GPS Rescue mode. Then, when the radio is restored, the copter will operate according to the GPS Rescue mode from the remote control and will automatically return to the start area and can be detected visually with subsequent control from the remote control.