Multifunctional Ground Control Points with a Wireless Network for Communication with a UAV.

Xiongzhe Han,William Rooney,Pappu Yadav,J Thomasson,Hussein Gharakhani,Yang Xiang

doi:10.3390/s19132852

Xiongzhe Han, William Rooney + Show 4 more

Open Access

https://doi.org/10.3390/s19132852

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Abstract

Ground control points (GCPs) are commonly used for georeferencing in remote sensing. Precise position measurement of the GCPs typically requires careful ground surveying, which is time-consuming and labor-intensive and thus excessively costly if it needs to be repeated multiple times in a season. A system of multifunctional GCPs and a wireless network for communication with an unmanned aerial vehicle (UAV) was developed to improve the speed of GCP setup and provide GCP data collection in real-time during the flight. While testing the system, a single-board computer on a fixed-wing UAV used in the study successfully recorded position data from all the GCPs during the flight. The multifunctional GCPs were also tested for use as references for calibration of reflectance and height for field objects like crops. The test of radiometric calibration resulted in an average reflectance error of 2.0% and a strong relationship (R2 = 0.99) between UAV-based estimates and ground reflectance. Furthermore, the average height difference between UAV-based height estimates and ground measurements was within 10 cm.

Highlights

Unmanned aerial vehicles (UAVs) are being used in agricultural research to collect images for various tasks including biomass monitoring, crop yield estimation, disease detection, and water status estimation [1,2,3]
The entire Ground control points (GCPs) system (Figure 1) includes a global positioning system (GPS) base-station with a main control terminal serving as a central coordinator, a laptop running a custom user interface to serve as a monitoring terminal for the experiment, several GCPs carrying subordinate GPS receivers, a fixed-wing UAV, and a wireless network with multiple hardware and software components
Differential-correction signals collected by the base station were transmitted through a universal asynchronous receiver/transmitter (UART) serial communication interface to the STM32 microcontroller, which broadcasted them to the GCPs through the XBee radio transceiver

Summary

Introduction

Unmanned aerial vehicles (UAVs) are being used in agricultural research to collect images for various tasks including biomass monitoring, crop yield estimation, disease detection, and water status estimation [1,2,3]. In transitioning, for these type of data to on-farm use, high accuracy is critical to reliable decision-making. Unless a direct georeferencing technique is used [9] Such GCPs are commonly used for georeferencing and are designed to be clearly visible and large enough in images so that a center point can be accurately and precisely marked from the flight altitude. GCPs should be spread across the ground area of the flight zone and should cover both high and low elevations [10]

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