High-precision GNSS for agricultural operations

Abstract Nowadays, a precise management of agricultural inputs based on spatial variability has become possible due to the availability of new technologies, including Global Navigation Satellite System (GNSS), unmanned aerial vehicles in agriculture (UAVs), high-resolution remote sensing, sensors to measure soil and plant characteristics, and controllers to guide agricultural machinery and apply precise amount of inputs. The benefits of precision agriculture are as follows: • The return on the investment from crop production may be increased by improvements in yield and/or a reduction in inputs; • The risk of environmental pollution from over application of agrochemicals that are associated with traditional agriculture can be reduced; • Greater product quality assurance achieved from precise targeting and recording of field applications that improve traceability. In the last decade, the number of fully operational and commercially available GNSS has increased. These systems provide accurate, continuous, geographic position and speed information in three dimensions and under all weather conditions to users 24 h a day. In the last two decades, the ability of Differential Global Positioning System to provide real-time, submeter- or even decimeter-level accuracy has revolutionized the agricultural industry. Applications of GNSS for agricultural purposes have thrived in recent years, and the literature is rich with numerous interesting examples. In this chapter, we limit our attention to five specific applications with which the authors are very closely involved: (1) GNSS in crop protection, (2) in variable rate application (VRA), (3) monitoring soil, plants, and production, (4) agricultural UAVs, and (5) ground platforms and autonomous tractors. Not all the operations in precision agriculture need the same level of accuracy. Most of them, such as yield monitoring or VRAs, can be accomplished satisfactorily with DGNSS that has submeter accuracy. Only some operations, however, demand high (~10 mm range) geopositioning accuracy and precision, such as a plant-specific operation, precision guidance, and controlled traffic farming. This level of accuracy could be achieved with the use of real-time kinematic Global Positioning System.