Remote sensing technologies for Precision Agricultural Aviation (PAA)

Recent increase in world’s population has necessitated the need for boosting production in agriculture to meet the ever increasing population. The continuous application of chemical pesticides to promote crop protection programs is paramount (Glass et al., 2010; Popp et al., 2013). Pesticide usage has become an integral component of modern agriculture and has contributed to improved productivity and crop quality (Oerke & Dehne, 2004; Hilz & Vermeer, 2013) and minimizing food loss up to about 45% globally (Oerke, 2006). The potential adverse effects of chemical pesticides use are enormous (Van der Werf, 1996; Wilson & Tisdell, 2001) and now there have been important policies and conventions put in place to strengthen the management of non-point source pollution from agriculture and the promotion of low-toxicity and low-residue pesticides.

Precision Agricultural Aviation (PAA) Technologies (PAAT) have rapidly developed in recent years attracting the attention by the government departments and farm users as a very effective means to reduce pesticide residues and adverse impacts on the environment while enhancing the pesticide effectiveness (Lan et al., 2017). Several technologies have been applied to aerial applicators including global positioning systems (GPS) and geographic information systems (GIS), soil mapping, yield monitoring, nutrient management field mapping, aerial photography and variable-rate (VR) controllers. In addition, developing of new nozzle types like pulse width modulation (PWM) and variable-rate nozzles can be integrated into these other systems to enhance application efficiency.

Further, ground verification technologies including prediction models of droplet deposition and droplet detection sensors, allow for quick confirmation and optimization of Precision agriculture aviation technologies. Since the design and development of the first variable rate controllers (VR) decades ago, aerial application systems have provided applicators the ability to precisely apply products such as cotton growth regulators, defoliants, and insecticides using prescription maps developed using remote sensing and GPS/GIS technologies.

Precision Agriculture technologies benefit the agricultural aviation sector through time and money savings. Airborne remote sensing allows for a new revenue source to agricultural aviators through remote sensing (RS) missions that would coincide with aerial spray applications (Lan et al., 2010). Remote sensing systems have provided precise images for spatial analyses of plant stress due to water or nutrient status in the field, disease, and pest infestations. However, due to differences in biological characteristics occurring naturally and incidences of diseases and insects, the interactions among these factors combine to influence crop quality and yield. Understanding of field and plant conditions can be increased

by spatial statistics.

Remote sensing data are converted into prescription maps for variable-rate aerial application through image processing (Lan et al., 2010, 2017). In order to modify and optimize the setup and operations of aerial spray systems, ground verification technologies (GVT) are very essential for characterizing spray droplet deposition data. Remote sensing, aerial spraying and ground verification technologies all combine to therefore develop Precision Agricultural Aviation Technology for use in agricultural protection and production practices (Lan et al., 2017).

In solving the bottleneck constraints in the development and application of precision agriculture, it is necessary to acquire and analyze crop information rapidly since it forms the basis for carrying out precision agricultural practices (Earl et al., 1996; Lan et al., 2017). With the rapid increase in population globally and the need to increase agricultural productivity, an urgent need to improve the management of agricultural resources. To assist farmers to improve the economic and environmental benefits of crop pest management through precision agriculture, remote sensing is being integrated with GPS, GIS, and VR technologies (Lan et al., 2009).

Remote sensing technologies have been developed rapidly and are recognized as one of the most important areas in the development of PAAT recently (Lan et al., 2010), making available imagery data for crop diseases and insect pests at different spatial, spectral and temporal resolutions, ultimately providing guidance in aerial application decisions (Lan et al., 2017). Satellite-based remote sensing platforms are macroscopic, fast, accurate, dynamic and are capable of providing abundant information, which are usually used to offer guidance in global agricultural production.

Satellite-based remote sensing has been characterized to; study crop diseases using multi-spectral remote sensing (Jonas & Gunter, 2007); produce risk maps for agricultural pests with a degree of spatial and temporal detail based on satellite remote sensing data and surface temperature data (Silva et al., 2015) and to establish of LST and modified normalized difference water index (MNDWI) of wheat, to discriminate the wheat aphid damage degrees over a large scale using only thermal infrared band and multispectral satellite imagery with an overall accuracy of 84% (Luo et al., 2012).

However, airborne remote sensing platforms offer a flexible and versatile operation allowing for images of fields to be taken at variable altitudes depending on the spatial resolution required. It also has the potential advantage of generating additional revenue source for aerial applicators since agricultural aircraft are easier to be scheduled for frequent remote sensing missions coinciding with aerial spray applications. In recent times, airborne remote sensing technologies have made incredible developments and are presently incorporated into precision agricultural applications (Lan et al., 2007; Huang et al., 2008, 2010).

Furthermore, UAV technologies have the advantages of simple construction, low operation and maintenance cost, compact and light weight footprint, simple operation and high flexibility as remote sensing platforms (Rango et al., 2006, 2009; Lan et al., 2017). The monitoring of crops on small and medium scales in agricultural remote sensing has greatly been expanded as a result of the development of UAV-based remote sensing technologies.

Researches have shown that the remote sensing images obtained by UAV-based LARS platform are easier and cheaper than other remote sensing methods (Chosa et al., 2010); can replace the satellite images to estimate the yield and biomass of crops (Sugiura et al., 2003, 2005; Swain et al., 2010); study crop response to irrigation and crop residue management (Sullivan et al., 2007) among others.