Consecutive monitoring method for pecan orchards with UAV

H. Yamagata, K. Noda, J. Randall, K. Oki
The use of remote sensing is useful to manage large scale croplands. However, there are limitations such as lack of the spatial resolution or high operative cost in remote sensing technologies using satellite sensors and manned airborne platforms. By using UAVs (unmanned aerial vehicles), we can solve those limitations and anyone can perform low cost and detailed cropland management. In this study, we established consecutive monitoring methods using UAV in pecan orchards of 64 ha each, in Arizona, USA. The UAV had two cameras of near infrared (0.7-1.0 μm, 4 cm resolution) and thermal infrared (8-13 μm, 40 cm resolution) and observations were performed once every two weeks. We made whole maps of each orchard by creating a mosaic of the images of both cameras. Furthermore, we can monitor changes at a spot in the orchard by maintaining positional information to a map. We monitored the activity of pecan trees by NDVI and thermal images, and tree height by DSM (digital surface model) which was made from a 3D model. Differences in growth of different cultivars of pecan trees was observed by monitoring the activity of the trees by NDVI. In addition, trees that had growth inhibition were detected from among the orchard. In the map made by thermal images, temperature was found to be higher in the areas that had originally cultivated alfalfa in center pivot irrigation, and lower in areas that there were not used for alfalfa cultivation. In the derived tree height map, tree height was estimated individually. By comparing tree height maps of different days, it is possible to estimate the amount of tree height growth during that period. By doing so, we can detect trees which grow remarkably or unsatisfactory in a vast orchard.
Yamagata, H., Noda, K., Randall, J. and Oki, K. (2021). Consecutive monitoring method for pecan orchards with UAV. Acta Hortic. 1318, 201-208
DOI: 10.17660/ActaHortic.2021.1318.29
remote sensing, unmanned aerial vehicles (UAVs), thermal, NDVI, pecan, 3D modeling

Acta Horticulturae