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Virtual Orchard: A Novel Approach to Generate 3D Point Cloud of Canopy Profile and Extract Tree Geometry
1A. Pourreza, 2G. Zuniga-Ramirez
1. University of California, Davis
2. University of California - Division of Agriculture and Natural Resources

Tree geometry such as volume, height, and width are important information that can help growers to conduct a precise orchard management. Conventionally, canopy profile is generated by using light detection and ranging (LIDAR) technology as a method for direct measurement of tree structure. While LIDAR is a precise method for generating 3D models of trees, it requires expertise, and expensive equipment that limits its application for creating 3D maps in large orchards. In this paper, an affordable and simple method for generating a 3D reconstruction of an orchard, called Virtual Orchard, was introduced and its capabilities were evaluated. Virtual Orchards for almond, citrus, pistachio, and vineyard were created by photogrammetry technique using a series of aerial images of orchard/vineyard acquired by an unmanned aerial system from various angles and heights. Orchard topography and digital surface model (DSM) were extracted from a point cloud dataset created by Virtual Orchard technology. An algorithm was developed to identify and locate individual trees in a virtual orchard and extract information such as canopy cover, maximum height, average height, area, width, and volume index. This information can be further analyzed and interpreted by prediction models to generate useful and timely prescription maps for precision agriculture practice. Virtual Orchards were also developed in non-visible bands such as near infrared (NIR, at about 800 nm) and red edge (680-740 nm). NIR imagery indicates plant vigor, in which a lower NIR value usually means that plant is under stress. Additionally, NIR could be used for normalizing chlorophyll-sensitive bands (e.g. Red band) and creating vegetation indices such as NDVI. Red-edge is another non-visible band that includes important information about plant stress, chlorophyll, and nitrogen content. Lower values in red-edge band usually indicate that plant is under nitrogen stress. Virtual Orchard in non-visible band could illustrate plant reflectance not only on tree crowns, but also on the sides of each tree. The virtual orchard technology demonstrated the potential to help growers conduct a precise management to improve yield, decrease waste, and maintain the quality of the environment.

Keyword: virtual orchard, point cloud, photogrammetry, unmanned aerial system, 3D map