Robotic Surveying of Apple Orchards

We present a novel system for surveying apple orchards by counting apples and estimating apple diameters. Existing surveying systems resort to active sensors, or high-resolution close-up images under controlled lighting conditions. The main novelty of our system is the use of a traditional low resolution stereo-system mounted on a small aerial vehicle. Vision processing in this set up is challenging because apples occupy a small number of pixels and are often occluded by either leaves or other apples. After presenting the system setup and our view-planning methodology, we present a novel method to match and combine multiple views of each apple and report successful results from field trials. We conclude the paper with an experimental analysis of the diameter estimation error.