On-the-Fly Tree Caliper Measurement
In fruit and shade tree nurseries, there is a need to count and measure caliper for trees frequently so as to have an accurate inventory sufficiently before harvest since disease, pests and climate can change the yield from year to year. In some tree nurseries it is common practice to count the entire stock three times a year and to caliper them once a year. Both tasks are very labor intensive, involving crews of workers counting trees by hand over several weeks. Experience indicates that calipering and counting millions of trees manually can be error prone. There is a strong need to automate these tasks in the tree nursery industry to decrease labor cost and to improve inventory management. We have developed a device to count trees and to measure caliper while the trees are in the field. The device is designed to be mounted on a carrier passing through rows of trees in a nursery. Tedious tasks are reduced to a simple drive through that could be done simultaneously with tasks such as spraying or mowing. Here we describe the device and results from tests conducted in nurseries in Pennsylvania in 2010. Our experiments show that it is reasonable to expect an accuracy of approximately ±1 mm indoors and ±2.5 mm outdoors.