Estimation of number and diameter of apple fruits in an orchard during the growing season by thermal imaging
A new method for estimating the number of apple fruits and measuring their diameter in the orchard was developed and tested. A thermal camera captured images of apple trees five times during the vegetation period JuneSeptember 2001. Each time 120 images of twenty apple trees were recorded late in the afternoon to achieve a temperature gradient between fruits and their background. Recorded images were processed using several image processing algorithms. Correlation coefficients R2 from 0.83 to 0.88 were established between the manually measured fruit number and the estimated number based on a fruit detection algorithm. According to fruit development and the established growing curve, the value of the correlation coefficient, R2, increased during the ripening period. For measuring the fruit's diameter values of R2 between 0.68 and 0.70 were established. These slightly increased according to the fruit's colour and size development during the ripening period.
diameters apples thermography image analysis yields