Tree Crown Determination Using Terrestrial Imaging for Laser Scanned Individual Tree Recognition

A method to measure tree crown dimensions is introduced in this article. The method is based on terrestrial images, which are captured from two different directions. Image orientation is registered during the image acquisition and this geometrical information is utilized in image pre-processing. In pre-processing images are corrected from distortion errors and rectified to plane parallel to tree trunk. Parameters measured from the images are tree height, crown height and crown widths at several heights. Trunk tilting is calculated estimating trunk as three-dimensional vector and determining its parameters from trunk projections in image planes. Special attention is paid to orientation errors, which effects dimension measurement. Errors in ω, φ and κ and error in scale are analysed separately. Study aimed at developing method, which would not require special instruments, time consuming tacheometer measurement or positioning of image capture location. The method development initiated from the need to collect reference material for laser scanned tree crown study. Laser scanning data has been successfully used for single tree wise forest inventory. In forest area, first returns are typically reflections from the top of tree crowns. In addition to pulses reflected from tree crown top, several pulses also reflect from crown sides and inside crown. Utilising these echoes, information below the crown surface is attained. Reference data of captured trees has been previously obtained with tacheometer and hypsometer measurements. However, these measurements didn’t include information below crown top. With method suggested in this article that missing information is provided. It was expected that reference material provided with method would be accurate enough to be utilized as reference material for laser scanning tree crown study.