Short Communication. Using high resolution UAV imagery to estimate tree variables in Pinus pinea plantation in Portugal

Abstract

Aim of study: The study aims to analyse the potential use of lowcost unmanned aerial vehicle (UAV) imagery for the estimation of Pinus pinea L. variables at the individual tree level (position, tree height and crown diameter).Area of study: This study was conducted under the PINEA project focused on 16 ha of umbrella pine afforestation (Portugal) subjected to different treatments.Material and methods: The workflow involved: a) image acquisition with consumer-grade cameras on board an UAV; b) orthomosaic and digital surface model (DSM) generation using structure-from-motion (SfM) image reconstruction; and c) automatic individual tree segmentation by using a mixed pixel-and region-based algorithm.Main results: The results of individual tree segmentation (position, height and crown diameter) were validated using field measurements from 3 inventory plots in the study area. All the trees of the plots were correctly detected. The RMSE values for the predicted heights and crown widths were 0.45 m and 0.63 m, respectively.Research highlights: The results demonstrate that tree variables can be automatically extracted from high resolution imagery. We highlight the use of UAV as a fast, reliable and cost-effective technique for small scale applications.

Accuracy of Photogrammetric UAV-Based Point Clouds under Conditions of Partially-Open Forest Canopy

“…The RMSE xy differences between the GCP configurations are in the range of 4 mm for the "Kremnica Mountains" plot. For the "High Tatras" site, the RMSE xy is decreasing with an increasing number of GCPs (4,5,7,9), but the lowest RMSE xy was achieved using the four-GCP "cross" configuration. On the contrary, the RMSE xy of the "cross" configuration is the highest for the "Modrý Kameň" plot, while the difference between other configurations is within eight millimetres.…”

“…In forestry applications, researchers are focusing on the estimation of forest inventory and crown parameters [2][3][4][5][6][7][8][9][10][11], real-time and post-forest fire monitoring and detection [12][13][14], health status and disease monitoring [15][16][17], individual trees and species detection [18][19][20], or surveying the current state of soil displacement [21]. RGB or NIR (near infrared) cameras are used in the majority of these studies.…”

Evaluation of Close-Range Photogrammetry Image Collection Methods for Estimating Tree Diameters

“…The use of CRP for forestry is an emerging topic; the combination of CRP and unmanned aerial vehicles (UAV) can potentially revolutionize information collection methods for forests and individual trees [18][19][20][21][22][23]. The main advantage of terrestrial CRP is that it produces similar outputs with lower hardware costs when compared to TLS systems.…”

Investigation of the potential of drone observations for detection of forest disturbance caused by heavy snow damage in a Japanese cedar (<I>Cryptomeria japonica</I>) forest

“…Remote sensing using small drones equipped with GPS navigation and a digital camera might allow affordable and flexible detection of such narrow disturbance patches. In particular, structure from motion SfM photogrammetry using data obtained from drone observations would allow evaluation of the structural characteristics of the forest canopy from three-dimensional images such as tree height Guerra-Hernández et al, 2016;Wallace et al, 2016;Panagiotidis et al, 2017, crown diameter Guerra-Hernández et al, 2016Panagiotidis et al, 2017 , and individual trees Mohan et al, 2017 . The purpose of the present study was to clarify the possible usability of observations obtained from a small drone equipped with a GPS autopilot flight system and a digital camera to detect forest disturbance caused by heavy snow. To achieve this aim, we conducted drone observations in a long-term ecological research plot in a Japanese cedar forest in Japan, in which heavy forest disturbance was caused by snow damage in mid-December 2014.…”