Unmanned aerial systems for precision forest inventory purposes: A review and case study

Abstract

Unmanned Aerial Systems (UAS) are capable of improving the efficiency of acquisition and providing fine spatial scale data for sustainable resource management. In this paper we begin by describing differences between UAS airframes, their successes and limitations, and list contemporary research applications. UAS compatible sensor technologies are discussed, including passive and active sensors. Finally, we detail a case study where UAS updated an Enhanced Forest Inventory (EFI) for a study area in interior British Columbia. Airborne Laser Scanning (ALS) from 2013 and Digital Aerial Photogrammetric (DAP) point clouds acquired using a UAS from 2015 were used to estimate individual tree height and volume increments. A total of 246 trees were detected using Canopy Height Models (CHMs) with 70% of these trees being matched in the ALS and DAP data sets. Mean tree growth between 2013 and 2015 from the CHM and 95 th percentile of height (P95) was estimated at 0.68 ± 0.05 and 0.50 m ± 0.05 m, respectively. Similarly, mean gross tree volume increments (m 3 ) were computed as 0.05 m 3 ± 0.005 m 3 and 0.03 m 3 ± 0.005 m 3 for the CHM and P95, respectively. The results indicate that information from UAS-DAP point clouds can generate spatially and temporally accurate inventories and have potential to inform a number of sustainable forest management activities.

Estimating Tree Height and Diameter at Breast Height (DBH) from Digital Surface Models and Orthophotos Obtained with an Unmanned Aerial System for a Japanese Cypress (Chamaecyparis obtusa) Forest

“…Recent studies have reported the use of UAS in various analyses, including forestry applications [27,28]. Collecting aerial photos by UAS and processing them with the structure from motion (SfM) method is one of the major new approaches to analyzing forest structures [29,30].…”

Assessing Biodiversity in Boreal Forests with UAV-Based Photogrammetric Point Clouds and Hyperspectral Imaging

“…During recent years, the use of unmanned aerial vehicles (UAVs) in support of forest science has increased rapidly [37][38][39]. The use of UAVs has enabled the on-demand collection of high spatial resolution imagery, serving to improve the resolution of photogrammetric point clouds, and therefore offer improved characterization of forest structure [40,41].…”

“…In [37], it was suggested that UAVs could be used in identifying forest areas in need for management, such as thinning or fertilizer to concentrate activities for those and increase efficiency that way. Similarly in assessing biodiversity, UAVs can be seen as support tool when planning field campaigns.…”

“…For example, in multi-phase sampling where airborne or satellite data are usually used for stratifying the first phase of sampling for biodiversity mapping, UAVs could be used in second phase before determining the final field plots. In other words, data from a UAV would be complementary for part of the traditional field measurements that can be accurately derived from UAV data (e.g., vegetation height, canopy gaps) [37,43,51].…”

Uav-Based Photogrammetric Point Clouds and Hyperspectral Imaging for Mapping Biodiversity Indicators in Boreal Forests

“…Small unmanned aerial vehicles (UAVs) have been used increasingly as a data collection option to support forest sciences and applications (Goodbody et al 2017, Pajares 2015, Torresan et al, 2017. The use of UAVs has enabled the on-demand collection of high spatial resolution imagery, serving to improve the resolution of photogrammetric point clouds, and therefore offer improved characterization of forest structure.…”