Title
UAV Photogrammetry of Forests as a Vulnerable Process. A Sensitivity Analysis for a Structure from Motion RGB-Image Pipeline.
Abstract
Structural analysis of forests by UAV is currently growing in popularity. Given the reduction in platform costs, and the number of algorithms available to analyze data output, the number of applications has grown rapidly. Forest structures are not only linked to economic value in forestry, but also to biodiversity and vulnerability issues. LiDAR remains the most promising technique for forest structural assessment, but small LiDAR sensors suitable for UAV applications are expensive and are limited to a few manufactures. The estimation of 3D-structures from two-dimensional image sequences called Structure from motion' (SfM) overcomes this limitation by photogrammetrically reconstructing point clouds similar to those rendered from LiDAR sensors. The result of these techniques in highly structured terrain strongly depends on the methods employed during image acquisition, therefore structural indices might be vulnerable to misspecifications in flight campaigns. In this paper, we outline how image overlap and ground sampling distances affect image reconstruction completeness in 2D and 3D. Higher image overlaps and coarser GSDs have a clearly positive influence on reconstruction quality. Therefore, higher accuracy requirements in the GSD must be compensated by a higher image overlap. The best results are achieved with an image overlap of > 95% and a resolution of > 5 cm. The most important environmental factors have been found to be wind and terrain elevation, which could be an indicator of vegetation density.
Year
DOI
Venue
2018
10.3390/rs10060912
REMOTE SENSING
Keywords
Field
DocType
UAV,photogrammetry,SfM,image aggregation,forest,sensitivity analyses,reconstruction quality
Iterative reconstruction,Structure from motion,Photogrammetry,Computer vision,Remote sensing,Terrain,Lidar,Sampling (statistics),Artificial intelligence,Elevation,Geology,Point cloud
Journal
Volume
Issue
Citations 
10
6
1
PageRank 
References 
Authors
0.36
4
4
Name
Order
Citations
PageRank
Julian Frey110.70
Kyle Kovach210.36
Simon Stemmler310.36
Barbara Koch4878.38