Research article - Peer-reviewed, 2017
Estimating vertical canopy cover using dense image-based point cloud data in four vegetation types in southern Sweden
Granholm, Ann-Helen; Lindgren, Nils; Olofsson, Kenneth; Nystrom, Mattias; Allard, Anna; Olsson, HakanAbstract
This study had the aim of investigating the utility of image-based point cloud data for estimation of vertical canopy cover (VCC). An accurate measure of VCC based on photogrammetric matching of aerial images would aid in vegetation mapping, especially in areas where aerial imagery is acquired regularly. The test area is located in southern Sweden and was divided into four vegetation types with sparse to dense tree cover: unmanaged coniferous forest; pasture areas with deciduous tree cover; wetland; and managed coniferous forest. Aerial imagery with a ground sample distance of 0.24 m was photogrammetrically matched to produce dense image-based point cloud data. Two different image matching software solutions were used and compared: MATCH-T DSM by Trimble and SURE by nFrames. The image-based point clouds were normalized using a digital terrain model derived from airborne laser scanner (ALS) data. The canopy cover metric vegetation ratio was derived from the image-based point clouds, as well as from raster-based canopy height models (CHMs) derived from the point clouds. Regression analysis was applied with vegetation ratio derived from near nadir ALS data as the dependent variable and metrics derived from image-based point cloud data as the independent variables. Among the different vegetation types, vegetation ratio derived from the image-based point cloud data generated by using MATCH-T resulted in relative root mean square errors (rRMSE) of VCC ranging from 6.1% to 29.3%. Vegetation ratio based on point clouds from SURE resulted in rRMSEs ranging from 7.3% to 37.9%. Use of the vegetation ratio based on CHMs generated from the image-based point clouds resulted in similar, yet slightly higher values of rRMSE.Published in
International Journal of Remote Sensing2017, volume: 38, number: 7, pages: 1820-1838
Authors' information
Swedish University of Agricultural Sciences, Department of Forest Resource Management
Lindgren, Nils
Swedish University of Agricultural Sciences, Department of Forest Resource Management
Swedish University of Agricultural Sciences, Department of Forest Resource Management
Swedish University of Agricultural Sciences, Department of Forest Resource Management
Swedish University of Agricultural Sciences, Department of Forest Resource Management
Swedish University of Agricultural Sciences, Department of Forest Resource Management
Associated SLU-program
Remningstorp
UKÄ Subject classification
Remote Sensing
Environmental Sciences related to Agriculture and Land-use
Forest Science
Publication Identifiers
DOI: https://doi.org/10.1080/01431161.2017.1283074
URI (permanent link to this page)
https://res.slu.se/id/publ/79930