Abstract
Abstract. Grassland ecology experiments in remote locations requiring quantitative analysis of the biomass in defined plots are becoming increasingly widespread, but are still limited by manual sampling methodologies. To provide a cost-effective automated solution for biomass determination, several photogrammetric techniques are examined to generate 3D point cloud representations of plots as a basis, to estimate aboveground biomass on grassland plots, which is a key ecosystem variable used in many experiments. Methods investigated include Structure from Motion (SfM) techniques for camera pose estimation with posterior dense matching as well as the usage of a Time of Flight (TOF) 3D camera, a laser light sheet triangulation system and a coded light projection system. In this context, plants of small scales (herbage) and medium scales are observed. In the first pilot study presented here, the best results are obtained by applying dense matching after SfM, ideal for integration into distributed experiment networks.
Highlights
Distributed experiment networks have recently emerged as a powerful tool for environmental research across spatial and temporal scales
One example is the Nutrient Network (NutNet). collaborative composed of over 40 replicated grassland plot experiment sites spread throughout six continents
Due to the filigree structure of grassland plot vegetation, 3D representations provided by any photogrammetric technique will never be perfectly complete, and the volume derived from a subsequent 3D surface model is not equal to biomass
Summary
Distributed experiment networks have recently emerged as a powerful tool for environmental research across spatial and temporal scales. The current standard for sampling aboveground biomass is by harvesting a portion of the plot, drying the harvest and weighing it - obviously a destructive method with potentially impacts on the plot. Photogrammetry promises efficient techniques to provide detailed 3D representations of grassland plot vegetation as a basis for biomass estimation, and complementary to the standard destructive methods. Due to the filigree structure of grassland plot vegetation, 3D representations provided by any photogrammetric technique will never be perfectly complete, and the volume derived from a subsequent 3D surface model is not equal to biomass. A quantitative relation between the ✝ Corresponding author volume derived from 3D representations of plot vegetation and the actual plot biomass has to be established by imaging and harvesting representative sample plots in different scales, which is not addressed in the paper
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