As the involved rock volumes/masses increase, the complexity of conducting field-test experiments to build up rockfall databases increases to a point where such experiments become impracticable. Additionally, such rockfall data can serve as a base for assessing the model’s sensitivity to different parameters, evaluating their predictability and helping calibrate the model’s parameters from back calculation and analyses. As no model is perfect, their development is often accompanied and validated by the valuable collection of rockfall databases covering a range of site geometries, rock masses, velocities, and related energies that the models are designed for. Process-based rockfall simulation models attempt to better emulate rockfall dynamics to different degrees. Growth in knowledge about this most elementary yet often overlooked level of foliage clumping in canopies shall improve coniferous forest 3D radiative transfer modeling. The demonstrated effectiveness and performance of the blue light 3D photogrammetry scanning method shall lead to more frequent actual measurements of 3D shoot structures. The needle-to-shoot area ratio values were similar to those measured using the traditional combined photographic/volume displacement method. Karst.)-collected from trees in the Järvselja RAdiation transfer Model Intercomparison (RAMI) pine stand in Estonia. We used shoots of two species-Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies L. ![]() We validate the approach by comparing it to the combined photographic/volume displacement method-an established methodology for quantifying shoot-level clumping. We introduce blue light 3D photogrammetry scanning as a highly efficient technique for estimating shoot-level clumping, which significantly reduces the labor intensity aspect of the previous approaches. Previous methods for estimating the needle-to-shoot-area ratio have had in common destructive and/or highly labor-intensive aspects. Clumping of needles in shoots in conifer stands has posed a challenge because optical instruments have generally been incapable of measuring gaps between needles within a shoot. Clumping information is important for determining the radiation transfer through canopies, photosynthesis, and hydrological processes.
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