# 3-dimensional surface geometry, optical properties dataset of Scots pine and Norway spruce shoots

## TL;DR

This paper introduces a detailed dataset of 3D geometry and optical properties of conifer shoots to improve understanding of light scattering in tree crowns.

## Contribution

The dataset provides high-resolution 3D and optical data for 27 conifer shoots, enabling more accurate radiative transfer modeling.

## Key findings

- High-resolution 3D point cloud representations of conifer shoots were created using blue light photogrammetry.
- Optical properties of needles and twigs were measured across a 400-2000 nm spectral range.
- The dataset supports improved modeling of light scattering in coniferous tree crowns.

## Abstract

Conifer shoots possess highly complex geometrical structures at a very fine spatial resolution. Accurately characterizing the full architecture of a conifer shoot, which influences how radiation is scattered, has proven challenging. Previous radiative transfer models for coniferous stands have represented these structures in a relatively simplified or coarse manner. This paper presents a dataset that can be used for up-scaling of needle to shoot optical properties and studying the influence of detailed three-dimensional (3D) structure of shoot to light scattering within tree crown. The dataset includes 3D structural information as well optical properties of needles and twigs for 27 shoots of two conifer species present in both locations (3 shoots per species and position in the crown) - Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies L. Karst.). The samples were collected on 22nd April 2024 in Rájec, the Czech Republic and 17th September 2024 in Järvselja, Estonia. Subsequently blue light 3D photogrammetry scanning technique was used to obtain their high-resolution 3D point cloud representations. Reflectance and transmittance measurements of needles were obtained using a spectroradiometer and an integrating sphere. For each of these samples, the dataset comprises a photo of the sampled shoot, obtained 3D surface reconstruction, and optical properties of conifer needles and twigs (hemispherical-conical reflectance and transmittance factors) in the spectral range of 400-2000 nm. A detailed 3D representation of needle shoots, when combined with radiative transfer modeling, may offer a means to study and compensate for inaccuracies in the measurement of needle optical properties and to enhance the assessment of shoot scattering characteristics.