Returns the indices of the cylinders belonging to the crown of the treeQSM.
Arguments
- cylinder
Cylinder field of a TreeQSM that is returned by
read_tree_qsm.
Details
The crownset is determined based on four steps (that are designed to exclude dead branches at the bottom of the stem) according to Akerblom et al. (2017). STEP 1: Initialize the crown set as cylinders that have a branching order higher than three. If the initial set is empty, the minimum order is lowered until the set becomes non-empty. STEP 2: As long as the crown set extends, append the parent cylinders of the crown set that are not part of the stem. STEP 3: Append to the crown set cylinders that are not part of the stem but whose start point is higher than the lowest starting point of crown cylinders connected to the stem. STEP 4: As long as the crown set extends, append the child cylinders of the crown set.
References
Akerblom, M., Raumonen, P., Makipaa, R., & Kaasalainen, M. (2017). Automatic tree species recognition with quantitative structure models. Remote Sensing of Environment, 191, 1-12.
Examples
if (FALSE) {
# Read tree qsm and extract the crownset
qsm <- read_tree_qsm(QSM_path = "path/to/qsm.mat")
crown <- crownset_qsm(cylinder = qsm$cylinder)
}