@article{fdi:010086810,
  title = {{P}eering through the thicket : effects of {UAV} {L}i{DAR} scanner settings and flight planning on canopy volume discovery},
  author = {{B}rede, {B}. and {B}artholomeus, {H}. {M}. and {B}arbier, {N}icolas and {P}imont, {F}. and {V}incent, {G}r{\'e}goire and {H}erold, {M}.},
  editor = {},
  language = {{ENG}},
  abstract = {{U}noccupied aerial vehicle laser scanning ({UAV}-{LS}) has been increasingly used for forest structure assessment in recent years due to the potential to directly estimate individual tree attributes and availability of commercial solutions. {H}owever, standardised procedures for campaign planning are still largely missing. {T}his study investigated scanner properties and flight planning to provide recommendations on minimising forest canopy occlusion and thereby maximise exploration of canopy volume. {A} flight campaign involving two {UAV}-{LS} systems was conducted over a dense, wet tropical forest at the {P}aracou research station ({F}rench {G}uiana). {F}our experiments on scanner properties and flight planning were conducted, analysed and recommendations derived. {F}irst, the scanner pulse repetition rate ({PRR}) should be at least 100 k{H}z per 1 m s-1flight speed based on 360 degrees {FOV} for exploration of middle canopy strata (5 m to 20 m). {H}igher {PRR} are beneficial for exploration of lower canopy (<5 m) but would need to be increased exponentially to achieve linear improvement. {A}lternatively, flight speed could be reduced within the constraints given by the inertial measurement unit ({IMU}), but would increase flight time. {S}econd, the scanner maximum range was identified as a proxy for the laser pulse power, which positively impacts canopy exploration. {T}his was particularly the case when using multi-return capabilities. {N}o saturation could be observed when increasing the laser power, suggesting that this is currently a limiting factor. {A}dditionally, a smaller laser beam divergence and pulse width were plausible reasons for better exploration of the upper canopy just below the top of canopy. {T}hird, off-nadir scanning angles up to 20 degrees were found to result in similar occlusions, suggesting a practical {FOV} of 40 degrees in the investigated dense forest. {T}his number might be larger for open canopies. {UAV}-{LS} systems with viewing geometries that focus laser pulses downwards and within optimal ranges should be preferred. {F}ourth, using different horizontal flight directions in the mission planning favours minimisation of occlusion. {A} minimum of two different flight directions is suggested. {H}owever, specific optimal yaw angles were not possible to predict before flight. {T}herefore, including multiple directions ensures coverage of all possible configurations. {M}any of these investigated features can be optimised independently from each other, and should be considered before acquisition of new {UAV}-{LS} systems and flight mission planning. {T}hese results support the establishment of general guidelines for the investment in {UAV}-{LS} systems and optimal mission planning for forest structure assessment.},
  keywords = {{U}noccupied aerial vehicle laser scanning ({UAV}-{LS}) ; {O}cclusion ; {F}orest structure},
  booktitle = {},
  journal = {{I}nternational {J}ournal of {A}pplied {E}arth {O}bservation and {G}eoinformation},
  volume = {114},
  numero = {},
  pages = {103056 [14 p.]},
  ISSN = {1569-8432},
  year = {2022},
  DOI = {10.1016/j.jag.2022.103056},
  URL = {https://www.documentation.ird.fr/hor/fdi:010086810},
}