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@ARTICLE{Burkart:276577,
      author       = {Burkart, Andreas and Aasen, Helge and Alonso, Luis and
                      Menz, Gunter and Bareth, Georg and Rascher, Uwe},
      title        = {{A}ngular {D}ependency of {H}yperspectral {M}easurements
                      over {W}heat {C}haracterized by a {N}ovel {UAV} {B}ased
                      {G}oniometer},
      journal      = {Remote sensing},
      volume       = {7},
      number       = {1},
      issn         = {2072-4292},
      address      = {Basel},
      publisher    = {MDPI},
      reportid     = {FZJ-2015-06942},
      pages        = {725 - 746},
      year         = {2015},
      abstract     = {In this study we present a hyperspectral flying goniometer
                      system, based on a rotary-wing unmanned aerial vehicle (UAV)
                      equipped with a spectrometer mounted on an active gimbal. We
                      show that this approach may be used to collect multiangular
                      hyperspectral data over vegetated environments. The pointing
                      and positioning accuracy are assessed using structure from
                      motion and vary from σ = 1° to 8° in pointing and σ =
                      0.7 to 0.8 m in positioning. We use a wheat dataset to
                      investigate the influence of angular effects on the NDVI,
                      TCARI and REIP vegetation indices. Angular effects caused
                      significant variations on the indices: NDVI = 0.83–0.95;
                      TCARI = 0.04–0.116; REIP = 729–735 nm. Our analysis
                      highlights the necessity to consider angular effects in
                      optical sensors when observing vegetation. We compare the
                      measurements of the UAV goniometer to the angular modules of
                      the SCOPE radiative transfer model. Model and measurements
                      are in high accordance (r2 = 0.88) in the infrared region at
                      angles close to nadir; in contrast the comparison show
                      discrepancies at low tilt angles (r2 = 0.25). This study
                      demonstrates that the UAV goniometer is a promising approach
                      for the fast and flexible assessment of angular effects.},
      cin          = {IBG-2},
      ddc          = {620},
      cid          = {I:(DE-Juel1)IBG-2-20101118},
      pnm          = {582 - Plant Science (POF3-582)},
      pid          = {G:(DE-HGF)POF3-582},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000348401900036},
      doi          = {10.3390/rs70100725},
      url          = {https://juser.fz-juelich.de/record/276577},
}