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@ARTICLE{Pinto:829744,
      author       = {Pinto, Francisco and Müller-Linow, Mark and Schickling,
                      Anke and Cendrero, Pilar and Ballvora, Agim and Rascher,
                      Uwe},
      title        = {{M}ultiangular {O}bservation of {C}anopy {S}un-{I}nduced
                      {C}hlorophyll {F}luorescence by {C}ombining {I}maging
                      {S}pectroscopy and {S}tereoscopy},
      journal      = {Remote sensing},
      volume       = {9},
      number       = {5},
      issn         = {2072-4292},
      address      = {Basel},
      publisher    = {MDPI},
      reportid     = {FZJ-2017-03382},
      pages        = {415},
      year         = {2017},
      abstract     = {The effect that the canopy structure and the viewing
                      geometry have on the intensity and the spatial distribution
                      of passively measured sun-induced chlorophyll fluorescence
                      at canopy scale is still not well understood. These
                      uncertainties constrain the potential use of fluorescence to
                      quantify photosynthesis at this level. Using a novel
                      technique, we evaluated the diurnal changes in the spatial
                      distribution of sun-induced fluorescence at 760 nm (F760)
                      within the canopy as a consequence of the spatial
                      disposition of the leaves and the viewing angle of the
                      sensor. High resolution spectral and stereo images of a full
                      sugar beet canopy were recorded simultaneously in the field
                      to estimate maps of F760 and the surface angle distribution,
                      respectively. A dedicated algorithm was used to align both
                      maps in the post-processing and its accuracy was evaluated
                      using a sensitivity test. The relative angle between sun and
                      the leaf surfaces primarily determined the amount of
                      incident Photosynthetic Active Radiation (PAR), which in
                      turn was reflected in different values of F760, with the
                      highest values occurring in leaf surfaces that are
                      perpendicularly oriented to the sun. The viewing angle of
                      the sensor also had an impact in the intensity of the
                      recorded F760. Higher viewing angles generally resulted in
                      higher values of F760. We attribute these changes to a
                      direct effect of the vegetation directional reflectance
                      response on fluorescence retrieval. Consequently, at leaf
                      surface level, the spatio-temporal variations of F760 were
                      mainly explained by the sun–leaf–sensor geometry rather
                      than directionality of the fluorescence emission. At canopy
                      scale, the diurnal patterns of F760 observed on the
                      top-of-canopy were attributed to the complex interplay
                      between the light penetration into the canopy as a function
                      of the display of the various leaves and the fluorescence
                      emission of each leaf which is modulated by the exposure of
                      the individual leaf patch to the incoming light and the
                      functional status of photosynthesis. We expect that forward
                      modeling can help derive analytical simplified skeleton
                      assumptions to scale canopy measurements to the leaf
                      functional properties.},
      cin          = {IBG-2},
      ddc          = {620},
      cid          = {I:(DE-Juel1)IBG-2-20101118},
      pnm          = {582 - Plant Science (POF3-582) / DPPN - Deutsches Pflanzen
                      Phänotypisierungsnetzwerk (BMBF-031A053A) / BMBF-0315532A -
                      CROP.SENSe.net (BMBF-0315532A)},
      pid          = {G:(DE-HGF)POF3-582 / G:(DE-Juel1)BMBF-031A053A /
                      G:(DE-Juel1)BMBF-0315532A},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000402573700018},
      doi          = {10.3390/rs9050415},
      url          = {https://juser.fz-juelich.de/record/829744},
}