Projekteja vuodessa
Abstrakti
Physically-based methods in remote sensing provide benefits over statistical approaches in monitoring biophysical characteristics of vegetation. However, physically-based models still demand large computational resources and often require rather detailed informative priors on various aspects of vegetation and atmospheric status. Spectral invariants and photon recollision probability theories provide a solid theoretical framework for developing relatively simple models of forest canopy reflectance. Empirical validation of these theories is, however, scarce. Here we present results of a first empirical validation of a model based on photon recollision probability at the level of individual trees. Multiangular spectra of pine, spruce, and oak tree seedlings (height = 0.38–0.7 m) were measured using a goniometer, and tree hemispherical reflectance was derived from those measurements. We evaluated the agreement between modeled and measured tree reflectance. The model predicted the spectral signatures of the tree seedlings in the wavelength range between 400 and 2300 nm well, with wavelength-specific bias between −0.048 and 0.034 in reflectance units. In relative terms, the model errors were the smallest in the near-infrared (relative RMSE up to 4%, 7%, and 4% for pine, spruce, and oak seedlings, respectively) and the largest in the visible wavelength region (relative RMSE up to 34%, 20%, and 60%). The errors in the visible region could be partly attributed to wavelength-dependent directional scattering properties of the leaves. Including woody parts of tree seedlings in the model improved the results by reducing the relative RMSE by up to 10% depending on species and wavelength. Spectrally invariant model parameters, i.e. total and directional escape probabilities, depended on spherically averaged silhouette to total area ratio (STAR) of the tree seedlings. Overall, the modeled and measured tree reflectance mainly agreed within measurement uncertainties, but the results indicate that the assumption of isotropic scattering by the leaves can result in large errors in the visible wavelength region for some tree species. Our results help increasing the confidence when using photon recollision probability and spectral invariants -based models to interpret satellite images, but they also lead to an improved understanding of the assumptions and limitations of these theories.
Alkuperäiskieli | Englanti |
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Sivut | 57-72 |
Sivumäärä | 16 |
Julkaisu | ISPRS Journal of Photogrammetry and Remote Sensing |
Vuosikerta | 169 |
DOI - pysyväislinkit | |
Tila | Julkaistu - marrask. 2020 |
OKM-julkaisutyyppi | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä |
Sormenjälki
Sukella tutkimusaiheisiin 'Empirical validation of photon recollision probability in single crowns of tree seedlings'. Ne muodostavat yhdessä ainutlaatuisen sormenjäljen.Projektit
- 2 Päättynyt
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FREEDLES: From needles to landscapes: a novel approach to scaling forest spectra
Rautiainen, M. (Vastuullinen tutkija), Hovi, A. (Projektin jäsen), Juola, J. (Projektin jäsen), Mercier, A. (Projektin jäsen), Salko, S.-S. (Projektin jäsen), Rönkkö, J. (Projektin jäsen), Karlqvist, S. (Projektin jäsen) & Schraik, D. (Projektin jäsen)
01/05/2018 → 30/04/2024
Projekti: EU: ERC grants
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BOREALITY: Boreaalisen metsän vuodenaikaisvaihteluiden mittaaminen avaruudesta: mikä on metsän albedon, tuotoksen ja fenologian yhteys?
Hovi, A. (Projektin jäsen), Rautiainen, M. (Vastuullinen tutkija), Majasalmi, T. (Projektin jäsen), Juola, J. (Projektin jäsen) & Palviainen, P. (Projektin jäsen)
01/09/2015 → 31/12/2019
Projekti: Academy of Finland: Other research funding
Laitteet
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i3 – Industry Innovation Infrastructure
Sainio, P. (Manager)
Insinööritieteiden korkeakouluLaitteistot/tilat: Facility
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Tutkimustuotos
- 9 Viittaukset
- 1 Comment/debate
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Corrigendum to “Empirical validation of photon recollision probability in single crowns of tree seedlings” [ISPRS J. Photogramm. Remote Sens. 169 (2020) 57–72] (ISPRS Journal of Photogrammetry and Remote Sensing (2020) 169 (57–72), (S0924271620302380), (10.1016/j.isprsjprs.2020.08.027))
Hovi, A., Forsström, P., Ghielmetti, G., Schaepman, M. E. & Rautiainen, M., elok. 2021, julkaisussa: ISPRS Journal of Photogrammetry and Remote Sensing. 178, s. 135 1 SivumääräTutkimustuotos: Lehtiartikkeli › Comment/debate › Scientific › vertaisarvioitu