Current issue: 54(1)

Under compilation: 54(2)

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Silva Fennica 1926-1997
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Acta Forestalia Fennica
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Articles by Matti Mõttus

Category: Research article

article id 10270, category Research article
Aarne Hovi, Matti Mõttus, Jussi Juola, Farshid Manoocheri, Erkki Ikonen, Miina Rautiainen. (2020). Evaluating the performance of a double integrating sphere in measurement of reflectance, transmittance, and albedo of coniferous needles. Silva Fennica vol. 54 no. 2 article id 10270. https://doi.org/10.14214/sf.10270
Highlights: Adaptation of a compact double integrating sphere for spectral measurements of coniferous needles; Double integrating sphere is fast to operate and suitable for monitoring purposes and collection of large spectral databases; Measured spectra showed negative bias, which could potentially be reduced by building an optimized measurement setup.

Leaf reflectance and transmittance spectra are essential information in many applications such as developing remote sensing methods, computing shortwave energy balance (albedo) of forest canopies, and monitoring health or stress of trees. Measurement of coniferous needle spectra has usually been carried out with single integrating spheres, which has involved a lot of tedious manual work. A small double integrating sphere would make the measurements considerably faster, because of its ease of operation and small sample sizes required. Here we applied a compact double integrating sphere setup, used previously for measurement of broad leaves, for measurement of coniferous needles. Test measurements with the double integrating sphere showed relative underestimation of needle albedo by 5–39% compared to a well-established single integrating sphere setup. A small part of the bias can be explained by the bias of the single sphere. Yet the observed bias is quite significant if absolute accuracy of measurements is required. For relative measurements, e.g. for monitoring development of needle spectra over time, the double sphere system provides notable improvement. Furthermore, it might be possible to reduce the bias by building an optimized measurement setup that minimizes absorption losses in the sample port. Our study indicates that double spheres, after some technical improvement, may provide a new and fast way to collect extensive spectral libraries of tree species.

  • Hovi, Aalto University, School of Engineering, Department of Built Environment, P.O.Box 14100, FI-00760 Aalto, Finland ORCID ID: https://orcid.org/0000-0002-4384-5279 E-mail: aarne.hovi@aalto.fi (email)
  • Mõttus, VTT Technical Research Centre Finland, P.O. Box 1000, FI-02044 VTT, Finland ORCID ID: https://orcid.org/0000-0002-2745-1966 E-mail: matti.mottus@gmail.com
  • Juola, Aalto University, School of Engineering, Department of Built Environment, P.O.Box 14100, FI-00760 Aalto, Finland ORCID ID:E-mail: jussi.juola@aalto.fi
  • Manoocheri, Aalto University, School of Electrical Engineering, Metrology Research Institute, Maarintie 8, FI-02150 Espoo, Finland ORCID ID: https://orcid.org/0000-0003-3935-3930 E-mail: farshid.manoocheri@aalto.fi
  • Ikonen, VTT Technical Research Centre Finland, P.O. Box 1000, FI-02044 VTT, Finland; Aalto University, School of Electrical Engineering, Metrology Research Institute, Maarintie 8, FI-02150 Espoo, Finland ORCID ID: https://orcid.org/0000-0001-6444-5330 E-mail: erkki.ikonen@aalto.fi
  • Rautiainen, Aalto University, School of Engineering, Department of Built Environment, P.O.Box 14100, FI-00760 Aalto, Finland; Aalto University, School of Electrical Engineering, Department of Electronics and Nanoengineering, P.O. Box 15500, FI-00760 Aalto, Finland ORCID ID: https://orcid.org/0000-0002-6568-3258 E-mail: miina.a.rautiainen@aalto.fi
article id 261, category Research article
Miina Rautiainen, Matti Mõttus, Pauline Stenberg, Sanna Ervasti. (2008). Crown envelope shape measurements and models. Silva Fennica vol. 42 no. 1 article id 261. https://doi.org/10.14214/sf.261
This paper addresses tree crown envelope shape modeling from the perspective of optical passive remote sensing. The aims are 1) to review the specific requirements of crown shape models and ground measurement techniques in optical remote sensing, and 2) to present preliminary results from empirical, parametric crown shape and volume modeling of Scots pine and Norway spruce applicable in Finland. Results indicated that the basic dimensions (maximum radius, its height and crown length) of tree crowns were better predicted for pines, but the profile shape of the upper part of the crowns varied more than in spruce. Pine crowns were also slightly less concave than spruce crowns. No regularities were observed concerning the lower part of the crowns. The asymmetry of crowns increased as a function of tree age for both species, spruce crowns being more asymmetric than pine crowns. A comparison of measured crown volume with several simple geometrical crown shape envelopes showed that using a cone as a crown shape model for Scots pine and Norway spruce underestimates crown volume most severely. Other crown envelope shape models (e.g. ellipsoids) rendered crown volumes closer to the measured volume and did not differ considerably from each other.
  • Rautiainen, Tartu Observatory, 61602 Tõravere, Estonia, and Department of Forest Resource Management, P.O. Box 27, FI-00014 University of Helsinki, Finland ORCID ID:E-mail: miina.rautiainen@helsinki.fi (email)
  • Mõttus, Tartu Observatory, 61602 Tõravere, Estonia ORCID ID:E-mail:
  • Stenberg, Department of Forest Resource Management, P.O. Box 27, FI-00014 University of Helsinki, Finland ORCID ID:E-mail:
  • Ervasti, City of Vantaa, Land Use and Environment / Green Area Unit, Kielotie 13, FI-01300 Vantaa, Finland ORCID ID:E-mail:

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