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Polarised multiangular reflectance measurements using the finnish geodetic institute field goniospectrometer.

Suomalainen J, Hakala T, Peltoniemi J, Puttonen E - Sensors (Basel) (2009)

Bottom Line: The angles are registered at accuracies better than 2°.During 2004 - 2008, FIGIFIGO has been used in the measurement of over 150 samples, all around northern Europe.The samples concentrate mostly on boreal forest understorey, snow, urban surfaces, and reflectance calibration surfaces.

View Article: PubMed Central - PubMed

Affiliation: Finnish Geodetic Institute, Box 15, 02431 Masala, Finland; E-Mails: teemu.hakala@fgi.fi (T.H.); jouni.peltoniemi@fgi.fi (J.P.); eetu.puttonen@fgi.fi (E.P.).

ABSTRACT
The design, operation, and properties of the Finnish Geodetic Institute Field Goniospectrometer (FIGIFIGO) are presented. FIGIFIGO is a portable instrument for the measurement of surface Bidirectional Reflectance Factor (BRF) for samples with diameters of 10 - 50 cm. A set of polarising optics enable the measurement of linearly polarised BRF over the full solar spectrum (350 - 2,500 nm). FIGIFIGO is designed mainly for field operation using sunlight, but operation in a laboratory environment is also possible. The acquired BRF have an accuracy of 1 - 5% depending on wavelength, sample properties, and measurement conditions. The angles are registered at accuracies better than 2°. During 2004 - 2008, FIGIFIGO has been used in the measurement of over 150 samples, all around northern Europe. The samples concentrate mostly on boreal forest understorey, snow, urban surfaces, and reflectance calibration surfaces.

No MeSH data available.


Typical noise levels in FIGIFIGO measurement of a white Spectralon panel. With darker samples, the noise levels are respectively higher. Sunlight measurement was made on an August afternoon in southern Finland (Sun zenith 54°). In the laboratory, the illumination zenith angle was approximately 45°. The sunlight spectrum shows increased noise at the atmospheric absorption bands around 1,200 nm, 1,400 nm, and 1,900. In the laboratory, the lower light levels enhance the noise at the spectrometer VNIR, SWIR1, and SWIR2 sensor borders (986 nm and 1,760 nm) as the sensitivities drops.
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f6-sensors-09-03891: Typical noise levels in FIGIFIGO measurement of a white Spectralon panel. With darker samples, the noise levels are respectively higher. Sunlight measurement was made on an August afternoon in southern Finland (Sun zenith 54°). In the laboratory, the illumination zenith angle was approximately 45°. The sunlight spectrum shows increased noise at the atmospheric absorption bands around 1,200 nm, 1,400 nm, and 1,900. In the laboratory, the lower light levels enhance the noise at the spectrometer VNIR, SWIR1, and SWIR2 sensor borders (986 nm and 1,760 nm) as the sensitivities drops.

Mentions: The error sources in FIGIFIGO radiometry follow generally the same principles as any spectrometer measurements. Noise in reflectance spectrum varies over wavelengths depending on sensor sensitivity and intensity of light. (Figure 6) In sunlight measurements, the noise is increased at the atmospheric absorption bands; around 1,200 nm, 1,400 nm, and 1,900 nm. In laboratory measurements, these absorption bands produce a decent signal, but otherwise the noise levels are the same or higher than in sunlight. Due to low irradiance of laboratory illumination, the spectrometer needs to use high gain at the SWIR sensors. Thus, also, noise at the borders of the SWIR sensor (986 nm and 1,760 nm) is amplified.


Polarised multiangular reflectance measurements using the finnish geodetic institute field goniospectrometer.

Suomalainen J, Hakala T, Peltoniemi J, Puttonen E - Sensors (Basel) (2009)

Typical noise levels in FIGIFIGO measurement of a white Spectralon panel. With darker samples, the noise levels are respectively higher. Sunlight measurement was made on an August afternoon in southern Finland (Sun zenith 54°). In the laboratory, the illumination zenith angle was approximately 45°. The sunlight spectrum shows increased noise at the atmospheric absorption bands around 1,200 nm, 1,400 nm, and 1,900. In the laboratory, the lower light levels enhance the noise at the spectrometer VNIR, SWIR1, and SWIR2 sensor borders (986 nm and 1,760 nm) as the sensitivities drops.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3297140&req=5

f6-sensors-09-03891: Typical noise levels in FIGIFIGO measurement of a white Spectralon panel. With darker samples, the noise levels are respectively higher. Sunlight measurement was made on an August afternoon in southern Finland (Sun zenith 54°). In the laboratory, the illumination zenith angle was approximately 45°. The sunlight spectrum shows increased noise at the atmospheric absorption bands around 1,200 nm, 1,400 nm, and 1,900. In the laboratory, the lower light levels enhance the noise at the spectrometer VNIR, SWIR1, and SWIR2 sensor borders (986 nm and 1,760 nm) as the sensitivities drops.
Mentions: The error sources in FIGIFIGO radiometry follow generally the same principles as any spectrometer measurements. Noise in reflectance spectrum varies over wavelengths depending on sensor sensitivity and intensity of light. (Figure 6) In sunlight measurements, the noise is increased at the atmospheric absorption bands; around 1,200 nm, 1,400 nm, and 1,900 nm. In laboratory measurements, these absorption bands produce a decent signal, but otherwise the noise levels are the same or higher than in sunlight. Due to low irradiance of laboratory illumination, the spectrometer needs to use high gain at the SWIR sensors. Thus, also, noise at the borders of the SWIR sensor (986 nm and 1,760 nm) is amplified.

Bottom Line: The angles are registered at accuracies better than 2°.During 2004 - 2008, FIGIFIGO has been used in the measurement of over 150 samples, all around northern Europe.The samples concentrate mostly on boreal forest understorey, snow, urban surfaces, and reflectance calibration surfaces.

View Article: PubMed Central - PubMed

Affiliation: Finnish Geodetic Institute, Box 15, 02431 Masala, Finland; E-Mails: teemu.hakala@fgi.fi (T.H.); jouni.peltoniemi@fgi.fi (J.P.); eetu.puttonen@fgi.fi (E.P.).

ABSTRACT
The design, operation, and properties of the Finnish Geodetic Institute Field Goniospectrometer (FIGIFIGO) are presented. FIGIFIGO is a portable instrument for the measurement of surface Bidirectional Reflectance Factor (BRF) for samples with diameters of 10 - 50 cm. A set of polarising optics enable the measurement of linearly polarised BRF over the full solar spectrum (350 - 2,500 nm). FIGIFIGO is designed mainly for field operation using sunlight, but operation in a laboratory environment is also possible. The acquired BRF have an accuracy of 1 - 5% depending on wavelength, sample properties, and measurement conditions. The angles are registered at accuracies better than 2°. During 2004 - 2008, FIGIFIGO has been used in the measurement of over 150 samples, all around northern Europe. The samples concentrate mostly on boreal forest understorey, snow, urban surfaces, and reflectance calibration surfaces.

No MeSH data available.