CIOP   05384
CENTRO DE INVESTIGACIONES OPTICAS
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Crop field reflectance measurements
Autor/es:
WEBER, C.; SCHINCA, D.C., TOCHO, J.O.; VIDELA, F.A.
Lugar:
Campinas, Brasil
Reunión:
Congreso; Iberoamerican Conference on Optics (RIAO), Latinamerican meeting on Optics, Lasers and Applications (OPTILAS); 2007
Institución organizadora:
Sociedad Brasilera de Física
Resumen:
We present in this paper the results of re°ectance measurements performed with a three-band passive radiometer with independent channels for solar irradiance reference. The comparative operation of the traditional method that alternatively uses measurements of the field (downward-looking) and a white panel for reference (downard-looking) and the new approach that involves duplicated spectral channels, each one with its own diffuser that point upwards to the zenith direction upward-looking) is analyzed. The results indicated that the latter method is more suitable for use with passive sensors under rapid changing atmospheric conditions(such as clouds, dust, mist, smog and other scatterers), since a more reliable synchronic record of reference and incident light is achieved. Besides, having separate channels for the reference and the signal allow a betterbalancing of gains in the amplifiers for each spectral channel. We show the results obtained in the determination of the Normalized Difference Vegetation Index (NDVI) corresponding to 2006 and 2007 field experiments concerning weeds detection and fertilizer levels assessing in wheat, to refine sensor-based fertilizer nitrogen rate recommendations. It is also shown the variation of the radiometric normalization measurements taken at noon (nadir solar position) for the whole culture cycle corresponding to two seasons (winter and spring).