on 8 July 1997 over the Le Peyne test site in southern France. ... endmembers, the vegetation index values in the corresponding ROI is calculated ...... la Structure, de la Biomasse et de la Minйralomasse d'un Taillis Overt de Chкne Vert.
int. j. remote sensing, 2001, vol. 22, no. 17, 3381 –3396
Spatial scale variations in vegetation indices and above-ground biomass estimates: implications for MERIS
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F. VAN DER MEER*§, W. BAKKER*, K. SCHOLTE*¶, A. SKIDMORE*, S. DE JONG†, J. CLEVERS‡, E. ADDINK‡ and G. EPEMA‡ *International Institute for Aerospace Survey and Earth Sciences (ITC), Division of Geological Survey, P.O. Box 6, 7500 AA Enschede, the Netherlands †University of Utrecht, Department of Physical Geography, P.O.z Box 80115, 3508 TC Utrecht, the Netherlands ‡Wageningen University and Research Centre, Centre for Geoinformation, P.O. Box 339, 6700 AH Wageningen, the Netherlands § Delft University of Technology, Faculty of Civil Engineering and Geosciences, Department of Applied Earth Sciences, Mijnbouwstraat 120, P.O. Box 5028, 2600 GA Delft, the Netherlands (Received 6 December 1999; in nal form 5 June 2000) Abstract. The Medium Resolution Imaging Spectrometer (MERIS) is one of the sensors carried by Envisat. MERIS is a fully programmable imaging spectrometer, however a standard 15-channel band set will be transmitted for each 300 m pixel (over land while over the ocean the pixels will be aggregated to 1200 m spatial resolution) covering visible and near-infrared wavelengths. Since MERIS is a multidisciplinary sensor providing data that can be input into ecosystem models at various scales, we studied MERIS’s performance relative to the scale of observation using simulated datasets degraded to various spatial resolutions in the range of 6–300 m. Algorithms to simulate MERIS data using airborne imaging spectrometer datasets were presented, including a case study from DAIS (i.e. Digital Airborne Imaging Spectrometer) 79-channel imaging spectrometer data acquired on 8 July 1997 over the Le Peyne test site in southern France. For selected target endmembers garrigue, maquis, mixed oak forest, pine forest and bare agricultural eld, regions-of-interest (ROI) were dened in the DAIS scene. For each of the endmembers, the vegetation index values in the corresponding ROI is calculated for the MERIS data at the spatial resolutions ranging from 6 to 300 m. We applied the NDVI, PVI, WDVI, SAVI, MSAVI, MSAVI2 and GEMI vegetation indices. Above-ground biomass (AGB) was estimated in the eld and derived from the DAIS image and the MERIS datasets (6–300 m spatial resolution). The vegetation indices are shown to be constant with the spatial scale of observation. The strongest correlation between the MERIS and DAIS NDVI is obtained when using a linear model with an oVset of 0.15 (r=0.31). A Pearson correlation matrix between AGB measured in the eld and each spectral band reveals a modest but signicant ( p
