Lake Maggiore - Italy, 3-6 April 2000
VEGETATION/SPOT for Northern Applications: Assessment of Utility and Examples of Products
Chen and Josef Cihlar
10-day Canada-wide synthesis images of VEGETATION acquired in the growing season (April 1 to November 30) in 1998 have been assessed for northern applications. The images received from the VITO centre after atmospheric corrections have been normalized to a common illumination and observation geometry (45° solar zenith angle and nadir view) after an angular correction procedure. Radiometry and atmospheric correction have been analysed using a dense dark vegetation inversion. Pixels contaminated by subpixel clouds were detected and replaced through temporal interpolation. The corrected images have been used for various applications including landcover classification, leaf area index (LAI) retrieval, fire scar area and age estimation, and net primary productivity (NPP) modelling. The utility of the VEGETATION sensor is assessed in comparison with AVHRR and Landsat TM sensors, with emphasis on the usefulness of the shortwave infrared (SWIR) channel. It is found that SWIR reflectance is very useful for improving landcover classification. SWIR information can also be used to suppress the background (understory, litter and moss) effects on forest LAI retrieval. These improvements in landcover and LAI mapping using VEGETATION images are significant in pixel-based NPP modelling. Mapping of new fire scar areas is also improved with the use of the SWIR band. The ratio of SWIR to near-infrared (NIR) reflectance was found to be highly correlated to fire scar age up to 50 years. This ability of mapping fire scar age is critical in estimating the spatial distribution of carbon sources and sinks in the northern ecosystems as the age determines the amounts of regrowth and heterotrophic respiration.