INVESTIGATION OF THE MAXIMUM NORMALIZED DIFFERENCE VEGETATION INDEX (NDVI) AND THE MAXIMUM SURFACE-TEMPERATURE (T-S) AVHRR COMPOSITING PROCEDURES FOR THE EXTRACTION OF NDVI AND T-S OVER FOREST

An investigation into the impact of the maximum Normalized Difference Vegetation Index (NDVI) and the maximum surface temperature (T-s) comp ositing procedures (MaN and MaT respectively) upon retrieved NDVI and T-s values extracted from forested areas located across eight months o f cloud-screened European AVHRR data is described. NDVI values are fou nd to be significantly higher and generally less variable when they ar e extracted from MaN rather than from MaT composites and T-s values ar e found to be significantly higher and generally less variable when th ey are extracted from MaT rather than from MaN composites. The impact of these differences is illustrated within the context of a European f orest/non-forest classification that uses both NDVI and T-s data. High er potential forest/non-forest classification accuracies are found usi ng NDVI data extracted from the MaN composites and T-s data extracted from the MaT composites than from any other combination of composited data. The findings indicate that inappropriate selection of a composit ing procedure may have a significant impact upon the subsequent applic ation of NDVI and/or T-s data.