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USE OF GAC DATA FOR MONITORING THE CANADIAN LANDMASS 
M.A D’lorio (1), J. Cihlar (1), and D W Mullins (2) 
(1) Canada Centre For Remote Sensing 
1547 Merivale Road 
Nepean, Ontario, K1A 0Y7 
TEL: (613) 952-0500 
FAX: (613) 952-7353 
(2) Intera Renting 
1525 Carling Avenue 
Ottawa, Ontario, K1Z 8R9 
TEL: (613) 728-6111 
FAX: (613) 728-4009 
ABSTRACT 
One of the difficulties associated with monitoring global vegetation using satellite data is the need for both good 
temporal and spatial coverage. The Canada Centre for Remote Sensing (CCRS), through its Global Change 
Program, has been evaluating the use of data from the Advanced Very High Resolution Radiometer (AVHRR) 
on board the National Oceanic and Atmospheric Administration (NOAA) satellite. 
Composites of North American data at Global Area Coverage (GAC) were obtained from NASA through a 
cooperative project These data have a nominal resolution of 4 km and had been calibrated using pre-launch 
sensor values. The study period chosen was from 1982 to 1986 inclusive. 
The purpose of the study was to evaluate annual variations in the seasonal profiles of the Normalized 
Difference Vegetation Index (NDVI) for areas of different landuse. The primary landcover types were selected 
from a map of ecological regions, or ecodistricts, obtained from Environment Canada. The seasonal profiles 
displayed yearly shifts in the response of the NDVI to changing environmental conditions such as drought The 
variations in seasonal NDVI profiles illustrate both yearly phenomena and more generalized trends in 
vegetation growth patterns.