Evaluating the relationship between Modis and AVHRR vegetation indices
Date
2006-11-14T13:54:24Z
Authors
Malherbe, Johan
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Abstract
This report deals with the relationship between the NDVI obtained from the NOAA
AVHRR sensor and that obtained from the MODIS sensor. The relationship is
quantitatively assessed for distinct polygons over various land-cover types in the
northeastern Kwa-Zulu Natal Province of South Africa. Spatial and temporal variations in
the relationships are addressed and discussed with reference to spectral response, sunsensor-
target geometries and atmospheric factors.
Specifically, various methods are investigated to estimate a MODIS-equivalent NDVI
from the AVHRR NDVI and in so doing create the potential to develop a self-consistent
NDVI between the historically available AVHRR NDVI dataset and the relatively new
MODIS NDVI dataset. NOAA-16 AVHRR NDVI data and AQUA MODIS NDVI data for
the two-year period from January 2002 to December 2003 are used to develop the method.
A linear relationship exists between the AVHRR and MODIS NDVI. However, spatial
variations in the relationship in terms of land-cover and mean NDVI are pointed out. The
potential of atmospheric corrections applied to AVHRR data through a radiative transfer
atmospheric correction model to improve the relationship between the two NDVI datasets
is also investigated.
The importance of geo-location accuracy of the AVHRR NDVI dataset is assessed in the
light of the accuracy obtainable with the proposed method to estimate a MODIS-equivalent
NDVI from the AVHRR NDVI.
A method to estimate the MODIS NDVI from the AVHRR NDVI that takes the mean
AVHRR NDVI value into account, as opposed to a constant linear relationship over all the
points, is proposed. Atmospheric correction is shown not to improve the accuracy of the
method in a statistically significant way. The root-mean-square error of the proposed
method is in the order of 0.05 NDVI units and varies between 0.5 and 2 standard
deviations of the MODIS NDVI over an entire season.
Description
Student Number : 0216831W -
MSc research report -
School of Environmental Sciences -
Faculty of Science
Keywords
MODIS, AVHRR, normalized difference vegetation index, NDVI, atmospheric correction