Classification of time series of NDVI for Assessment of land cover change in Ghana using Noaa/A VHRR data.
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Date
April, 2010.
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Abstract
Land cover information constitutes key environmental information for many scientific,
resource management and policy purposes, as well as for a range of human activities. Hence it
has become a major focus for the International Geosphere-Biosphere Program (IGBP) and the
International Human Dimensions Program (IHDP) at global and regional levels. Land cover
information is currently scarce for Ghana. The country is currently undergoing rapid and
wide-range changes in vegetation due to climate change, the practice of slash-and-burn
or shifting cultivation. The stud y of these conversions necessitates the use of remote
sensing because it provides data at synoptic scales and facilitates the discerning of large-
scale ecosystem patterns. Although remote sensing technology has been used for mapping in
Ghana for sometime now, there has been no attempt to use either unsupervised or supervised
classification methods for NOAA/AVHRR images for the whole of Ghana. Therefore a
qualitative approach to the use of historical series of low resolution NDVI data to produce land
cover maps of Ghana and also to evaluate the relative change in land cover from
1982 to 2002 has been developed. The study was carried out through the principal
component analysis and classification of long term average NDVI values. The interpretation of
the resulting classes was based on the comparison between NDVI average temporal profiles of
different classes and NDVI reference profiles for selected sites where detailed
information about vegetation characteristics are available. The results show the potential of
the proposed approach for studies at regional or national level where lack of climate data
hinder the utilization of quantitative methods to determine the land cover change within the
periods (1982-1992, 1992-2002 and 1982-2002). Again the results of the study shows that the
dominant land coverchange process was conversion of natural vegetation to savannah and
shrub thicket, which occurred at an annual rate of 4% and 6.5% respectively. Most of the
land cover change process occurred in the first period (1982-1992).
The overall annual rate of change in land cover (1982-1992) was highest for Savannah
(3.8%) and lowest for water (1.03%).
The results suggest that, year phenological behavior, as revealed by the NDVI data, can be
used to map general patterns in the spatial distribution of Ghana‟s main vegetation formation.
Description
A these submitted to the Department of Geomantic Engineering,
Kwame Nkrumah University of Science and Technology in partial fulfillment of the requirements for the degree of Master of Science.