Masters Theses

Date of Award

5-2015

Degree Type

Thesis

Degree Name

Master of Science

Major

Geography

Major Professor

Nicholas N. Nagle

Committee Members

Liem Tran, Yingkui Li

Abstract

Remote sensing is a valuable source of data for the study of human ecology in rural areas. In this thesis, I attempt to analyze the presence of a long-term trend indicative of post-resettlement adaptation in the vegetation signals of Western Rwanda. There is a dearth of research utilizing medium resolution imagery to study difficult environments, such as tropical-montane regions, where complex topography and cloud cover diminish image accuracy. I attempt to add to the extant literature on frequency-domain smoothing methods as well as the literature on human-environment interaction in tropical-montane regions by applying a harmonic filtering and smoothing algorithm to the ‘MOD13Q1’, 16-day composite, 250m, NDVI, MODIS imagery. To create a more robust time-series, I combine Gaussian generalized additive models and discrete Fourier analysis of the residuals to impute values to a filtered time series, based on MODIS’s own pixel reliability data. These methods significantly improve the quality of the time-series being analyzed, compared with the raw data, or imputation of the mean signal. To control for conflating variables, I take a difference-in-differences (DD) approach (Abadie, 2005) comparing resettled regions to older regions, identified in Google Earth. Harmonic filtering and smoothing shows a definite long-term trend of post-resettlement changes in the vegetation signal, demonstrated by the DD approach, analyzed in SiZer maps (Chaudhuri & Marron, 1999). Further research will be needed to determine whether this is indicative of cropping changes, or other impacts of post-resettlement adaptation.

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