Spatial and temporal changes in household structure locations using high-resolution satellite imagery for population assessment: an analysis of household locations in southern Zambia between 2006 and 2011

摘要

Satellite imagery is increasingly available at high spatial resolution and can be used for various purposes in public health research and program implementation. Comparing a census generated from two satellite images of the same region in rural southern Zambia obtained four and a half years apart identified patterns of household locations and change over time. The length of time that a satellite image-based census is accurate determines its utility. Households were enumerated manually from satellite images obtained in 2006 and 2011 of the same area. Spatial statistics were used to describe clustering, cluster detection, and spatial variation in the location of households. A total of 3,821 household locations were enumerated in 2006 and 4,256 in 2011, a net change of 435 houses (11.4% increase). Comparison of the images indicated that 971 (25.4%) structures were added and 536 (14.0%) removed. Further analysis suggested similar household clustering in the two images and no substantial difference in concentration of households across the study area. Cluster detection analysis identified a small area where significantly more household structures were removed than expected; however, the amount of change was of limited practical significance. These findings suggest that random sampling of households for study participation would not induce geographic bias if based on a 4.5 year old image in this region. Application of spatial statistical methods provide insights into the population distribution changes between two time periods and can be helpful in assessing the accuracy of satellite imagery.