Mapping and monitoring small stakholder agriculture in Tigray, Ethiopia using sub-meter Worldview and Landsat imagery and high performance computing.

Abstract

Very high resolution (VHR) satellite data is experiencing rapid annual growth, producing petabytes of remotely sensed data per year. The WorldView constellation, operated by DigitalGlobe, images over 1.2 billion km2 annually at a \u3e 2 m spatial resolution. Due to computation, data cost, and methodological concerns, VHR satellite data has mainly been used to produce needed geospatial information for site-specific phenomenon. This project produced a VHR spatiotemporally-explicit wall-to-wall cropland area map for the rainfed residential cropland mosaic of Tigray Region, Ethiopia, which is comprised entirely of smallholder farms. Moderate resolution satellite data is not adequate in spatial or temporal resolution to capture total area occupied by smallholder farms, i.e., farms with agricultural fields of ≥ 45 × 45 m in dimension. In order to accurately map smallholder crop area over a large region, hundreds of VHR images spanning two or more years are needed. Sub-meter WorldView-1 and WorldView-2 segmentation results were combined median phenology amplitude from Landsat 8 data. VHR WorldView-1, -2 data were obtained from the U.S. National Geospatial-Intelligence Agency (NGA) Commercial Archive Data at NASA Goddard Space Flight Center (GSFC) (http://cad4nasa.gsfc.nasa.gov/). Over 2700 scenes were processed from raw imagery to completed crop map in 1 week in a semi-automated method using the large computing capacity of the Advanced Data Analytics Platform (ADAPT) at NASA GSFC\u27s NCCS (http://www.nccs.nasa.gov/services/adapt). This methodology is extensible to any land cover type and can easily be expanded to run on much larger regions