The horizontal shift was skewed towards the western and north-western directions, indicative of systematic error. The most recent GE imagery (year 2018) had the least horizontal error while year 2000 had the largest horizontal error.
A novel approach for assessing the space–time variations in the magnitude and direction of errors in GE imagery is presented. Two readily available 30-m digital elevation models (DEMs) - the Shuttle Radar Topography Mission (SRTM) v3.0 and the Advanced Land Observing Satellite World 3D (AW3D) DEM v2.1. The horizontal accuracy of historical Google Earth (GE) images at four epochs between the years 20, and the vertical accuracy of its elevation data within Lagos State, in Nigeria, are respectively evaluated by comparison with a very high–resolution digital orthomosaic and comparison with 558 ground control points.
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