 The advancements in remote sensing technology have led to the production of multiple global land cover maps over the past decade. These maps provide valuable information about the Earth's surface, but they can be difficult to use due to their inconsistent classifications and lack of validation methods. In order to better understand the limitations of these maps, this study compared and analyzed the four global land cover mapping projects, IGBP Discover, UMD Land Cover, Global Land Cover 2000, and Glob Cover 2009. The authors found that the classification schemes were inconsistent and that the validation methods varied significantly among the projects. Additionally, the authors identified the most significant errors and uncertainties in each project and suggested improvements for future global land cover mapping efforts. This article was authored by Russell Jeetso-Lalton, Jinyugu, Kaminiyatov, and others.