AcATaMa: A QGIS plugin for accuracy assessment and area estimation

Thematic maps are indispensable for environmental monitoring, resource management, and policy-making, yet their value depends critically on rigorous accuracy assessment. AcATaMa (Accuracy Assessment of Thematic Maps) is a free, open-source QGIS plugin that delivers an integrated workflow for thematic map accuracy assessment and sample-based area estimation, enabling users to follow international good practice guidelines within a single, accessible environment. The plugin integrates three core components: sampling design (simple random, stratified random, and systematic), response design (a multi-window interface for simultaneous review of multiple reference data sources), and analysis (error matrices, accuracy metrics, area-adjusted estimates, and confidence intervals). By unifying these components, AcATaMa addresses a critical gap: no prior open-source tool provides a complete, end-to-end accuracy-assessment workflow within a desktop GIS environment. Its effectiveness is demonstrated through a case study assessing Colombia's National Forest Change Map for 2018–2019. Global adoption, over 160,000 downloads and application in 86 peer-reviewed studies across diverse domains, confirms the tool's broad scientific relevance and societal impact.