Spatial Consistency and Accuracy Assessment of Grassland Classification in the Sanjiangyuan Region: From Six Medium Resolution Land Cover Products

The Sanjiangyuan Region (SJYR), located in the core of the Qinghai–Tibet Plateau, is a key ecological barrier where grasslands, the dominant land cover, are undergoing continuous degradation due to climate change and human activities. Accurate characterization of grassland is essential for ecological monitoring, yet existing land-cover products show substantial discrepancies in alpine environments. This study systematically evaluated the spatial consistency and accuracy of six publicly medium resolution land cover products: GLC_FCS30, GlobeLand30, FROM_GLC10, ESA WorldCover (ESA), ESRI Land Cover (ESRI), and Dynamic World. We evaluated these products by comparing them with the Third National Land Survey data, performing Jaccard similarity and spatial consistency analyses, and validating their accuracy using five metrics: Overall Accuracy (OA), Producer’s Accuracy (PA), User’s Accuracy (UA), F1-score, and Matthews Correlation Coefficient (MCC). Results show large variations in estimated grassland area, ranging from 91,105 km² (Dynamic World) to 325,669 km² (GLC_FCS30). Pixel-level comparison revealed significant spatial heterogeneity, with only 54.3% of the region showing the desired high consistency. Accuracy validation indicated that ESA achieved the best classification results (OA = 74.24%, MCC = 0.80), while Dynamic World performed the worst (OA = 57.45%, F1 = 0.28). These products showed lower consistency in high-altitude western areas, and classification accuracy for most products varied with elevation and slope, indicating that topographic factors significantly influence remote sensing classification capabilities. These results provide a quantitative basis for product selection in the SJYR and highlight the need for improved calibration, data fusion, and classification approaches that better account for sparse vegetation and complex topography.