A GIS-based reassessment of the cartographic accuracy of the <i>Huang Yu Quan Lan Tu</i> and the <i>Nei Fu Yu Tu</i>

This study systematically evaluates the cartographic accuracy of the Qing Dynasty’s Huang Yu Quan Lan Tu (Kangxi Map) and Nei Fu Yu Tu (Qianlong Map), using 26 lakes in the southern Mongolian Plateau as natural references. Historical map sheets first undergo auxiliary geometric correction and georeferencing to a modern framework. Lake features are then digitized, centroids extracted, and spatial distances calculated under the Albers equal-area projection. Lake centroid errors are quantified via MAE/RMSE (decomposed into longitudinal/latitudinal components); residuals are visualized with MapAnalyst-generated distortion grids, and 150 km Tissot’s indicatrices (Sanson/Albers projections) isolate projection effects. The Kangxi Map has higher overall accuracy (MAE = 42.77 km, RMSE = 57.04 km) and stable latitude control (RMSE = 0.283°). The Qianlong Map improves longitudinally near 116.38°E (MAE = 0.343°) but has larger total errors (MAE = 50.78 km, RMSE = 64.41 km) and ‘east-high-west-low’ distortion. Notably, 77% of corresponding lake centroids have < 5 km displacement, confirming the Qianlong Map inherited the Kangxi Map’s core framework. Errors stem from Qing survey limitations, Sanson projection anisotropy, and sheet assembly deviations.This study provides a reproducible method for digitized historical map accuracy evaluation and reveals East Asia’s cartographic transition to evidence-based practice.