An integrated declassification and compilation algorithm for public 1:10 000 topographic maps

Abstract

To meet public demand for geospatial products while protecting sensitive geographic information, this paper proposes an integrated declassification and compilation algorithm for public 1:10 000 topographic maps. The method preserves the original compilation logic of public topographic-map production and formalizes it as a reproducible algorithmic workflow. It includes demand analysis, regulatory rule modeling, sensitive feature and attribute filtering, nonlinear planar coordinate declassification with bivariate polynomials, vertical declassification using a unified 30 m contour interval, cartographic representation redesign, and product verification. Four representative map sheets covering flat, hilly, mountainous and alpine terrain were selected for testing. The mean square errors of transformed horizontal positions were 17.76 m, 22.36 m, 26.19 m and 26.67 m, respectively. Feature statistics show that most public-service framework information, including hydrography, transportation, settlements, boundaries, vegetation and geographic names, was retained, while survey control points, spot elevations, sensitive facilities and confidential attributes were removed or generalized. Batch-processing tests on three 16-sheet regional datasets further showed that the proposed workflow completed processing within 2–4 min under different feature-density conditions. The results indicate that the proposed algorithm can produce compliant, usable, efficient and reproducible public topographic-map products from classified large-scale geographic information data.