Sparse-Reference Satellite Monitoring of Extraction and Agricultural Reclamation in Small-Scale Borrow-Pit Mining

Small borrow pits in agricultural landscapes are difficult to monitor because exposed mining surfaces resemble bare cropland, extraction is intermittent, and production records are often limited. This study characterized borrow materials in Indramayu, Indonesia, developed a sparse-reference satellite workflow to reconstruct mining-opening dynamics, and evaluated post-extraction agricultural reuse. Thirty-two PlanetScope SuperDove acquisitions from 2020 to 2026 were analyzed using five expert delineations for training, spatial constraint, and selection of a single scene-independent Random Forest threshold. Two reference-derived reliability screens, based on commission over presumed non-mining farmland and omission of a persistent open core, determined which acquisitions supported area estimation. Ten acquisitions were retained, with temporal gaps reported without interpolation. Mapped openings increased from 3.5 ha in 2020 to 28.0 ha in July 2023, then declined to 15.7 ha in April 2025 and to a single-screen estimate of 5.5 ha in February 2026, within a 47.9 ha minimum mapped footprint. Laboratory characterization showed substantial engineering variability, while a 6.25 ha former opening exhibited declining open-surface fraction and persistent vegetation recovery consistent with agricultural reuse. The results demonstrate the value and limitations of sparse-reference satellite monitoring for small-scale borrow-pit extraction and reclamation.