Sparse Annotation, Dense Supervision: Unleashing Self-Training Power for Occupancy Prediction With 2D Labels. - Zhao jiang Liu; Zhipeng Zhang; Qiang Meng; Yishu Wang 012; Dianmin Zhang; Liujiang Yan; Ke Wang 021; Zhonglong Zheng; Jie Yang 002; Wei Liu 044 (IEEE Robotics Autom. Lett., 2026)