Recommended citation: Y. Jin, N. Wei, M. Fu, H. Liu and W. -A. Zhang, "Beyond Learning: Back to Geometric Essence of Visual Odometry via Fusion-Based Paradigm," in IEEE Transactions on Instrumentation and Measurement, vol. 70, pp. 1-15, 2021, Art no. 5018715, doi: 10.1109/TIM.2021.3121483.