outside-in tracking:  SLAM (simultaneous localization and mapping)

SLAM:  Simultaneous localization and mapping

ORB-SLAM2

an Open-Source SLAM System for Monocular, Stereo and RGB-D Cameras on GitHub

PLVS:  Points, Lines, Volumetric mapping, and Segmentation

a real-time system that leverages sparse SLAM, volumetric mapping, and 3D unsupervised incremental segmentation
PLVS II also supports IMUs (intertial measurement units>