TABLE 1.

List of abbreviations used in this article.

Abbreviation	Explanation	Abbreviation	Explanation
V-SLAM	Visual simultaneous localization and mapping	LSD	Large-scale direct
ROS	Robot Operating System	OKVIS	Open keyframe-based visual–inertial
Lidar	Light detection and ranging	DVO	Dense visual odometry
BA	Bundle adjustment	RPGO	Robust pose-graph optimization
BoW	Bag of words	IMU	Inertial measurement unit
PTAM	Parallel tracking and mapping	GPS	Global positioning system
FAST	Features from accelerated segment test	MAV	Micro air vehicle
ROVIO	Robust visual–inertial odometry	AGV	Automated-guided vehicle
HRI	Human–robot interaction	UAV	Unmanned aerial vehicle
DTAM	Dense tracking and mapping	AR	Augmented reality
LCP	Loop closure process	VR	Virtual reality
SS	Semantic segmentation	RoLi	Range of light intensity
DSt	Dense stereo	ILR	Illumination and light robustness
DSe	Dense semantics	BRIEF	Binary Robust Independent Elementary Features
SCE	Spatial coordinate errors