Monocular Visual Teach and Repeat Aided by Local Ground Planarity

TL;DR

This paper presents a monocular vision system for high-accuracy route repetition in autonomous vehicles by leveraging ground planarity assumptions to recover absolute scale, enabling centimetre-level accuracy over long distances without additional sensors.

Contribution

It introduces a monocular visual Teach and Repeat system that estimates absolute scale using ground planarity, allowing kilometre-scale route repetition with high accuracy.

Findings

Achieves centimetre-level accuracy over 4.3 km

Performs comparably to stereo-based systems in non-planar terrain

Enables high-precision autonomous navigation with only monocular cameras

Abstract

Visual Teach and Repeat (VT\&R) allows an autonomous vehicle to repeat a previously traversed route without a global positioning system. Existing implementations of VT\&R typically rely on 3D sensors such as stereo cameras for mapping and localization, but many mobile robots are equipped with only 2D monocular vision for tasks such as teleoperated bomb disposal. While simultaneous localization and mapping (SLAM) algorithms exist that can recover 3D structure and motion from monocular images, the scale ambiguity inherent in these methods complicates the estimation and control of lateral path-tracking error, which is essential for achieving high-accuracy path following. In this paper, we propose a monocular vision pipeline that enables kilometre-scale route repetition with centimetre-level accuracy by approximating the ground surface near the vehicle as planar (with some uncertainty) and recovering absolute scale from the known position and orientation of the camera relative to the vehicle. This system provides added value to many existing robots by allowing for high-accuracy autonomous route repetition with a simple software upgrade and no additional sensors. We validate our system over 4.3 km of autonomous navigation and demonstrate accuracy on par with the conventional stereo pipeline, even in highly non-planar terrain.