MonoPP: Metric-Scaled Self-Supervised Monocular Depth Estimation by Planar-Parallax Geometry in Automotive Applications

Gasser Elazab, Torben Gräber, Michael Unterreiner, Olaf Hellwich; Proceedings of the Winter Conference on Applications of Computer Vision (WACV), 2025, pp. 2777-2787

Self-supervised monocular depth estimation (MDE) has gained popularity for obtaining depth predictions directly from videos. However these methods often produce scale-invariant results unless additional training signals are provided. Addressing this challenge we introduce a novel self-supervised metric-scaled MDE model that requires only monocular video data and the camera's mounting position both of which are readily available in modern vehicles. Our approach leverages planar-parallax geometry to reconstruct scene structure. The full pipeline consists of three main networks a multi-frame network a single-frame network and a pose network. The multi-frame network processes sequential frames to estimate the structure of the static scene using planar-parallax geometry and the camera mounting position. Based on this reconstruction it acts as a teacher distilling knowledge such as scale information masked drivable area metric-scale depth for the static scene and dynamic object mask to the single-frame network. It also aids the pose network in predicting a metric-scaled relative pose between two subsequent images. Our method achieved state-of-the-art results for the driving benchmark KITTI for metric-scaled depth prediction. Notably it is one of the first methods to produce self-supervised metric-scaled depth prediction for the challenging Cityscapes dataset demonstrating its effectiveness and versatility. Project page: https://mono-pp.github.io/