Sphere-Depth: A Benchmark for Depth Estimation Methods with Varying Spherical Camera Orientations

TL;DR

Sphere-Depth introduces a benchmark for evaluating the robustness of monocular depth estimation models on spherical images under camera pose variations, highlighting performance degradation and providing a standardized evaluation protocol.

Contribution

The paper presents a new benchmark, evaluation protocol, and dataset splits for assessing depth estimation models' robustness to pose variations in spherical images.

Findings

Models degrade significantly under pose perturbations.

Spherical-aware models still face performance drops with pose variations.

A depth calibration protocol improves metric depth evaluation.

Abstract

Reliable depth estimation from spherical images is crucial for 360{\deg} vision in robotic navigation and immersive scene understanding. However, the onboard spherical camera can experience unintentional pose variations in real-world robotic platforms that, along with the geometric distortions inherent in equirectangular projections, significantly impact the effectiveness of depth estimation. To study this issue, a novel public benchmark, called Sphere-Depth, is introduced to systematically evaluate the robustness of monocular depth estimation models from equirectangular images in a reproducible way. Camera pose perturbations are simulated and used to assess the performance of a popular perspective-based model, Depth Anything, and of spherical-aware models such as Depth Anywhere, ACDNet, Bifuse++, and SliceNet. Furthermore, to ensure meaningful evaluation across models, a depth calibration-based error protocol is proposed to convert predicted relative depth values into metric depth values using supervised learned scaling factors for each model. Experiments show that even models explicitly designed to process spherical images exhibit substantial performance degradation when variations in the camera pose are observed with respect to the canonical pose. The full benchmark, evaluation protocol, and dataset splits are made publicly available at: https://github.com/sgazzeh/Sphere_depth