ST-ProC: A Graph-Prototypical Framework for Robust Semi-Supervised Travel Mode Identification

TL;DR

ST-ProC is a graph-prototypical semi-supervised learning framework that effectively improves travel mode identification from GPS data with limited labels by addressing data manifold and noise issues.

Contribution

It introduces a novel graph-prototypical SSL framework with a margin-aware pseudo-labeling strategy for robust semi-supervised travel mode identification.

Findings

Outperforms baselines by 21.5% in accuracy

Effectively handles label scarcity in real-world GPS data

Enhances data representation quality

Abstract

Travel mode identification (TMI) from GPS trajectories is critical for urban intelligence, but is hampered by the high cost of annotation, leading to severe label scarcity. Prevailing semi-supervised learning (SSL) methods are ill-suited for this task, as they suffer from catastrophic confirmation bias and ignore the intrinsic data manifold. We propose ST-ProC, a novel graph-prototypical multi-objective SSL framework to address these limitations. Our framework synergizes a graph-prototypical core with foundational SSL Support. The core exploits the data manifold via graph regularization, prototypical anchoring, and a novel, margin-aware pseudo-labeling strategy to actively reject noise. This core is supported and stabilized by foundational contrastive and teacher-student consistency losses, ensuring high-quality representations and robust optimization. ST-ProC outperforms all baselines by a significant margin, demonstrating its efficacy in real-world sparse-label settings, with a performance boost of 21.5% over state-of-the-art methods like FixMatch.