Multi-Scale Hierarchical CRF for Railway Electrification Asset Classification From Mobile Laser Scanning Data

A network of railway infrastructure is one of the most critical infrastructure assets for supporting the national economy and sustainable mobility. Safe and reliable maintenance of railway infrastructure is critical to ensure that rail systems run safely and punctually. Such maintenance requires regular surveying of railway assets, which typically relies on time-consuming and error-prone labor-centric visual inspection. In this paper, we propose a novel supervised method for automatically classifying electrification assets of railway networks using mobile laser scanning data. A hierarchical Conditional Random Field (CRF) was investigated in order to apply both smoothness constraint and spatial regularities, to improve the classification result made by local supervised classifiers. We use a multi-scale line representation of original data, which implicitly combines object geometry cues and makes computation efficient. Our approach focuses on learning the spatial regularities at multiple representation scales to thoroughly understand the railway electrification scene. The spatial regularities are formulated as relative spatial location in a middle range for different line primitive scales and relative displacement in a full range for the final coarsest line primitive scale. The experiment shows that learnt spatial regularities at full range with multi-scales can outperform the model with spatial regularities at limited local ranges.