Ontology-based prompting with large language models for inferring construction activities from construction images

Recognizing construction activities from images enhances decision-making by providing context-aware insights into project progress, resource allocation, and productivity. However, conventional approaches, such as supervised learning and knowledge-based approach, struggle to generalize to the dynamic nature of construction sites due to limited annotated data and rigid knowledge patterns. To address these limitations, we propose a novel method that integrates Large Language Models (LLMs) with structured domain knowledge via ontology-based prompting. In our approach, visual features such as entities, spatial arrangements, and actions are mapped to predefined concepts in a construction-specific ontology, resulting in symbolic scene representations. In-context learning is employed by constructing prompts that include multiple structured examples, each describing a scenario with its associated activities. By analyzing these ontology-grounded examples, the LLM learns patterns that connect symbolic representations to construction activity labels, enabling generalization to new, unseen scenes. We evaluated the method using GPT-based models on a dataset covering 29 construction activity types. The model achieved an activity recognition accuracy of 73.68 %, and 50.00 % when jointly identifying the activity and its associated entities. Ablation studies confirmed the positive effects of including Chain-of-Thought reasoning, diverse visual concepts, and richer context examples. These results demonstrate the potential of ontology-informed prompting to support scalable and adaptive visual understanding in construction domains.