Beyond Platform Type: Effects of Vegetation Density, Sensor Modality, and Search Strategy on Aerial Search and Rescue Performance

Authors

Andreas A. Nilsen
Tale R. Størdal
Vegard Johansen
Jørgen L.H. Ronge
Eyvind Grytting

Abstract

Timely detection of missing persons is critical for successful Search and Rescue (SAR) operations, especially under challenging environmental conditions. Modern SAR efforts utilize both manned helicopters and unmanned aerial systems (UAS), often equipped with electro-optical (EO) and infrared (IR) sensors, while helicopters may also employ visual observers. Despite their widespread use, limited empirical data exists on how these platforms, sensor types, and search techniques perform across varying terrain and vegetation densities. To our knowledge, no prior field study has jointly examined how platform type, sensor modality, search strategy, and vegetation density affect detection performance in realistic SAR conditions. This study presents results from the SAVIOUR 2024 quasi-experimental field experiment, conducted during a large-scale SAR exercise in Rogaland, Norway. Twelve professional SAR aircrews (six helicopters, six UAS teams) conducted 48 search sorties across sectors with low, medium, and high vegetation density, targeting 251 human subjects. Key metrics were Probability of Detection (POD) and Time to Detection. Both platforms achieved high detection rates (mean POD >83%), with 54% of sorties reaching 100% POD. Vegetation density was the strongest predictor of POD, with reduced performance in high-density forest (helicopters: 71.4%, UAS: 73.3%). Platform type was not a significant predictor of POD when controlling for vegetation density; in contrast, vegetation density and sensor modality seemed to have stronger effects on detection performance. Helicopters detected targets faster, likely due to initial sweep strategies. UAS teams favored systematic detailed searches, resulting in longer detection intervals. Sensor-based searches outperformed visual-only methods, though visual-only data were limited. As an operational implication, we suggest that coordinated, vertically separated operations - helicopters at high altitude and UAS at low altitude - may enhance efficiency through concurrent coverage. However, this coordination model was not directly tested as an intervention and should be validated in future studies. These findings offer guidance for integrated SAR practices and highlight future research needs, including AI-assisted detection and performance evaluation under diverse thermal and geographical conditions.

Keywords: Search and Rescue (SAR); Unmanned Aerial Systems (UAS); helicopter; probability of detection (POD); comparative analysis; airspace management; synergistic aerial operations

Publication details

International Journal of Disaster Risk Management (IJDRM), Vol. 8, No. 1 (2026), pp. 511-538.

DOI: https://doi.org/10.66050/sja2vn07

Read the full open-access article:
https://internationaljournalofdisasterriskmanagement.com/index.php/Vol1/article/view/234

Download PDF:
https://internationaljournalofdisasterriskmanagement.com/index.php/Vol1/article/view/234/231

Suggested citation

Nilsen, A. A., Størdal, T. R., Johansen, V., Ronge, J. L., & Grytting, E. (2026). Beyond Platform Type: Effects of Vegetation Density, Sensor Modality, and Search Strategy on Aerial Search and Rescue Performance. International Journal of Disaster Risk Management, 8(1), 511-538. https://doi.org/10.66050/sja2vn07