Research Article
Safety Assessment and Risk Estimation for Unmanned Aerial Vehicles Operating in National Airspace System
Table 1
Different sheltering factors in different areas.
| Type No. | Area | Sheltering factor |
| Type 1 | Reinforced concrete buildings | 40 | Type 2 | Trees | 20 | Type 3 | Sparse trees | 10 | Type 4 | Area without obstacles | 0 |
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