| Aerodynamic roughness length(m) | Classification | Landscape |
| 0.0002 | sea | sea, paved areas, snow-covered flat plain, tide flat, smooth desert |
| 0.005 | smooth | beaches, pack ice, morass, snow-covered fields |
| 0.03 | open | grass prarie or farm fields, tundra, airports, heather |
| 0.1 | roughly open | cultivated area with low crops and occasional obstacles (single bushes) |
| 0.25 | rough | high crops, crops of varied height, scattered obstacles such as trees or hedgerows, vineyards |
| 0.5 | very rough | mixed farm fields and forest clumps, orchards, scattered buildings |
| 1.0 | closed | regular coverage with large size obstacles with open spaces roughly equal to obstacle heights, suburban houses, villages, natural forests |
| Greater than or equal to 2 | chaotic | centers of large towns and cities, irregular forests with scattered clearings |