| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | at an [noun] | 1398 |
|
| 2 | at an [noun sg] | 1270 |
|
| 3 | [prep] an altitude | 54 |
|
| 4 | at [art] altitude | 40 |
|
| 5 | at [art] altitude | 40 |
|
| 6 | at a altitude | 39 |
|
| 7 | at an altitude | 39 |
|
