Table 2.
Accuracy assessment of weed detection as affected by camera (vegetation index), date (phenological stage) and flight altitude. In columns, percentage of ground-truth frames correctly and incorrectly classified (see Section 2.4 and Figure 4).
| Flight date (Phenological Stage) | Weed Presence | Flight Altitude (m) | Camera (Vegetation Index) | |||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Visible-Light (ExG) | Multispectral (NDVI) | |||||||||
| Correct (%) | Under-Estimated (%) | False − (%) | False + (%) | Correct (%) | Under-estimated (%) | False − (%) | False + (%) | |||
| Date 1–44 DAS (4 true leaves) | Weed | 40 | 71 | 5 | 14 | 10 | 71 | 10 | 19 | - |
| 60 | 43 | 10 | 43 | 4 | 62 | 10 | 28 | - | ||
| 80 | 29 | 10 | 48 | 13 | 57 | 10 | 33 | - | ||
| 100 | 19 | 10 | 24 | 47 | 43 | 14 | 29 | 14 | ||
| No weed | 40 | 100 | - | - | - | 100 | - | - | - | |
| 60 | 100 | - | - | - | 100 | - | - | - | ||
| 80 | 44 | - | - | 56 | 100 | - | - | - | ||
| 100 | 33 | - | - | 67 | 100 | - | - | - | ||
| Date 2–50 DAS (5–6 true leaves) | Weed | 40 | 77 | 5 | 14 | 4 | 91 | 9 | - | - |
| 60 | 64 | 18 | 14 | 4 | 62 | 19 | 19 | - | ||
| 80 | 45 | 14 | 27 | 14 | 55 | 9 | 36 | - | ||
| 100 | 45 | 5 | 9 | 41 | 50 | 14 | 27 | 9 | ||
| No weed | 40 | 88 | - | - | 12 | 100 | - | - | - | |
| 60 | 88 | - | - | 12 | 100 | - | - | - | ||
| 80 | 63 | - | - | 37 | 100 | - | - | - | ||
| 100 | 37 | - | - | 63 | 88 | - | - | 12 | ||
| Date 3–57 DAS (7–8 true leaves) | Weed | 40 | 68 | 14 | 18 | - | 60 | 7 | 33 | - |
| 60 | 68 | 14 | 18 | - | 50 | 9 | 36 | 5 | ||
| 80 | 50 | - | 14 | 36 | 41 | 9 | 36 | 14 | ||
| 100 | 27 | - | 41 | 32 | 41 | - | 45 | 14 | ||
| No weed | 40 | 88 | - | - | 12 | 100 | - | - | - | |
| 60 | 100 | - | - | - | 88 | - | - | 12 | ||
| 80 | 63 | - | - | 37 | 88 | - | - | 12 | ||
| 100 | 63 | - | - | 37 | 100 | - | - | - | ||