Table 3 The suggestion for drifiting based on derivative value.
Conditions | The first derivative(FD) | The second derivative(SD) | Suggestion for drifiting |
|---|---|---|---|
① | FD < 0 | SD > 0 | Increasing downward dip |
② | FD < 0 | SD < 0 | Decreasing downward dip |
③ | FD = 0 | SD > 0 | Changing drifiting vertically(upward) |
④ | FD = 0 | SD < 0 | Changing drifiting vertically(downward) |
⑤ | FD > 0 | SD > 0 | Increasing upward dip |
⑥ | FD > 0 | SD < 0 | Decreasing upward dip |
