Table 2 Detected anomalies by depth and ERF threshold.
Depth | Section 1 | Section 2 | Section 3 | Section 4 | ||||
|---|---|---|---|---|---|---|---|---|
Internal | External | Internal | External | Internal | External | Internal | External | |
80% and above | – | – | – | – | – | – | – | – |
70% ≤ metal loss < 80% | – | – | – | – | – | – | – | – |
60% ≤ metal loss < 70% | – | – | – | – | – | – | – | – |
50% ≤ metal loss < 60% | – | – | – | 2 | – | – | – | – |
40% ≤ metal loss < 50% | – | – | – | – | – | – | – | – |
30% ≤ metal loss < 40% | 14 | – | 1 | – | 4 | – | – | – |
20% ≤ metal loss < 30% | 233 | 2 | 31 | 3 | 10 | – | 10 | – |
10% ≤ metal loss < 20% | 4988 | 169 | 4092 | 323 | 987 | 265 | 203 | 21 |
Total no. of anomalies | 5235 | 171 | 4124 | 328 | 1001 | 265 | 213 | 21 |
ERF | ||||||||
 ERF < 0.6 | 105 | 2 | – | – | 6 | 0 | 40 | – |
 0.6 ≤ ERF < 0.8 | 5130 | 169 | 1127 | 57 | 213 | 65 | 173 | 21 |
 0.8 ≤ ERF < 1.0 | – | – | 2997 | 271 | 782 | 200 | – | – |
 ERF > 1.0 | – | – | – | – | – | – | – | – |
Total no. of anomalies | 5235 | 171 | 4124 | 328 | 1001 | 265 | 213 | 21 |
