Teledyne 440, System Manual, Page: 130 / 256

6 – Operating Procedure
6-26 © Teledyne TSS DPN 402196 Issue 4.1
part of the target. The SDC compensates for the thickness of any weight coating
and outputs the corrected value. See Figures 6-3 and 6-4.
6. When used, coil altitude (ALT) information comes from an altimeter and is output in millime-
tres. Otherwise, the information in this field will be the fixed coil height if available. The field will
contain ‘????’ if there is no fixed height or altimeter information available.
7. The SDC calculates the target depth of cover (COV) using COV = VRT – ALT in millimetres. A
positive value indicates the target is covered. Zero or negative values indicate an exposed tar-
get. There are several conditions that will cause the field to contain ‘????’:
❐ The target is out of range
❐ The 440 System cannot compute an accurate position for the target
❐ Coil saturation has occurred
❐ There is no fixed coil height or information available to the SDC from an altimeter
8. The signal strengths, in microvolts (µV) measured on Starboard coil, Centre coil, Port coil)
9. This fixed data of ‘+00000’ represents the redundant channel.
10. The QC check code provides additional status information that explains any occurrence of the
QC flag being set. The code consists of a two-digit number with the meaning defined in Table
6-3 . Where possible, the third coil is used to assist the lateral offset calculation. This makes the
LAT more stable and can make the VRT more accurate. For this reason, the most accurate
survey information is available when all three coils are in range. This is indicated by codes 00
and 20.
Table 6-3: QC check code meaning - External logging format
QC
Check
Code
Meaning
00 Lateral offset of target is <±0.9m using port, centre and starboard coils for calculation.
01 Lateral offset of target is <±0.9m using port and starboard coils for calculation.
02 Lateral offset of target is <±0.9m using port and centre coils for calculation.
03 Lateral offset of target is <±0.9m using starboard and centre coils for calculation.
20 Lateral offset of target is >±0.9m using port, centre and starboard coils for calculation. Quality flag is
SET.
21 Lateral offset of target is >±0.9m using port and starboard coils for calculation. Quality flag is SET.
22 Lateral offset of target is >±0.9m using centre and port coils for calculation. Quality flag is SET.
23 Lateral offset of target is >±0.9m using centre and starboard coils for calculation. Quality flag is SET.
30 Saturation of 1 or more coils. Quality flag is SET.
99 Target out of range or Left/Right Tracking. Quality flag is SET.