The results of these tests and TEMP threshold values are shown in Table 7. These results 

 show that the BP&CL met or exceeded all of the detection distance thresholds specified in the 

 TEMP. 



During these tests, it was observed that a slight swinging of the probe produced detection 

 ranges that were greater than those possible with the probe hanging still over the target. With 

 the probe hanging still over the target, increasing signal strength is indicated by an increase in 

 the deflection of the indicator needle. As the probe is moved over the object, the indicator 

 needle swings from one polarity to the other. The motion of the indicator needle swinging from 

 one polarity to the other provides a better indication of the presence of the object than a slowly 

 increasing needle deflection. 



In performing these tests, the accuracy of locating the position of the target was also 

 evaluated. The TEMP specifies an accuracy of 1 foot or the depth of burial, whichever is 

 greater. Because the indicator needle swings from one polarity to the other as the midpoint of 

 the object is crossed, the accuracy of locating the target is very good. Based on these tests, the 

 accuracy of locating the target is estimated to be within the TEMP specifications. 



Ocean Tests. The objectives of the ocean tests were to verify the operational 

 performance of the system and to identify any safety or human factor deficiencies. These tests 

 were conducted offshore Port Hueneme, California, with dive support provided by the NCEL 

 dive locker. 



To verify the operational performance of the system, both the dipping mode and diver- 

 held mode of operation were tested from an inflatable boat. Prior to beginning the test, a 7-foot 

 length of SD List 5 cable and a 6-foot length of 3/4-inch chain were positioned on the ocean 

 floor in approximately 35 feet of water. The chain was stretched out in a line to produce a line 

 source target (as opposed to a point source for a pile of chain). The relative positions of the tar- 

 gets were recorded using visual sightings. 



To verify the operational performance of the system in the dipping mode, the system was 

 assembled for operation in the inflatable boat (at the test site) and suspended in the water column 

 while the boat performed a slow speed grid pattern search. The probe was positioned about 3 

 feet off the seafloor during this search by periodically lowering it to get slack and then reeling 

 in 3 feet of cable. To aid in towing the probe, a 2-pound brass weight was attached to the end 

 of the probe. 



While executing this search pattern, both the cable and the chain were located with a 

 sensitivity setting of 10 gammas. In both cases, the meter polarity was observed to change as 

 the probe passed over the target. 



To verify the location of the target, the system was converted on site (in the inflatable) 

 to the diver operation mode and used by the divers to pinpoint and provide positive identification 

 of the target. To locate objects on the seafloor, the divers were given about 1/2 hour of 

 instruction prior to the operation. Locating objects in the diver operation mode requires the diver 

 to conduct an iterative procedure of rotating 360 degrees (with the probe extended outward), 

 observing the direction of the largest magnetic signature, and following the direction of the 

 largest magnetic signature until he finds the object or travels 20 to 30 feet. Using this technique, 

 both divers were readily able to find both targets in water with visibility of about 5 feet. In one 

 case, the diver reported that he walked right by the target without seeing it but observed that he 

 passed it by the change in the meter polarity. 



After completing the above tests, the operators were asked to complete a human factors 

 evaluation form on the system. In general, the tool qualities were judged to be suitable for use 



22 



