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How to Compensate for Responder Latency
23 November 2022
This article explains how to compensate for responder latency.
The time between triggering a Responder from topside equipment, and the actual acoustic burst (latency) will cause a positioning error if not compensated.
This shows a normal transponder.
Select the transponder – the Beacon Specific button is not available.
Change to Responder mode.
With an NSH connected, you would normally see the NSH port.
Clicking Apply causes the CS:2709;…..,RSP1 command to be acoustically sent to the beacon (for a WSM6+, for example).
Select the Responder – the Beacon Specific button is now available.
Click the Beacon Specific button.
The following will not send any acoustic command, but instead tell Marksman/Ranger2 to allow for a 30 ms delay from the rising edge of the Responder pulse to the beacon actually transmitting its acoustic pulse.
Click OK to confirm.
In this example, in 1000 m water depth @ 1485 m/s, if the 30 m latency was not accounted for, then straight over the Responder, its depth would indicate 44.55 m deeper than it should be.
Latency can be accurately measured by using an oscilloscope to view the time between the rising edge of the electrical stimulus from topside equipment, to the actual burst of acoustic energy from the transducer.
Alternatively, with an accurate sound speed entered, and the beacon directly below the Transceiver, the beacon can be switched between Transponder and Responder mode, and latency estimated.
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