Table of Contents
Deployment
On September 17, 2021, the underwater platform was placed on the Berm near Parrsboro, Nova Scotia during low tide. This day was chosen as it had the lowest tide level during the daytime hours which allowed it to be at the greatest depth during the scheduled sea trial. The platform was placed on the Berm at a tide level of 2.0m (4:27 PM local time) and the following photograph was taken shortly after the deployment (4:53 PM local time):
Sea Trial
On October 1st, 2021, a sea trial was performed using the platform. On this day, high tide occurred at 9:09 AM local time (13:09 UTC) with a tide level of 10.0m, which represents a platform depth of 8.0m. During this trial, several different sound sources were used to test the localization capabilities of the platform. During the 12 individual tests that were performed from 13:48 to 15:26 (UTC), an ADCP (Acoustic Doppler Current Profiler) was used to measure the depth of the platform with depths varying from around 7.5m to 4.5m:
In each of the 12 tests, a variety of different transmitters were used. The following table summarizes the transmitter(s) used throughout the trial:
| Trial # | Transmitter | Start Time (UTC) | End Time (UTC) |
|---|---|---|---|
| 1 | Vessel Echosounder | 13:48 | 13:51 |
| 2 | Vessel Echosounder | 14:04 | 14:11 |
| 3 | icTalk | 14:15 | 14:18 |
| 4 | icTalk | 14:18 | 14:24 |
| 5 | icTalk + Custom @ 20 click/sec | 14:28 | 14:35 |
| 6 | Custom @ 20 click/sec | 14:40 | 14:45 |
| 7 | Custom @ 200 click/sec | 14:47 | 14:48 |
| 8 | Custom @ 200 click/sec | 14:50 | 14:54 |
| 9 | Vessel Echosounder | 14:56 | 15:01 |
| 10 | Custom @ 20 click/sec | 15:06 | 15:11 |
| 11 | icTalk + Vessel Echosounder | 15:17 | 15:20 |
| 12 | Vessel Echosounder | 15:22 | 15:26 |
Another crucial parameter that was measured was the sound speed in the water column which was measured using the ADCP sensor. The following plot shows the sound speed in the water column over the course of the trials, where the sound speed is measured in m/s:
Throughout the trial, the sound speed in the water column varied from around 1511.3 m/s to 1511.8 m/s, which is a very small variation (~0.03%). The sound speed in the water column is important as it is used in combination with the time delay of the acoustic signal to estimate the difference in propagation distances.
Recovery
On October 6th, 2021, the underwater platform was recovered from the berm. The platform was in good condition, with all systems functional.
More Information
For even more technical information on the platform and tests performed, please see my Thesis sections “4.2 Parrsboro Berm Trial” and “4.4 Long Term Deployment in the Bay of Fundy”.