We finished deploying all 42 OBEM receivers along the central profile and had SUESI in the water before lunch today, a comfortable 24 hours ahead of schedule.
While the team was hard at work launching SUESI, I was reformatting a real-time navigation code (originally written by Kerry Key) for this survey. It is now finally working! In the screenshot below, the leading black square shows SUESI’s current position, the red circle is the ship’s position, and the triangles are the surface GPS transponders (named Barracudas) that reply to pings from SUESI’s onboard acoustic unit. The bathymetry is shown in the background color map, the black lines are 100 meter depth contour intervals. The two-way travel time between SUESI and the Barracudas as well as the GPS positions of the Barracudas are communicated via the tow cable to a control terminal on a computer onboard the ship. The navigation code reads this information in along with the GPS position of the ship to calculate SUESI’s current position in the water. These data streams are updated every 15 seconds. Besides being a valuable tool for anticipating rough topography in SUESI’s tow path, this information is also critical for modeling the data to high accuracy during post-processing.