We had our first dive in a ex-mining lake a few days back. Not an entirely positive experience - lifeline entangled with the propeller and then there was a waterleak - but it was a learning step.
I am wondering about the following; deep down in the water, when the BlueROV is no longer visible from above, and not having an underwater GPS device and the camera showing nothing but turbid nothingness, how do u have a sense of where the ROV is and in which direction it should be going. On the one hand, we wanted to explore at will. On the other hand, we have to take care of the tether, not wanting ROV to go out of range and tug it badly. I worked out that I have to observe the movement of the tether, it does give a fair idea, but then we were no more than 10m deep that day.
How do you yourself do it - confidently navigating the ROV deep out of sight (without GPS)?
Hi @NordinZ -
Hope you found the source of your leak!
Without visual reference, a sensor, usually acoustic is necessary if you want to keep the ROV from drifting, or know its position. For some missions, diving straight down as fast as possible to find the bottom, and a visual reference, is the best approach. For finding objects at a specific target, dropping a weight with attached line and surface float can give you a “road” to follow down, with the line leading to the approximate location of interest.
A DVL sensor locks onto the bottom, from 50 or 125m away (for WaterLinked units), and measures the relative velocity of the vehicle to it. This gives the ROV functional position hold mode - so you could descend vertically without following a rope!
To know GPS position, WaterLinked makes an acoustic GPS solution, and Cerulean has a similar product.