^^ That's OK... I'm glad to change the subject to be honest!
Good question OhOh... nice to get away from my past indiscretions.
First... it's an ROV. An SUV is something you use to drive your kids to school in Chelsea.
For a route survey, or any kind of work away from platforms, the ROV will fly along a specified route and the ship will follow... called 'follow sub' mode. The ship is positioned by satellite, from which the ROV is positioned by acoustic navigation. The ROV position is then broadcast by a transponder or responder and the ship's navigation system is locked into the ROV position. The ship's thrusters are computer controlled and can hold the ship's position to metric accuracy.
On a typical route survey there is very little to spot online (in real time). The ROV may fly 10 to 15 metres above the seabed acquiring multibeam echosounder, side scan sonar and sub-bottom profiler data. We'll survey a swath of seabed, from which a route can be decided on. We check that all data has been acquired before leaving a location but processing/interpretation can take many weeks. For example the data I am currently working with was for a route/site survey in the Barent's Sea acquired in July (coincidentally for the same project I worked on last year with a different contractor).
We like to have at least one survey line directly along the centreline of a proposed route since the shallow seismic is acquired directly below the vehicle. Other data may be collected at ranges of maybe 50m to 200m either side of the vehicle. We usually collect data along several winglines, making sure of good data overlap and sufficient density, to survey a corridor maybe 200m to 500m wide. Much of that depends on how much the client is willing to pay... each wingline takes time and costs money.
The ROV doesn't go off course from planned routes unless there has been a problem... a navigation run-off or maybe particularly strong water current. The client doesn't pay if we're off course and surveying a random piece of seabed. Survey lines are fed into the navigation system and much of the ROV piloting is automated. AUVs (Autonomous Underwater Vehicles) have no umbilical and are becoming more common for survey work... using these, the survey line coordinates, survey altitude, etc are fed in, the AUV is launched and completes the survey lines before being recovered. Their main limitation is battery life.
Of course there's many variations on the theme. For visual pipeline inspections, the ROV will fly along a pipeline at an altitude of maybe just a couple of metres, and hopefully anything significant, maybe a mine, will be noticed in real time, in which case we'll stop the survey to take appropriate steps. Final phases of route surveys may also require visual surveys along a decided route, but by that stage anything significant should have been identified during previous surveys.
Edit: She wasn't a Grandma... she was just older than me and I was very young at the time. Also, I distinctly remember stating that I wasn't going to say how the evening turned out.
Let's keep this to work questions!