3 ms·

That is astounding! something I was unaware about before. At what depth could it be measured?

• grendelt 6y ago
  Almost any depth. A big steel tube is going to displace water. Once you have some baseline measurements (of known underwater landforms), then small imperceptible variations would stick out.
  • SirLuxuryYacht 6y ago
    Not possible. The uncertainty of bathymetry in areas only mapped using gravity is larger than the dimensions of a sub. Even in very well mapped areas, think of the effort in the Indian ocean to find MH370, this would require the assumption that the sub is moving, which is not always the case, e.g. if the sub halts propulsion and drifts with a current.
    • geomark 6y ago
      Well yes, it's the surface disturbance of the underwater wake that they are detecting. So the sub has to be moving under its own power. But there is no need for high resolution and the wake of the sub stands out starkly even with a large field of view. So I'm not sure it can evade detection by halting propulsion and drifting. The point at which it halted would be known and it would be detected as soon as it restarted, unless it was carried by an unknown current far enough to be out of view of the satellite.
• baybal2 6y ago
  The infamed laser on Tu 142 was said to get to only get to 50m, but that was a "direct imager" which relied on direct reflection, and seventies-eighties era technology. Newer ones are directly sensing density, and temperature changes in the seawater by sensing Raman shift, and are supposedly much better. No known data in public of course.