3 ms·
> When there aren't clear skies to see stars, what other sort of non-GPS calibration could be done at sea? It is speculated that you could keep navigational er
by krisoft 4y ago
> When there aren't clear skies to see stars, what other sort of non-GPS calibration could be done at sea?
It is speculated that you could keep navigational errors bounded with gravimetric measurements. Essentially if you have a detailed pre-surveyed map of the underwater landscape, and high precision gravity measurements you can match your measurements to the undulations of the expected gravity field. Somewhat similar, at least on the math level, to how TERCOM works with cruise missiles.
- HPsquared 4y agoWouldn't the movement of the boat cause too much "noise" for these kinds of measurements? How would they cancel out small movements due to e.g water currents?
- krisoft 4y agoThe short and true answer is that if I would know for sure I could not write about here. Hence all of this is speculation. Very likely they would use the best motion isolation money can buy. Also the submarine is quite slow (especially at navigation speeds) so the terrain changes under it slowly. Water currents and the motion of people and machinary happens at much higher rate, so you can probably try to eliminate the quick changes and keep the slower changes with filtering and statistics.
- ISL 4y agoIt isn't as hard as you might think. Most gravity-gradient measurements are differential. Common-mode accelerations can be substantially-rejected. Also, if you're in the precision-measurement game, navigationally-relevant signals can be much larger than the precision of modern instruments. People in the prospecting business sometimes fly gravity-gradiometers in airplanes.