Inertial Navigation on Earth... and Beyond


Just as motion along the surface of the Earth, and motion towards or away from the center of the Earth causes predictable changes in the direction of down, the rotation of the Earth causes predictable changes in the relationship between the local level frame and inertial space. As before, errors in making these predictions result in further errors, in this case, what are called Earth loop errors. These errors can be initiated by the same kinds of events that initiate Schulers (in most cases events that will cause an earth loop error, also cause a Schuler), but because they involve errors in anticipating alignment changes caused by the rotation of the earth, the period of these errors is about 24 hours (or harmonics thereof).

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