Every now and then, something for sale on Amazon.com seems so monumentally stupid that it inspires a spontaneous community comedy festival. One person after another leaves phony reviews, each more heartfelt and over-the-top than last, sardonically praising the Amazon item for its astonishing, life-changing abilities. Perfect strangers, entertaining each other in the comments, laughing their heads off—until Amazon gets wind of the stunt and shuts it down.
Inertial Navigation (IN) Theory Made Easy
The following explanation, in simplified terms, is typical of all IN systems:
1. An aircraft knows where it is at all times; it knows this because it knows where it isn't.
By subtracting where it is from where it isn't, it obtains a difference, termed deviation.