The object of this paper is to present various practical solutions to the problems of inertia navigation in a descriptive rather than a mathematical form. Inertia navigation is an automatic bump of locality, a dead-reckoning device which, starting from a known point, seeks to find position. Other dead-reckoning devices measure speed, which is only relative to the fluid sea or air. Inertia navigation measures accelerations, which are absolute, and hence builds up a measure of speed. The accelerometer is, therefore, a good starting point for our survey.