As navigator, Lovell took with him a sextant to take star readings - in case the computers failed and they had to find their own way home.
Automatic transcription
，这一点在同城约会中也有详细论述
A new transaction is added to the system. It is then relayed to a network of computers located around the world. The computers then solve equations to ensure the authenticity of the transaction.
Shortcut Pre-calculation: For the most commonly used speed profiles, the travel costs (time/distance) for shortcuts between border points within each cluster are pre-calculated and stored. (Each border point effectively has an "entry" and "exit" aspect for directed travel).