Dead reckoning
In navigation, dead reckoning or dead-reckoning (from (correct) ded for deduced reckoning or DR) is the process of calculating one's current position by using a previously determined position, or fix,...
South Pointing Chariot
The south-pointing chariot (or carriage) was an ancient Chinese two-wheeled vehicle that carried a movable pointer to indicate the south, no matter how the chariot turned. Usually, the pointer took th...