Who needs a GPS. Just use these formulas and calculators to find out where you are. 
Calculate distance, bearing and more between two latitude/longitude points 
Standard Distance Conversions:


For every 15° that one travels eastward, the local time moves one hour ahead. Similarly, travelling West, the local time moves back one hour for every 15° of longitude. Therefore, if we know the local times at two points on Earth, we can use the difference between them to calculate how far apart those places are in longitude, east or west. This idea was very important to sailors and navigators in the 17th century. They could measure the local time, wherever they were by observing the Sun, but navigation required that they also know the time at some reference point, e.g. Greenwich, in order to calculate their longitude. Although accurate pendulum clocks existed in the 17th century, the motions of a ship and changes in humidity and temperature would prevent such a clock from keeping accurate time at sea.
