Nomads made up stories to remember the positions of the stars. They then used the constellations in the stories to guide themselves. This was the earliest form of navigation by the stars. Navigation has always been a very important part of astronomical studies. It has had a profound effect on people over time.

Early measurements of latitude were made during the middle ages. They were based on the pole star and the sun. This worked pretty well, but not exactly, since the pole star was not exactly at the celestial pole. It was necessary to account for this error in finding latitude.

Many instruments were used to find the angle of the stars and to find latitude. In 1595 Captain John Davis invented the backstaff. It was used especially in sea navigation. The sestant was used for navigation a lot during earlier times. It had several mirrors used to measure the angle of the sun and mooon.

Stars could also be used to tell time. An instrument called a night dial or nocturnal was used to tell time at night. The nocturnal is a clock face and one sights the pole through the center. There is a hand to point at a specific star and read the time on the dial. Time which is measured this way is known as “sidereal time”. It is important in making measurements with respect to the spinning earth.

Longitude was more difficult to find than latitude. A rewarad of 20,000 pounds was offered by the British to anyone who could accurately measure longitude. In 1761 John Harrison invented the chronometer, a shipboard clock that stayed very accurate. Now people could find latitude and longitude.

Radio navigation was used during the 1900's. It was used widely during World War II. The problem with radio navigation was that you either had a wide range and low accuracy or a small range, but high accuracy. People thought a satellite navigation system would work better.

Today we have Global Positioning Systems which can find your exact location. GPS has many uses, such as guidance for cars. It is also used on golf courses to find the exact location of the ball and distance from the pin. GPS can be used in agriculture too. Farmers can put in maps of the soil and yields, and using GPS to pinpoint their location, adjust their seed and fertilizer rates. This can help them save money, but the GPS units are still quite expensive.