Global Positioning Systems (GPS) have been around for sailors since 1990. It is the sailor’s modern way of determining everything we need, including longitude, latitude, time, speed, course, heading and distance, all at the touch of a button. The funny thing about this modern technology is that it is based on the same process of triangulation that we used on the boat. Remember how we needed three bearings to determine where we were on the chart? Well the GPS needs three “satellite fixes” to determine where we are as well. The way the computer plots our position is to figure out how long it takes for a certain radio signal to reach us from the satellite. Once again time is very important in determining our location. The radio signal is very weak, so it takes accurate computers to get an accurate reading. The signal is 1 ten quadrillionth of a watt. That is about equal to the light from a 20-watt bulb reaching us from 11,000 miles away. So although it is a great tool to have, we don’t want it to be our only source of navigational data. We still want to keep our own accurate measurement by using our compasses, watches, sextants etc.

Questions: Click on the question to see the answer

What other technological gadgets rely on satellites?

Can you name any natural satellites?

Marine Biology
Marine Ecology
Marine Navigation

The distance north or south of the equator measured and expressed in degrees.

The distance in degrees east or west of the meridian at Greenwich, England.

A celestial body orbiting another of a larger size, or a manufactured object intended to orbit the earth, moon, or another celestial body.

A navigational tool used to determine position by measuring the angle of celestial bodies above the horizon.

The geometric process of determining a geographical position using two or more compass bearings.