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GPS and Navigation

Many consumers have come to rely on GPS and navigation systems in their daily travels.

GPS or a navigation system is great when traveling. [©Jupiter Images, 2009]
©Jupiter Images, 2009
GPS or a navigation system is great when traveling.

GPS and Navigation

GPS and navigation have a storied history together, with navigation paving the way for the implementation of the Global Positioning System (GPS). Until the 20th century, navigation referred solely to the guidance of ships across water. With the advancement of GPS, navigation now refers to directing transformational devices on land or through the air or sea. The success of the GPS navigational tool is expected to increase, according to CNET, which states that by 2012 there may be 560 million handsets worldwide, compared to the 175 million that were on the market in 2007.

Navigation History

Navigation essentially refers to the way of getting from one place to another safely and efficiently. The first record of navigation occurred around 3500 B.C. when boats sailed the seas to deliver goods. The ship's navigators kept the vessel close to shore and watched for landmarks or specific land characteristics to determine where they were. If the ship traveled too far from land, the navigators were able to use the sun's position during the day and the North Star's position at night to determine their location's latitude, which is the north/south direction.

Navigational tools expanded after the 12th century. One addition to marine navigation was the magnetic compass, which was first used during the 12th century. The needle of the compass always points north, so even when the navigators did not know where they were, they knew the direction they were heading. Nautical charts were another popular option that sprung up during the mid-14th century. The charts provided mariners with written documentation as to their travels and were oftentimes kept secret from other mariners. The sextant was a tool designed in the mid-18th century, and it measured the exact angles of the stars, moon and the sun above the horizon through adjustable mirrors. This device was able to provide travelers with the first accurate calculation of latitude.

Radio-based navigational systems were used in the early 20th century, mainly during World War II. Ships and airplanes could use ground-based systems, but users had to choose between a lower-frequency system, which covered a wide area but transmitted less-accurate data, or a higher-frequency system, which covered a shorter area but provided accurate readings.

Development of GPS

Two significant advances in navigation spurred the birth of the Global Positioning System. The United States developed Long Range Navigation (Loran) between 1940 and 1943, which used radio transmissions sent between master and slave stations to determine a vessel's position. The accuracy of Loran was measured in hundreds of meters, but like the radio-based systems used just a few years prior the Loran had limited coverage.

When Russia launched Sputnik into orbit on October 4, 1957, researchers at the Massachusetts Institute of Technology noticed that the satellite could be used as an artificial star for navigational purposes. Sputnik's radio signals increased as it approached orbit and decreased as it left orbit. This was the first step in determining that a satellite's location could be documented from land and that the satellite could determine a subject's location on the ground with the help of radio signals.

Updating the Loran, GPS received the green light near the end of the 20th century. According to the National Park Service, on June 26, 1993, the U.S. Air Force launched the 24th Navistar satellite into orbit, which was the final satellite in the network of the Global Positioning System. Each one of the satellites transmits an accurate position and time signal. The user's receiver determines the time delay in receiving the transmission, which is the direct measure of the satellite's range. The measurements are collected from four satellites at the same time, with the results determining the user's position, velocity and time. Some GPS devices may convey other information, such as distance and bearing to specific destinations.

GPS Navigation Systems

Today's GPS devices can cost less than a few hundred dollars and allow travelers to know their exact location, including the location's latitude, longitude and even altitude. GPS works every hour of every day, regardless of the type of weather or location. This United States-owned entity is operated, developed and maintained by the U.S. Air Force and the U.S. Department of Defense. Although GPS is maintained by U.S. governmental agencies, the system's services are available to both military personnel and to civilians. The military service is available to U.S. and allied armed forces as well as approved government agencies. The government decided to offer the GPS service to civilians in the 1980s, and today civilians can access GPS without any subscription fees or set-up charges. The only cost to the consumer is the cost of a GPS receiver.

According to the U.S. Department of Homeland Security, GPS consists of three segments, which include:

  • Space segment -- There are 24 operational satellites that orbit in six circular orbits. The six orbits allow at least six of the satellites to be in view at any time all over the world since the satellites broadcast position and time information to interested parties at all times.
  • Control segment -- The master control station is located in Colorado Springs, Colo., with five monitor stations and three ground antennas located across the world. These stations track the satellites and collect ranging information from the satellite broadcasts. The monitor stations send the collected information to the master station, and the master station formats the information into navigational messages for the satellites.
  • User segment -- This group is comprised of receivers, processors and antennas that allow operators to receive the GPS satellite broadcasts, which in turn allows users to determine their location in terms of position, velocity or time.

The GPS satellites broadcast signals, which are picked up by receivers. Consumers can purchase GPS handsets through commercial retailers, allowing them to accurately know where they are as well as easily navigate the direction they need to travel. A two-dimensional GPS position determines the longitude and latitude, while a three-dimensional position includes longitude, latitude and altitude.

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