What is GPS?
GPS, or the Global Positioning System, is a global navigation satellite system that provides location, velocity and time synchronization.
GPS is everywhere. You can find GPS systems in your car, your smartphone and your watch. GPS helps you get where you are going, from point A to point B. What is GPS? Read this article to learn more about how it works, its history and future advancements.
What are the three elements of GPS?
GPS is made up of three different components, called segments, that work together to provide location information.
GPS consists of the following three segments.
Space segment (GPS satellites)
A number of GPS satellites are deployed on six orbits around the earth at the altitude of approximately 20,000 km (four GPS satellites per one orbit), and move around the earth at 12-hour-intervals.
Control segment (Ground control stations)
Ground control stations play roles of monitoring, controlling and maintaining satellite orbit to make sure that the deviation of the satellites from the orbit as well as GPS timing are within the tolerance level.
User segment (GPS receivers)
The user segment consists of the GPS receiver equipment, which receives the signals from the GPS satellites and uses the transmitted information to calculate the user's three-dimensional position and time.
How Does GPS Work?
The Short Answer:
GPS is a system of 30+ navigation satellites circling Earth. We know where they are because they constantly send out signals. A GPS receiver in your phone listens for these signals. Once the receiver calculates its distance from four or more GPS satellites, it can figure out where you are.
The GPS (Global Positioning System) consists of 24 medium earth orbit satellites developed by the US Department of Defense and currently managed by the US Air Force 50th Space Wing. Each satellite transmits microwave signals to the earth. GPS receivers on the earth use these signals to determine their locations, speed, direction, and time. A typical GPS receiver must have line-of-sight with satellites to calculate its position using signals from four or more GPS satellites. Four satellites are needed since the process needs a very accurate local time for the device to determine its time as well as position. These signals are then processed by the receiver to determine latitude/longitude, speed, altitude, and time. For fleet management systems, this set of data is transmitted over a wireless network to a server. The server then takes the data and uses it to provide the end user with locations of their devices.
1. Tracking stations use radio signals to determine orbits of GPS satellites.
2. Command center transmits orbital data, time corrections, and location of other satellites in the GPS constellation.
3. GPS satellites simultaneously transmit synchronized time and orbital data to Earth.
4. GPS receivers compute location using orbital data and the difference in arrival times of the signals of at least 4 satellites.
What are the uses of GPS?
Your imagination is the only limitation to the possibilities of Global Positioning System (GPS) technologies. GPS systems are extremely versatile and can be found in almost any industry sector. They map forests, help farmers harvest their fields, and navigate airplanes on the ground or in the air. Positioning systems are integral to military applications, and for emergency crews to locate people in need of assistance. GPS technologies are often working in many areas that we do not normally consider.
Global Positioning System applications generally fall into 5 major categories:
1. Location – determining a position
2. Navigation – getting from one location to another
3. Tracking – monitoring object or personal movement
4. Mapping – creating maps of the world
5. Timing – bringing precise timing to the world
Advantages and Disadvantages of GPS
Advantages of GPS
Following are the advantages of GPS:
➨The GPS signal is available anywhere on the globe. Hence user will not deprive of GPS facility anywhere.
➨There is no charge to utilize the GPS service as US Defence bears cost of GPS system. It is maintained and upgraded by US Department of Defence. It is cheaper compare to other navigational systems.
➨The GPS system gets calibrated by its own and hence it is easy to be used by anyone.
➨It provides user with location based information. This will be helpful in various applications such as mapping (used in cars), location (geocaching), performance analysis (used in sports), GIS etc. Example: Google Earth Application.
➨GPS helps find retail outlets in new visitor location.
Disadvantages of GPS
➨GPS chip is power hungry which drains battery in 8 to 12 hours. This requires either battery replacement or recharge.
➨GPS signal does not pierce through the solid walls or structures. Moreover it is affected by large buildings or structures. Due to this, user will not be able to utilize GPS service in indoors or under water or in dense tree regions or in underground stores or places etc.
➨GPS accuracy depends on sufficient received signal quality. GPS signal gets affected due to multipath, atmosphere (i.e. ionosphere), electromagnetic interference etc. This leads to error of about 5 to 10 meters in GPS signal.
➨Though currently system is managed by US DoD and users are utilizing the system free of cost, it is in the hand of US to allow or deny the GPS service at anytime.
➨It is better not to rely completely on GPS system. Backup travel maps with directions will help in the event of GPS system failure.
A Brief History of Global Positioning System(GPS)
GPS has its origins in the Sputnik era when scientists were able to track the satellite with shifts in its radio signal known as the "Doppler Effect." The United States Navy conducted satellite navigation experiments in the mid 1960's to track US submarines carrying nuclear missiles. With six satellites orbiting the poles, submarines were able to observe the satellite changes in Doppler and pinpoint the submarine's location within a matter of minutes.
In the early 1970's, the Department of Defense (DoD) wanted to ensure a robust, stable satellite navigation system would be available. Embracing previous ideas from Navy scientists, the DoD decided to use satellites to support their proposed navigation system. DoD then followed through and launched its first Navigation System with Timing and Ranging (NAVSTAR) satellite in 1978. The 24 satellite system became fully operational in 1993.
Today, GPS is a multi-use, space-based radionavigation system owned by the US Government and operated by the United States Air Force to meet national defense, homeland security, civil, commercial, and scientific needs. GPS currently provides two levels of service: Standard Positioning Service (SPS) which uses the coarse acquisition (C/A) code on the L1 frequency, and Precise Positioning Service (PPS) which uses the P(Y) code on both the L1 and L2 frequencies. Access to the PPS is restricted to US Armed Forces, US Federal agencies, and selected allied armed forces and governments. The SPS is available to all users on a continuous, worldwide basis, free of any direct user charges. The specific capabilities provided by SPS are published in the Global Positioning System Performance Standards and Specifications.
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