Global Positioning System (GPS) is a technology that uses satellite signals to pinpoint your location on Earth, and it has become an essential tool for everyday life and a wide range of industries. Currently, GPS is used in many areas, including car navigation, agriculture, and autonomous vehicles, with more applications expected as the technology evolves.
The Global Positioning System (GPS) is a satellite-based positioning system developed by the United States. Anyone who works in surveying today is familiar with the term GPS. This technology has been around since the late 20th century and is now deeply embedded in our daily lives. Beyond the field of surveying, GPS is also widely used by the general public, from car navigation to GPS cell phones to wayfinding in outdoor activities. As such, GPS has become an essential tool in many aspects of life.
GPS is composed of three main parts. First, the space part of the system consists of GPS satellites. There are 24 GPS satellites (21 navigational satellites and three spare satellites) in orbit around the Earth every 12 hours. The altitude of the orbits is about 20,000 kilometers. There are six orbits (four satellites in each orbit), equally spaced (60 degrees apart) and at an inclination of about 55 degrees to the equatorial plane. This arrangement is intended to provide users anywhere on Earth with between five and eight satellites at any given time. The precise placement and operation of the satellites is an important factor in ensuring the high reliability of GPS.
The second, the control segment, consists of control stations (tracking) located around the world, which measure the signals from each satellite. These stations play a key role in maintaining the accuracy of the GPS system and are responsible for fine-tuning satellite orbits and clock errors.
The third segment of GPS users consists of GPS receivers and user groups. GPS receivers convert signals from satellites into estimated position, velocity, and time. Four satellites are required to calculate the four dimensions of X, Y, Z (three-dimensional position) and time. GPS receivers are used for navigation, positioning, time propagation, and other research. In recent years, GPS technology has been utilized in a variety of industries to significantly increase productivity and efficiency. For example, in agriculture, the concept of precision farming has been introduced, and automated systems utilizing GPS are helping farmers manage their crops more efficiently and increase productivity.
GPS positioning determines location by measuring the distance between a satellite and a user. For each of the three satellites whose position in space is known, the position can be calculated by knowing the distance between them. The distance is determined by an atomic clock on the satellite, which measures the time it takes for the signal it is sending out to reach the receiver at that precise moment. If the GPS receiver’s clock and the satellite’s clock are in perfect synchronization, the signal’s arrival time will tell you how long it took to be transmitted. However, it is nearly impossible to get the GPS receiver and satellite clocks to perfectly match. This means that there are four unknowns: the GPS receiver’s three-dimensional position coordinates (X, Y, and Z) and the time difference between the two clocks. Then, by receiving signals from four or more satellites simultaneously, an equation is calculated to determine the unknowns.
GPS has a number of unique features. First, GPS has a wide range of accuracy, from a few millimeters to tens of meters, depending on the positioning technique, so it uses the appropriate positioning technique for the surveying purpose. For example, if you need high accuracy, you would choose a static positioning technique, which can have an accuracy of a few millimeters, although it requires a lot of survey time and effort. On the other hand, if you have a large number of datum points to determine your position and the accuracy required is not very high, you will use dynamic positioning, for example, which can efficiently determine your position in a short time.
Second, GPS can be positioned anywhere on Earth and even in outer space, regardless of weather and weather conditions, as long as a satellite signal is available. This means that it has fewer limitations than traditional surveying methods, which require visibility. However, it does require a clear view of the sky and the ability to receive four or more satellites simultaneously.
The third is that it has a high accuracy relative to the length of the line. For traditional surveying methods, the error increases proportionally with the length of the plume, but GPS is relatively unaffected by plume length. Of course, if the tracks are close together, various error factors can be reduced, which increases accuracy. However, even for long-distance surveys, where the line length is more than 10 kilometers, the decrease in accuracy due to the increase in line length is small.
In addition to these advantages, GPS is widely used in everyday life due to its ease of use, efficiency, and speed. GPS is being modernized to increase its positioning capabilities. In addition, the EU is developing Galileo and Russia is developing GLONASS to complement Galileo, making the three satellite systems work together. This is expected to enable faster and more accurate positioning, making satellite positioning more effective in a wider range of applications. This will be especially true for high-tech applications such as autonomous vehicles and smart logistics systems, so having a basic understanding of GPS will help you to use it effectively.
