GPS is a global navigation satellite system that allows us to accurately determine the position of an object, person, vehicle, or ship worldwide, up to centimeters. The GPS system was developed, installed and operated by the US Department of Defense.
GPS (Global Positioning System)
In 1952, the Soviet Union launched the Sputnik I satellite, which was monitored by observing the Doppler effect of the signal it transmitted.
Therefore, similarly, studies were initiated where an observer’s position could be established by examining the Doppler frequency of a signal transmitted by a satellite whose orbit was precisely determined.
The U.S. Navy used this technology to provide current and accurate location observations to their fleet’s navigation systems.
The TRANSIT system, which became operational in 1964, emerged and commercial use began in 1967.
At that time, position updates were taking place every 40 minutes, and the observer had to be almost completely stationary to get enough information.
Later, in the same decade and thanks to the development of atomic clocks, a constellation was designed, each carrying one of these clocks and all synchronized according to a specific time reference.
In 1973, the Navy and the United States Air Force programs developed an encrypted transmission technique that provided accurate data using a signal modulated with a PRN code, which was later renamed NAVSTAR GPS.
Between 1978 and 1985, 11 experimental NAVSTAR prototype satellites were developed and launched, followed by other generation satellites, completing the existing constellation, declared as “First Operational Ability” in December 1993 and “Full Operational Ability” in April 1995.
On May 2, 2000, Bill Clinton signed an agreement to turn on A-GPS (Accurate GPS) for all civil uses, and in 2009 signed an agreement with ICAO (International Civil Aviation Organization) on the use of GPS in air navigation.
Cuba, along with Chinese Technologies, GPS, or Vehicle Computers, decided to integrate these systems into land and marine resources.
The main objectives of this monitoring were to give you more control over everything to gain the benefits used by mobile phones, such as saving fuel.
Development of GPS System
GPS is moving towards a more robust system that provides more usability and reduces its complexity.
The GPS III program aims to ensure that it meets military and civilian requirements. This program was developed using a very flexible approach that can be configured for future changes and reduce risks.
The system developed and new positioning systems were obtained after that. IPS-2 (Inertial Positioning System) is a data capture system that allows the user to measure in real-time and on the go, called Mobile Mapping.
This system achieves 3D mobile mapping based on a laser scanner, an inertial sensor, a GNSS system, and a device that collects an odometer in a vehicle.
Thanks to three positioning technologies IMU + GNSS + odometer, which offer measurement options even in areas where the satellite signal is not good during operation, great precision is achieved.
Earth in Space
Our closest star, the Sun, is just one of the billions of stars in the Milky Way.
The planet Earth is one of 9 planets that surround the Sun in an elliptical orbit. These planets closest to the Sun are the closest: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto.
The rules governing the movement of these solar planets have been studied in the discipline of Celestial Mechanics and were discovered hundreds of years ago by exceptional scientists such as Johannes Kepler and Isaac Newton.
The force that holds the 9 planets together and determines their relative movements is gravity.
The closer a planet is to the Sun, the more gravity is and it moves very fast in its orbit.
For example, the Earth, which is located approximately 150,000,000 km from the Sun, travels in orbit at an average of 30 kilometers per second and completes its rotation around the Sun in a year.
Satellites Orbiting the Earth
Scientists designed artificial satellites around Earth and Mars for detailed knowledge of the Celestial Mechanics rules and the study of the moons’ motion.
Powerful rockets are used to launch satellites into space. If the launch speed is too low, the satellite returns to Earth, which is pulled by the force of gravity.
If the launch speed is too high, Earth’s gravitational force will not be enough to keep the satellite in orbit.
Today, there are many satellites for the use of Telecommunications, Weather, Military applications, Scientific research, and Geophysical fields that orbit the Earth for different purposes.
The orbits of some satellites are synchronized with the Earth’s rotational period.
Satellites are called geostationary if their velocity coincides exactly with the Earth’s rotational speed, and always stays in the sky at the same point relative to Earth.
Some kind of communication is required to send satellites and to respond to the Earth from satellites.
Although there are many ways to do this, the main means of communication are radio waves used to broadcast television and radio programs.
Determining the position on Earth means providing the latitude and longitude of a particular point on the Earth’s surface.
Therefore, most receivers provide the values of these coordinates in degrees (°) and minutes (‘) and are both latitude and longitude angles. It should, therefore, be measured according to the well-defined 0° reference.
Latitude: Northern and Southern Hemispheres
Latitude is measured according to Ecuador (0 ° latitude). If a certain point is in the northern or southern hemisphere, the latitude coordinate will always be accompanied by the letter N or S. Another type of nomenclature refers to northern latitudes with positive numbers and southern latitudes with negative numbers.
Length: East, West
Longitude is measured relative to the Greenwich Meridian. If you measure an angle to the east or west of the Greenwich meridian, you write the letter E or W, accompanying the number that gives the longitude.
Global Positioning System
GPS (Global Positioning System) is 24 artificial satellites equally distributed in 6 orbits, with 4 satellites per orbit.
This ensures that at least 8 satellites are visible from almost anywhere on the Earth’s surface at all times.
GPS satellites orbit the Earth at an altitude of about 20,000 km and travel in two full orbits each day.
Each satellite transmits information about the location of radio signals and when the signal is emitted.
GPS receivers can be used to simultaneously decode signals sent by several satellites and combine their own locations on Earth, i.e. latitude and longitude coordinates, with an accuracy of approximately 10 meters. There are also better quality receivers that can determine the position with a few millimeters precision.
GPS receivers receive accurate information about the time and location of the satellite.
It takes exactly two types of data, Almanac data, which consists of a series of general parameters about the location and operation of each satellite relative to the rest of the satellites in the network, this information can be received from any satellite.
The GPS receiver knows where to search for satellites in space after having the latest Almanac and precise time information.
When the receiver captures the signals of at least three satellites, it calculates the location of the captured satellites on Earth and presents us the calculated Longitude, Latitude and Altitude data.
GPS receivers usually receive signals from more than three satellites to calculate their positions, and the more signals they receive, the more accurate the location calculation.
Considering that the first understanding of this system is to use it as military, it should be noted that the buyers in the market are for civil use and they are subject to deterioration insensitivity.
This is, of course, a strategic advantage during military operations that require this.
From all this, it is understood that GPS receivers generally have a nominal error of about 15 m in the position calculation.
If the use given to the GPS receiver requires more precision such as research, cartographic surveys, orientation races, cue location, almost all companies have optional antennas that correct this error for some of their receivers.
Usage Areas of GPS Receiver
You can use a GPS receiver for any purpose or project that you believe may be useful, and it should be noted that these are only data receivers that calculate the exact location and do not work with any analog data.
They are extremely useful devices for any navigation task, route tracking, point storage for further work, but in no case can you expect to extract atmospheric data from them.
However, even the models that GPS manufacturers offer for personal navigation have been used daily in aviation and marine navigation systems for years.
This includes a number of important benefits for GPS users for personal terrestrial navigation.
First, even if used in motor vehicles, the dimensions of aviation and naval navigation are much larger compared to the dimensions of land navigation.
This means that the receivers also have navigation sources and the accuracy of the larger ones.
The GPS receiver offers many more features than necessary for routing for terrestrial navigation.
Working Logic of GPS Receiver
The location of the satellites can be determined by the receivers, called Almanac, transmitted by the satellites themselves.
The collection of almanacs for the entire constellation is completed every 5-20 minutes and stored in the receiver.
Information useful for determining the location of the GPS receiver is called an ephemeris.
In this case, each satellite emits its own ephemeris information, which includes satellite health, its position in space, atomic time, and doppler information.
The GPS receiver uses the information sent by satellites and tries to synchronize its internal clock with the atomic clock on the satellites.
Synchronization is a trial and error process that takes place once a second on a portable receiver.
After the clock is synchronized, you can determine your distance from the satellites and use this information to calculate your location on earth.
Each satellite indicates that the receiver is at a point on the surface of the sphere, is centered on the satellite itself, and transmits the total distance to the receiver.
By acquiring information from two satellites, the receiver is said to be on the perimeter that arises when two spheres intersect.
If we get the same information from a third satellite, we will notice that the new sphere only cuts the previous perimeter at two points. One of them can be excluded because it offers a ridiculous position.
However, since the clock included in the GPS receivers is not synchronized with their atomic clocks, the two specified points are not certain.
With information from a fourth satellite, it eliminates the lack of synchronization between the hours of GPS receivers and the hours of the satellites.
Since the clocks are not synchronized between the receiver and satellites, the intersection of the four-center sphere in these satellites is a small volume.
DGPS (Differential GPS)
DGPS (Differential GPS) is a system that provides GPS receivers corrections in data from GPS satellites to provide greater accuracy in the calculated location.
Faults produced by the GPS system can equally affect recipients that are close together.
It transmits error correction to the receivers close to it so that it can also correct system-generated errors within the signal transmission coverage area of the reference GPS equipment.
It will be necessary to model the spatial and temporal changes of errors, increasing the coverage of DGPS corrections, and also minimizing the number of fixed reference receivers.
Advantages over Routing Systems
From the data sent by a constellation of orbiting satellites, it is as simple as satellites but has provided the reliability to use the sensitive technology available to humanity today.
They are used to predict atmospheric changes and environmental conditions for the development of the activity you want to perform.
In addition, all GPSs have navigation functions that will change the concept of direction.
For example, routes can be created on the map, you can save the desired points on the device, and if you enable this route, you can see if you are on the right track.
With all this data, it is also possible to detect the exact speed at which it moves while maintaining a direction in a straight line.
Using Received Data on Computer
If you need to transfer the data obtained with a GPS receiver to a computer to perform the necessary calculations, there are usually auxiliary tools for transferring data between PCs and GPSs.
In addition, certain software is required to import this data in a more or less standard way.
Because NMEA 0180,0181 and 0183 are the most common interfaces, software containing these interfaces can transfer over the serial port.
There are also RS232 interfaces that allow transfer from parallel ports. In addition, many GPS manufacturers that create their own socket structures have firm-specific interfaces.