Today, probably, there is no person who has not heard about GPS. However, not everyone has a complete understanding of what it is. In the article we will try to figure out what the global positioning system is, what it consists of and how it works.
History
The GPS navigation system is part of the Navstar complex, developed and operated by the US Department of Defense. The project of the complex began to be implemented in 1973. And already at the beginning of 1978, after successful testing, they put it into operation. By 1993, 24 satellites had been launched around the Earth, completely covering the surface of our planet. The civilian part of the Navstar military network became known as GPS, which stands for Global Positioning System ("global positioning system").
Its base consists of satellites that move in six circular orbits. They are only one and a half meters wide, and a little more than five meters long. The weight in this case is about eight hundred and forty kilograms. All of them provide full performance anywhere on our planet.
Tracking is carried out from the main control station, located in the state of Colorado. There is the Schriver Air Force Base - the fiftieth space force.
There are over ten tracking stations on Earth. They are found on Ascension Island, Hawaii, Kwajalein, Diego Garcia, Colorado Springs, Cape Canaveral and other places, the number of which is growing every year. All information received from them is processed at the main station. Updated data is uploaded every twenty-four hours.
This global positioning is a satellite system operated by the US Department of Defense. It works in any weather and constantly transmits information.
Operating principle
GPS global positioning systems work on the basis of the following components:
- satellite trilateration;
- satellite ranging;
- exact time reference;
- location;
- correction.
Let's take a closer look at them.
Trilateration is the calculation of the distance of the data of three satellites, thanks to which it is possible to calculate the location of a certain point.
Ranging means the distance to the satellites, calculated by the time it takes for the radio signal to travel from them to the receiver, taking into account the speed of light. To determine the time, a pseudo-random code is generated, thanks to which the receiver is able to fix the delay at any time.
The following figure indicates a directdepending on the accuracy of the clock. The satellites have atomic clocks that are accurate to one nanosecond. However, due to their high cost, they are not used everywhere.
The satellites are located at an altitude of more than twenty thousand kilometers from the Earth, exactly as much as is necessary for stable movement in orbit and narrowing of atmospheric resistance.
During the operation of the global positioning system in the world, mistakes are made that are difficult to eliminate. This is due to the passage of the signal through the troposphere and ionosphere, where the speed decreases, which leads to measurement failures.
Components of a mapping system
There are many global positioning system products and GIS mapping applications. Thanks to them, geographic data is quickly formed and updated. The components of these products are GPS receivers, software and data storage devices.
Receivers are able to make calculations with a frequency of less than a second and an accuracy of tens of centimeters to five meters, operating in differential mode. They differ from each other in size, memory capacity and the number of tracking channels.
While a person is standing in one place or moving, the receiver receives signals from satellites and makes a calculation about its location. Results in the form of coordinates are shown on the display.
Controllers are portable computers that run the software needed to collect data. The software controls the receiver settings. Drives havedifferent dimensions and types of data recording.
Each system is equipped with software. After you upload information from the drive to your computer, the program increases the accuracy of the data using a special processing method called "differential correction". The software visualizes the data. Some of them can be edited manually, others can be printed, and so on.
GPS global positioning - systems that help collect information for entry into databases, and the software exports them to GIS programs.
Differential correction
This method significantly improves the accuracy of the collected data. In this case, one of the receivers is located at a point of certain coordinates, and the other collects information where they are unknown.
Differential correction is implemented in two ways.
- The first is the real-time differential correction, where the errors of each satellite are calculated and reported by the main station. The updated data is received by the rover, which displays the corrected data.
- The second - differential correction in post-processing - takes place when the main station writes corrections directly to a file in the computer. The original file is processed together with the updated one, then a differentially corrected one is obtained.
Trimble mapping systems are capable of using both methods. Thus, if the real-time mode is interrupted, then it remains possible to use it in post-processing.
Application
GPSapplied in different areas. For example, global positioning systems are widely used in the natural resources industry, where geologists, biologists, foresters, and geographers use them to record positions and additional information. It is also an area of infrastructure and urban development where traffic flows and the utility system are controlled.
GPS-systems of global positioning are also widely used in agriculture, describing, for example, the features of fields. In the social sciences, historians and archaeologists use them to navigate and record historic sites.
The scope of GPS mapping systems is not limited to this. They can be used in any other application where precise coordinates, time and other information are needed.
GPS receiver
This is a radio receiver that determines the position of the antenna based on information about the time delays of radio signals from the Navstar satellites.
Measurements are formed with an accuracy of three to five meters, and if there is a signal from a ground station - up to one millimeter. Commercial-type GPS navigators on old samples have an accuracy of one hundred and fifty meters, and on new ones - up to three meters.
Based on receivers, GPS loggers, GPS trackers and GPS navigators are made.
Equipment can be custom or professional. Seconddiffers in quality, operating modes, frequencies, navigation systems and price.
Custom receivers are capable of reporting precise coordinates, time, altitude, user-specified heading, current speed, road information. Information is displayed on the phone or computer to which the device is connected.
GPS navigators: maps
Maps improve the quality of the navigator. They come in vector and raster types.
Vector variants store data about objects, coordinates and other information. They can feature natural terrain and many objects such as hotels, gas stations, restaurants, etc., as they do not contain images, take up less space and work faster.
Raster types are the simplest. They represent an image of the area in geographic coordinates. A satellite photo can be taken or a paper type map - scanned.
Currently, there are navigation systems that the user can supplement with their objects.
GPS trackers
Such a radio receiver receives and transmits data to control and track the movements of various objects to which it is attached. It includes a receiver that determines the coordinates, and a transmitter that sends them to a user located at a distance.
GPS trackers come in:
- personal, used individually;
- automobile, connected to the onboardauto networks.
They are used to locate various objects (people, vehicles, animals, goods, and so on).
These devices can be used to suppress signals that form interference at the frequencies where the tracker operates.
GPS-logger
These radios are capable of operating in two modes:
- regular GPS receiver;
- logger, recording information about the path that has been traveled.
They can be:
- portable, equipped with a small-sized rechargeable battery;
- automobile, powered by the on-board network.
Modern logger models can record up to two hundred thousand points. It is also suggested to mark any points on your way.
Devices are actively used in tourism, sports, tracking, cartography, geodesy and so on.
Global positioning today
Based on the information provided, it can be concluded that such systems are already used everywhere, and the scope tends to be even more widespread.
Global positioning covers the consumer sector. The use of the latest technical innovations makes the system one of the most sought after in this market segment.
Along with GPS, GLONASS is being developed in Russia, and Galileo in Europe.
At the same time, global positioning is not without its drawbacks. For example, in an apartment of a reinforced concrete building, in a tunnel or basement, determine the exact locationimpossible. Magnetic storms and radio sources on the ground can interfere with normal reception. Navigation maps quickly become outdated.
The biggest drawback is that the system is completely dependent on the US Department of Defense, which at any time can, for example, turn on interference or turn off the civilian part altogether. Therefore, it is so important that in addition to the global positioning system GPS and GLONASS, and Galileo are also developing.
