Today, probably, there is no person who would not hear about GPS. However, not everyone has a full understanding of what it is. In the article we’ll 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 back in 1973. And already at the beginning of 1978, after successful testing, it was put into operation. By 1993, 24 satellites were launched around the Earth, completely covering the surface of our planet. The civilian part of the Navstar military network began to be called GPS, which means the Global Positoning System ("global positioning system").
Its base consists of satellites that move along six circular paths of the orbit. They are only one and a half meters wide, and a little over five in length. The weight is about eight hundred and forty kilograms. All of them provide full performance anywhere in the world.
Tracking is carried out from the main control station located in the state of Colorado. There is Shriver Air Force Base - the fiftieth space formation.
On Earth, there are more than ten stations for tracking. They are located 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. Amendment data is downloaded every twenty-four hours.
Such global positioning is a satellite system operated by the United States Department of Defense. It works in any weather and constantly transmits information.
Principle of operation
GPS global positioning systems work on the basis of the following components:
- satellite trilateration;
- satellite range;
- exact time reference;
- location;
- correction.
Let's consider them in more detail.
Trilateration refers to 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.
Dalnometry means the distance to the satellites, calculated by the travel time of the radio signal 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 next indicator indicates a direct dependence on the accuracy of the watch. The satellites operate an atomic clock, the accuracy of which is up to one nanosecond. However, due to their high cost, they are not used everywhere.
Satellites are located at an altitude of more than twenty thousand kilometers from the Earth, exactly as much as is necessary for stable orbital motion and narrowing of atmospheric resistance.
When the global positioning system in the world, errors are made that are difficult to eliminate. This is due to the passage of the signal through the troposphere and ionosphere, where the velocity decreases, which leads to measurement errors.
Cartographic System Components
There are many products of the global positioning system and GIS mapping applications. Thanks to them, geographic data is quickly generated and updated. The components of these products are GPS receivers, software and data storage devices.
The receivers are capable of doing calculations with a frequency of less than a second and accuracy from tens of centimeters to five meters, operating in differential mode. They differ from each other in size, memory size 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. The results in the form of coordinates are displayed.
The controllers are laptop computers that operate under the control of software necessary for data collection. The software monitors the receiver settings. Drives have different dimensions and types of data recording.
Each system is equipped with software. After you download the information from the drive to the computer, the program increases the accuracy of the data using a special processing method called “differential correction”. The software visualizes data. Some of them can be edited manually, others can be printed, and so on.
GPS of global positioning is a system that facilitates the collection of information for entering into databases, and the software exports them to GIS programs.
Differential correction
This method significantly improves the accuracy of the data collected. 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 real-time differential correction, where the errors of each satellite are calculated and output by the main station. The updated data is perceived by the mobile receiver, which shows 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 the differential corrected one is obtained.
Trimble mapping systems can use both methods. Thus, if the mode in real time is interrupted, then there remains the possibility of its use in post-processing.
Application
GPS are used in various fields. For example, global positioning systems on the ground are widely used in the field of natural resources, where geologists, biologists, foresters and geographers use them to record positions and additional information. It is also an area of infrastructure and urban development, when traffic flows and the municipal system are controlled.
Widespread use of GPS-systems of global positioning was also obtained in agriculture, describing, for example, the features of fields. In the social sciences, historians and archaeologists use them to navigate and register historic sites.
The scope of GPS mapping systems is not limited to this. They can be used in any other applications where exact coordinates, time and other information are needed.
GPS receiver
This is a radio receiving device that determines the coordinates of the location of the antenna, based on information about the time delays of radio signals from 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 models have an accuracy of one hundred and fifty meters, and on new ones, up to three meters.
Based on the receivers, GPS loggers, GPS trackers and GPS navigators are made.
The equipment can be custom and professional. The second is distinguished by quality, operating modes, frequencies, navigation systems and price.
User receivers are able to report the exact coordinates, time, altitude, direction set by the user, current speed, information about the road. Information is displayed on the phone or computer to which the device is connected.
GPS navigators: maps
Maps enhance the quality of the navigator. They are vector and raster types.
Vector versions store data about objects, coordinates, and other information. They can include a characteristic of the natural type of terrain and many objects, for example, hotels, gas stations, restaurants, etc., since they do not contain images, take up less space and work faster.
Raster types are the simplest. They are an image of the area in geographical coordinates. A satellite photograph can be taken or a paper type card scanned.
Currently, there are navigation systems that the user can supplement with their objects.
GPS trackers
Such a radio receiving device receives and transmits data for monitoring and tracking 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 who is at a distance.
GPS trackers are:
- personal, used individually;
- automobile, connected to the on-board car network.
They are used to determine the location of various objects (people, vehicles, animals, goods, and so on).
Against these devices can be used means of suppressing signals that form interference at those frequencies where the tracker works.
GPS logger
These radios are capable of working in two modes:
- regular GPS receiver;
- logger, recording in memory the information about the path that has been traveled.
They can be:
- portable, equipped with a small battery;
- car powered by the onboard network.
In modern models of loggers, it is possible to record up to two hundred thousand points. It is also suggested that you mark any points in your path.
The devices are actively used in tourism, sports, tracking, cartography, surveying 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 has a tendency to even wider distribution.
Global positioning covers consumption. Using the latest technical innovations makes the system one of the most popular 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 flaws. For example, in an apartment in a reinforced concrete building, in a tunnel or basement, it is impossible to determine the exact location. Magnetic storms and radio sources located on the ground can interfere with normal reception. Navigation maps quickly become obsolete.
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 at all. Therefore, it is so important that in addition to the global positioning system GPS and GLONASS, and Galileo are also developing.