What is global positioning?

Today, probably, there is no person who would not have heard of GPS. However, not everyone has a full understanding of what it is. In this article, let's try to understand 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 functioning in the US Department of Defense. The project was launched in 1973. And already in the beginning of 1978, after successful testing, they were put into operation. By 1993, 24 satellites were launched around the Earth, completely covering the surface of our planet. The civil part of Navstar's military network was called GPS, which means Global Positoning System ("global positioning system").

Its base consists of satellites that move along six circular trajectories of the orbit. In width they are only one and a half meters, and in length - a little more than five. Weight at the same time is about eight hundred forty kilograms. All of them provide full working capacity anywhere in the world.

Tracking is carried out from the main control station, located in the state of Colorado. There is the base of the Air Force Shriver - the fiftieth space connection.

On Earth there are more than ten stations intended for tracking. They are on the island of Ascension, 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. Loading of data with amendments is done every twenty-four hours.

Such global positioning is a satellite system operated by the United States Department of Defense. It works in all weathers and constantly transmits information.

Principle of operation

Global positioning systems GPS operate on the basis of the following components:

• Trilateration of the satellite;
• Satellite ranging;
• Accurate time reference;
• Location;
• correction.

Let us consider them in more detail.

Trilateration is understood as 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.

Dalmetry means the distance to the satellites, counted by the time of passing 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, due 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 clock. The satellites employ an atomic clock, the accuracy of which is up to one nanosecond. However, because of the 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 necessary for stable movement in orbit and a narrowing of the resistance of the atmosphere.

When the global positioning system works, mistakes are made in the world that are difficult to remove. This is due to the passage of the signal through the troposphere and the ionosphere, where the speed decreases, which leads to malfunctions in the measurements.

Components of the cartographic system

There are many products of the global positioning system and GIS applications for mapping. Thanks to them, geographic data is quickly formed and updated. Components of these products are GPS-receivers, software and data storage.

Receivers are able to do calculations with a frequency of less than a second and accuracy from tens of centimeters to five meters, functioning in a differential mode. They differ in size, memory size and number of tracking channels.

While a person is standing in one place or moving, the receiver receives signals from satellites and calculates its location. Results in the form of coordinates are displayed on the display.

Controllers are portable computers that operate under the control of software required for data collection. The software monitors the receiver settings. The drives have different sizes and types of data recording.

Each system is equipped with software. After you download 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 the data. Some of them can be edited in manual mode, others can be printed and so on.

GPS global positioning - systems that facilitate the collection of information for input into databases, and the software exports them to GIS programs.

Differential correction

This method significantly improves the accuracy of the data collected. At the same time, one of the receivers is at the point of certain coordinates, and the other collects information where they are unknown.

Differential correction is realized in two ways.

• The first is a differential correction in real time, where the errors of each satellite are calculated and reported by the main station. Refined data is perceived by the mobile receiver, which shows the corrected data.
• The second - differential correction in postprocessing - takes place when the main station writes corrections directly to the file in the computer. The original file is processed along with the refined, then we get a differentially adjusted one.

Trimble mapping systems are able to use both methods. Thus, if the mode is interrupted in real time, then it remains possible to use it in postprocessing.

Application

GPS are used in different areas. For example, global positioning systems in the field are widely used in 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, where traffic flows and the municipal system are controlled.

A wide application of the GPS-system of global positioning was obtained in agriculture, describing, for example, the characteristics of fields. In the social sciences, historians and archaeologists use them to navigate and register historical sites.

The scope of GPS mapping systems is not exhausted by this. They can be used in any other applications where exact coordinates, time and other information are needed.

GPS Receiver

This radio receiver, which determines the coordinates of the location of the antenna, based on information about the time delays of radio signals from the satellites Navstar.

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. GPS-navigators of commercial type on old samples have accuracy from one hundred and fifty meters, and on new ones - up to three meters.

Based on receivers, GPS-loggers, GPS-trackers and GPS-navigators are manufactured.

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 provide accurate coordinates, time, altitude, user-specified direction, current speed, road information. The information is displayed on the phone or the computer to which the device is connected.

GPS-navigators: maps

Maps improve the quality of the navigator. They are of vector and raster types.

In vector variants, data about objects, coordinates and other information are stored. They can include a characteristic of a natural type and a lot of objects, for example, hotels, gas stations, restaurants, etc., because they do not contain images, take up less space and work faster.

Raster types are the simplest. They represent an image of the terrain by geographical coordinates. A photograph can be taken from a satellite 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 for monitoring and tracking the movements of the various objects to which it is attached. It includes a receiver that determines the coordinates, and a transmitter that sends them to the user who is in the distance.

GPS-trackers can be:

• Personal, used individually;
• Automotive, connected to the onboard network.

They are used to determine the location of various objects (people, transport, animals, goods and so on).

Against these devices can be used to suppress signals that form interference at those frequencies where the tracker operates.

GPS Logger

These radios are capable of operating in two modes:

• Conventional GPS-receiver;
• Logger, writing in memory information about the path that was passed.

They may be:

• Portable, equipped with a small battery;
• Automobile, powered by an on-board network.

In modern models of loggers, it is possible to write up to two hundred thousand points. Also it is suggested to mark any points on the way.

Devices are actively used in tourism, sports, tracking, cartography, geodesy and so on.

Global positioning today

On the basis of the above information, it can be concluded that such systems are already in use everywhere, and the scope of application tends to be even more widespread.

Global positioning covers the sphere of consumption. Using the latest technical innovations makes the system one of the most popular on this segment of the market.

Along with GPS in Russia, GLONASS is being developed, in Europe - Galileo.

At the same time, global positioning is not without its shortcomings. For example, in an apartment of 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 cards 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, include interference or disable 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.