Global Positioning System (GPS) and How It Works

Global Positioning System (GPS) and How It Works

Global Positioning System (GPS)

Global Positioning System (GPS) is a system for determining the position on the earth's surface with the help of satellite signal synchronization. This system uses 24 satellites that send microwave signals to Earth. This signal is received by the receiver on the surface and is used to determine the location, speed, direction, and time.

This system was developed by the United States Department of Defense, with the full name being NAVSTAR GPS (a common mistake is that NAVSTAR is an acronym, this is wrong, NAVSTAR is the name given by John Walsh, an important policymaker in the GPS program). This collection of satellites is maintained by the United States Air Force's 50th Space Wing. Maintenance costs for this system are approximately US $ 750 million per year, including replacement of old satellites and research and development.

GPS Tracker

GPS Tracker or often referred to as GPS Tracking is an AVL (Automated Vehicle Locator) technology that allows users to track the position of vehicles, fleets, or cars in Real-Time. GPS Tracking utilizes a combination of GSM and GPS technology to determine the coordinates of an object, then translate it into a digital map.

Procedure

This system uses several satellites in earth orbit, transmitting the signal to the earth, and is picked up by a receiver. There are three important parts of this system, namely the control part, the space part, and the user part.

1. Control Section

As the name suggests, this part is for control. Each satellite can be slightly out of orbit, so this section tracks the satellite's orbit, location, altitude, and speed. The signals from the satellites are received by the control section, corrected, and sent back to the satellite. Correction of precise location data from these satellites is called ephemeris data, which will then be sent to our navigation equipment.

2. Space Section

This section consists of a collection of satellites that are in Earth orbit, about 12.000 miles above the earth's surface. This collection of satellites is arranged in such a way that the navigation device can receive signals from at least four satellites at any time. These satellite signals can pass through clouds, glass, or plastic, but not buildings or mountains. 

Satellites have atomic clocks, and will also transmit this time clock information. This data is transmitted with a pseudo-random code. Each satellite has its own code. This code number will usually be displayed on the navigation tool, so we can identify the satellite signal that is being received by the tool. 

This data is useful for navigation tools to measure the distance between the navigation tool and the satellite, which will be used to measure the coordinates of the location. The satellite signal strength will also help the tool in calculating. The strength of this signal is more influenced by the location of the satellite, a device will receive a stronger signal from the satellite directly above it (think of a satellite location such as the position of the sun at 12 noon) compared to a satellite that is on the horizon line.

There are two types of waves currently used for satellite-based navigation tools in general, the first is better known as L1 at 1575.42 Mhz. This L1 signal will be received by the navigation tool. The satellite also emits L2 waves at a frequency of 1227.6 Mhz. This L2 wave is used for military purposes and not for the public. 

3. User Section

This section consists of the navigation tools used. The satellites will transmit almanac and ephemeris data which will be received by navigation tools. Almanac data contains the approximate location of the satellite that is broadcast continuously by the satellite. Ephemeris data are transmitted by satellites and are valid for about 4-6 hours.

To show the coordinates of a point (two dimensions), navigation tools need at least a signal from 3 satellites. To show the height of a point (three-dimensional), an additional signal from one more satellite is required.

From the signals emitted by a collection of satellites, the navigation tool will perform calculations and the final result is the coordinates of the position of the tool. The more number of satellite signals received by a device, the tool will calculate the coordinates of its position more precisely.