Technology is at the heart of society now and constantly evolving to help us live in an easier, safer and more convenient way. While the internet might be the biggest overall tech development in recent history, things like smart appliances and mobile phones also rank highly. Another stunning tech breakthrough we have seen over the last few decades is GPS. But what is it and why can getting a GPS signal indoors be tricky in most buildings?
Before we look at why GPS technology does not work in some buildings, it is worth pinning down what it actually is. This will not only make it easier to understand but also easier to see why it does not work in some places.
The Global Positioning System (GPS) was developed to allow accurate determination of geographical locations by military and, later, civil users. It is based on the use of satellites in Earth orbit that transmit information which allows satellite receivers to measure the distance between the satellites and the user.
Satellite receivers use the information to determine their location by calculating longitude, latitude and altitude from the received signals.
Once the GPS receiver in your device calculates its distance from 4 or more of these satellites, it can indicate your exact location.
The GPS consists of 24 in-use satellites (with spares) and is owned and operated by the United States government. GPS is one example of several Global Navigation Satellite Systems (GNSS) in use today.
A key thing to note is that signals reaching the receiver in your GPS device are very weak, having travelled some 12,500 miles down through the atmosphere from the satellites.
Consequently, GPS signals are unable to pass through dense materials such as concrete, heavy wood or steel cladding. To get the best effects from GPS tech, you really need visibility of a large area of sky to ensure that the received signal is strong enough pinpoint your location with any degree of accuracy.
Bear in mind that GPS was originally never intended to be used indoors. It was first conceived of in 1973 and provided a means to help military submarines navigate when on the surface.
The publicly accessible GPS as we know it today became operational in 1993.
Without clear visibility of at least four satellites, it is usually impossible to achieve and maintain a positional fix when indoors, using “native” GPS signals from the orbiting satellite constellations.
There are several proprietary systems that can pinpoint indoor locations by using WiFi, cellular and Bluetooth systems.
A GPS repeater system brings the outdoor signal inside to allow GPS-enabled devices to be used, tested, repaired and calibrated inside any building or space where it is usually impossible.
A repeater can provide coverage over a large indoor area. For example, when installed in the ceiling of a hangar, at a height of 10 meters, the coverage area below will be approximately 35 meters in diameter.
Applications for such a system are many and varied, including emergency services (blue light) premises, vehicle assembly lines, underground bus/rail stations and aircraft hangars.
In these applications, extreme positional accuracy is not the main requirement.
In a fire station or a police station, the requirement is to prevent navigation equipment from going “off grid” when live GPS signal is not available. The repeater eliminates the problem of an extended satellite acquisition delay when exiting the station and ensures that all assets are visible at the command centre.
A repeater in an aircraft hangar allows on-board satellite equipment to be tested without the need to push the aircraft outside to pick up a signal.
When installed within the final stages of a vehicle production line, a repeater brings the outdoor signal inside, reducing delays and increasing productivity – no need to drive a car outside to allow its infotainment system to achieve a GPS fix.
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