Here at Chronos, we have considerable experience of taking GPS signals indoors. That includes within military and civil aviation hangars. The use case here is to enable routine test and maintenance tasks that require the use of the aircraft’s GNSS systems without the need to roll the aircraft out of the hangar for a sky-view. The business case is a compelling one. Moving a jet fighter in and out of the hangar just for testing is very time and resource heavy.
These systems also only require a valid GPS/GNSS signal. The fact that they will be receiving the location of an external antenna rather than the actual aircraft location is not an issue here.
Indoor GPS/GNSS Pitfalls
Another use case we have seen is to maintain GPS readiness of a vehicle parked inside. Specifically, so there is no delay in acquiring satellite signals when mobilising in an emergency. Again, repeating the external antenna position is adequate for this use case. Once outside, the onboard GPS receiver will quickly resolve this small position shift without adverse effects.
Although GPS signals are weak and find it difficult to penetrate buildings there is no certainty that this is the case. Inappropriate use of Indoor GPS will at best bring you to the attention of national spectrum licensing authorities. At worst, it will create real problems for you and others.
We have seen this first hand in an airport repeating system we supplied (but did not install) some years ago that was to ensure fire tenders had a GPS position pending any emergency.
Soon after deploying this system, a runway had an emergency closure as their management system was reporting that a passenger transport vehicle was weaving across the runway. Of course, what was really happening was that a poorly installed repeater was ‘leaking’ GPS signal. The receiver on board the transporter was receiving confusing position data and then reporting an incorrect position that just happened to be on the runway.
Buildings, Car Parks and GNSS
We have had discussions with attraction operators about deploying indoor GPS systems so that the visitor experience can be enhanced using their smartphone and the standard GNSS receiver built in.
There is also a compelling case to use Indoor GPS systems to locate vehicles parked in large car parks and underground car parks.
In both cases, just tread carefully. Your building must not be able to see the satellite signals from the sky, and the surroundings of your building must not see your indoor GPS signals. Test, test and test again before going down the indoor GPS path. You will need a license to transmit these signals in all cases and so you will need to satisfy your national licensing authority that you will not interfere with your surrounding community, and even then a test/pilot scheme would be a prudent first step.
Bluetooth and RF Beacons
Many building use cases are probably best met using Bluetooth to other RF beacons being received either by built in receivers (Bluetooth in a smartphone) or the use of sensors carried by those requiring the navigation service (a car being parked).
For visitor attractions, the Bluetooth iBeacon may well be the prudent solution for navigation.
Summary
The use of Indoor GPS/GNSS is an attractive solution for many situations but you must tread very carefully to make sure that it is right for your building and its surroundings. Prosecution by your national licensing authority is not what we want to achieve here.
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