I'm working on a fire safety training app build in AR (Augmented Reality) using Unity and Vuforia* .

The users will be wearing Google Cardboard* headsets (but able to view reality around them through a cutout). They are able to see "virtual machinery" which catches "virtual fires" - and they need to extinguish them using the correct fire extinguisher.

They will pick up a physical (dummy) fire extinguisher and by pressing a button on the extinguisher and pointing it's nozzle in the correct direction:

  1. If it is pointed in the direction of the fire and held for 'x' seconds, it should put the fire out (key feature).
  2. I need to show "extinguishing foam / material" come out from the nozzle as viewed by the user through the headset (nice to have feature).

My challenge is how can I determine where the "nozzle" of the fire extinguisher is pointed to with respect to the room or with respect to the headset. I can place beacons at fixed points in the room, but I'm not sure which products will allow me to determine the position / orientation of the nozzle.

To my understanding, there are "controllers" available for smartphone-headsets, but they communicate only button presses - not their own position with respect to the smartphone.

Any innovative / unconventional ideas on how to solve this? :)

*(if another low cost hardware/software platform supports this, I would be open to change)


If you are up for programming this device yourself stick a Hexiwear on the nozzle. Or you can make something similar and cheaper but bulkier with ESP32 and some sensor modules. But be warned that this will require a lot of research and programming.

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  • Thanks @jan Dorniak for sharing this info - is this something that will allow me to determine the distance between it and the smartphone? Looking at the sensors list, I don't think it could. – siliconpi Sep 26 '19 at 8:49
  • @siliconpi it certainly can detect the right direction. I don't think distance relative to the smartphone is actually possible. Subconsciously I read "position" mostly as the direction the nozzle is pointed to. IFF the nozzle is in view of your camera you could probably just rely on visual recognition after sticking some of those visual beacons on it. If the nozzle is off camera distance could in theory be measured with radio time-of-flight solutions but that requires specialized hardware on both ends. And I don't know if they are precise enough to be used at such a small scale. – Jan Dorniak Sep 26 '19 at 9:01
  • Also see this: electronics.stackexchange.com/a/460305/95142 - most likely you would have to rely on visual recognition when the user picks up the dummy extinguisher to position it and then inertial navigation later on when they are handling it. At least that's a quick solution which comes to mind right now. – Jan Dorniak Sep 26 '19 at 9:06

Take a look at BLE 5.1, which supports AoD/AoA and will let you locate someone, both direction and distance, to within one metre.

Read this for more info.

The nRF52811 SoC’s Bluetooth 5.1 Direction Finding enables positioning solutions to not only rely just on received signal strength indicator (RSSI), but also the actual direction of a signal. This improves accuracy significantly and opens up new applications. There are two types of methods for determining direction, angle of arrival (AoA), where the direction of the received signal is calculated, and angle of departure (AoD), where the direction of the transmitted signal is calculated. Direction finding can operate in either two or three dimensions depending on the selected design complexity and antenna array. The nRF52811 SoC is the ideal choice as a transceiver for both the AoA or AoD scenarios. Bluetooth 5.1 hardware functionality is built-in to the nRF52811 SoC.

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