Can an indoor positioning system work outdoors? – Yes, of course!
There is no fundamental difference between indoor and outdoor local positioning systems. They use the same architectures and even very similar beacons. For example, Indoor positioning system for archaeology.
But there are essential details that have to be taken into account.
The most significant difference between indoor and outdoor is in the environmental conditions. Indoor is typically an office and warehouse/factory-like environment – reasonable 10…40C, no rain, no moisture, no dust, i.e., no special protection is required for the equipment.
Outdoor can be significantly harsher:
So, depending on the conditions, different protection methods shall be applied. They may affect performance (weight, size, power consumption, etc.) and almost always involve costs.
Be very vigilant about IPxx marks, for example, IP67. It is a significant mark where:
Impressive, right? Well, there is a fine print. The test says that when such conditions are applied, the device must withstand them and not be killed. The IP67 guarantee that the system will work in those conditions.
There is even more fine print:
Thus, when the IPxx mark is seen, it shall be interpreted and used with all underlying assumptions, and often those assumptions are not applicable in real life.
Therefore, environmental conditions are the most challenging part of the outdoor local positioning system.
It is relatively easy to get a power supply for stationary beacons indoors: regular power grid + converters, unprotected batteries, PoE – many options. See more: Power supply options for beacons.
It is more difficult outdoors:
Wind can affect ultrasound-based systems in two ways, at least:
Luckily, these factors are not severe unless the wind is strong.
Drops of rain produce noise similar to ultrasound pulses. Thus, it is crucial to protect ultrasound-receiving beacons from the noise produced by the drops. All kinds of special shields and umbrellas usually do the job well.
Typically, an outdoor is an open space. Covering the same territory with a fraction of stationary beacons required indoors is possible.
It is possible to do sensor fusion with GNSS systems, for example, GPS or RTK GPS, for the best performance.