Whilst environmental projector enclosures are ideal for outdoors, a more complex situation is whereby the projector is to be deployed underground. Cave systems and tunnels are examples of such locations.
To be more precise, road traffic tunnels, rail tunnels and tourist attractions such as caves and underground UNESCO sites are locations that have installed protective projector enclosures.
Dust, humidity and sometimes polluted air must be considered in these environments.
Of course with natural locations such as caves, the installation itself brings the challenges of no straight lines, no power, and lack of signal.