@JS1 mentioned in another thread about doing indoor room detection and that got me to thinking....dangerous I know.
I wonder if we could use Volvo's new "Life Paint" to make invisible Glyphs on dark surfaces? We could make a few stencils for each room and then mount a strong LED flash light on our robots to be able to spot the invisible Glyphs with our cameras.
Here's a link to Life Paint
Another way might be to try a strong UV flashlight and use light yellow fluorescent markers to make the glyphs.