Mapping in a GPS Denied Environment

I have a customer looking for options on accurately mapping in a GPS denied environment.
Construction project: wet well pump station.
It would have to be inertia and dead reckoning (my opinion)
I see something along the lines of Elios with a measuring capability.
I don’t think that system outline exists in a production drone package.
Any experience that would suggest differently?

Where are you?

GPS denied? Please explain.


Underground waste water treatment facility.

Customer looking for vault inspection options.

CM level accuracy



Ok, so not necessarily GPS-denied, but unavailable? I would try Microsoft ICE. It is a powerful and free stitching program that can take just about any set of tiled images and make an orthomosaic. It will not be measurable, but will give you the big picture. This is how I make my 360-degree panoramas.