Hi All (been a while)

I have been asked to look into developing an application that will allow and administrator to map out a large factory floor.
In essence they want something like Google maps where the user can see where they are and add tags to certain locations. The problem of course is that these mapping apps google/bing don't show interiors.

All i really need to so is to draw an outline of the factory floor on a map and add these tags but I have never touched on this subject before.

Has anyone done anything similar and if so can you give me any tips before I dive into this?