I could swear that I've heard of a software like this, I pray it's freeware, and I'm sorry if someone has asked something just like this already.

I'm trying to make an interactive map... not sure if interactive is the right word. I am sure there is one and I'm just not thinking of it but... What I mean is that I would like to be able to navigate my map in a software that calculates the distances between things for me. (One that takes into account that my flat map is actually a globe..) I'm trying to make truly world sized maps out of my originals, possibly using the original images as bases to build onto.

It would be nice to be able to zoom into a location and add more details, towns etc...

Any recommendations?