notchian map files (.mca)

[NiLSPACE]

this is maybe usefull for an converter. i didn't read it (becouse i don't understand anything about what is in that text).
http://wiki.vg/User:Sprenger120

[xoft]

This is actually pretty much known and MCServer already has a MCA file reader (so you can put MCA files into your world folder and it will happily read those files as your world
There are some details that are worth reading, though. Thanks for sharing the link. Since I'll be doing an MCA writer very soon, I'll be studying those very thoroughly