Leveling subfloor for hardwood

This winter I cut down two massive Norway Maples. The trunks went off to the mill and I had them cut, kiln dried, and milled T&G for flooring. I pulled the carpet up in my house today knowing I would have to do some leveling, but I didn't expect this much. It has a significant peak in the middle. Using a rotating laser level, I measured down to the highest point (which is about on the 2/3rds point in the room) and got 17.25". From there it all goes downhill.... literally.

I'll try to...

Leveling subfloor for hardwood