Use particle board over wood plank flooring to smooth it out for laminate flooring

If your subfloor is only a 1/2 inch thick and partially rotten you need to replace it. Even if it were in perfect condition that's not thick enough for laminate flooring, it will droop and bounce like walking on sponge cake. Cut out your floor boards, true up/replace/sister your floor joists using a site laser or string line and power plane if they need it (and I'd bet you a shiny nickel they do)especially if the joists are under the span load limit, here's a tutorial on span limits: http://www.awc.org/technical/spantables/tutorial.php It looks daunting but its not as bad as it looks. If you're still fuzzy just go to your local building center and they can usually calculate loads and spans for you. Once you've got that figured out, sheet with 3/4 t&g cdx. Run a bead of PL on the joists to fill and small voids and bind it all together. Here's a pretty thorough link from a sheeting manufacturer. http://buildgp.com/wood-products-installation-tips Hope this helps!

• Lie down and eyeball it. It's easier to see if you are right down on the surface. Someone in the business of laying floors might have developed a better eye than you (if they miss it, it costs them money) and not need to lie down.
• Shoot a laser pointer across the floor - either skim the surface looking for discontinuities, or lay it on the floor and check its height with a ruler as it goes across the room. Easier if you can get the start and end adjusted to the same height. A hump will be a place where the beam height above the floor reduces; &/or where the beam won't make it across the whole room if it's right down at floor level.
• Choose a long straight board, and set it on edge on the floor. If you find a place where it rocks from end to end, that's a hump. Check that the board is really straight by making sure it rocks about the same on both edges (a warped board will rock on one edge, not on the other - a straight board on a hump will rock on both edges)

If you want to install a wood floor over a hump, wood parquet can be much more forgiving. I don't know if the laminate folks have entered that market, but it can be quite affordable in real wood.