The people being relocated are the ones who lived in the lowlands right along the dammed rivers. I’m curious about what assumptions the researchers made about population distribution farther away from those rivers.
In any case, I’d be willing to bet that every human on earth has been observed and counted by satellites by now, with the possible exceptions of those few who remain indoors or underground at all times, and I wouldn’t even be too sure about them.
Only if the satellites can avoid recounting on subsequent passes. In short, they can't help with this.