We frequently hear that "morale is bad," or words to that effect, usually during some significant organizational change initiative.
Is it really bad? If so, does it matter? In fact, do we really care??
Most importantly, morale shouldn't be the focus. Morale, in and of itself, is a non-starter. Instead, focus on observable behaviors demonstrated in the workplace.
Is there really a substantial behavior/performance issue, or just normal, elevated apprehension that accompanies all extensive change efforts?
If there ARE behavior/performance issues, identify and concentrate on those that are actionable -- that can be directly modified.
If you really feel the need for a current "pulse," and your managers aren't credible enough to get it by walking around and having conversations, then consider a select few representative focus groups. These allow follow-up questions not easily available with formal surveys.
Pay attention, keep your ear to the ground, and don't confuse predictable grumbling about change with real differences in performance or behavior.
But that's just me...