Motion > Directional Modes > View Independent
Gives you full control in defining the forward direction by using the motion bearing and elevation indicators on the Position Control toolbar. You can define different view bearing and elevation values. This gives you the flexibility to move forward in an arbitrary direction while looking in another arbitrary direction.
For example, you could define the motion bearing as 135 degrees and the view bearing as 45 degrees. Moving forward would cause the eye point to move southeast, while looking northeast.
The mouse drag modes, positioning modes, and Position Control toolbar all affect how the directional modes operate.
Click Motion > Directional Modes > View Independent.
You can also click View Independent on the View toolbar.