You need to have a Spectre and go to blue base. Next, behind the base and up along the rock wall, keep sliding to your right if you're facing the rock wall, or to your left if you're facing the base. Then you will hit a little ramp on the wall where you can ride up. Once you ride up, slide to your left while facing the wall and as soon as you hit the darker rock, you have to boost until you get onto a ledge where you can stand. Ride the Spectre to the invisible wall and get the nose over the edge just slightly so that when you get out you end up on the other side of the invisible wall. Hint: make sure the invisible wall is on the left side of you and your vehicle.