The key to this jump is landing as high as possible on the back side of the tabletop.
The higher you land, the more speed you will retain. Approach the initial ramp straight-on
- don't hit the ramp at an angle. However, you should be looking sideways and sprinting as
you go up the ramps. While you are in the air after the first ramp, you
may want to release forward and use the left/right strafe keys to position your landing.
Also, going from wall to wall during the time you are airborne (by accelerating
in midair) will make you gain
horizontal speed, which can be converted to height off the last ramp.