Not exactly "flying" up the hill but pretty cool otherwise. Is this GPS assisted or purely cameras/lidar?

LIDAR?
http://en.wikipedia.org/wiki/Lidar

Nothing new here. It's just good old-fashioned lidar: http://en.wikipedia.org/wiki/LIDAR

^
From NASA site

The scientific goals of LIDAR are to:

* Study the evolution of aerosols and stratification of the atmosphere, as well as acquire meteorological and environmental information
* Provide measurements of atmospheric parameters not attainable by other techniques, such as the structure of the near-surface boundary layer and the dynamic of its scattering properties (this is actually the instrument's main objective)
* Measure the daily and seasonal variability and the vertical structure of the Martian atmosphere
* Detect cloud and fog appearances
* Measure incoming solar radiation and its correlation with atmospheric turbidity
* Measure the depolarization factor of the sky emission

Comment hidden because you are ignoring dag. (show it anyway)

What are they using the LIDAR for on the Phoenix?

AWESOME! The LIDAR at the end is great! The head of the physics department at Dalhousie University Tom Duck was involved with that project. They often use the LIDAR from campus in Halifax. You can see it in the sky all around town. This green laser shooting up from Dal.