GNSS positioning methodology

[Tom Kitto]

I'm looking for a detailed explanation about how the GNSS solution and overall the trajectory is derived for the base and lidar unit in GVI systems by liacquire and ligeoreference. The GVI-advised process appears to be calculating a PPP solution for both (let the base log for 30-40 mins before flying, let the lidar unit log for 5 mins before flying) - I find this a bit confusing as to why we'd need to set up a base if the solution is PPP - this GNSS methodology only requires one antenna to derive a solution. 

I'm asking this in order to be able to advise my clients on the most efficient field survey methodology.