Fuji,
"non baro aided outages" means outages based purely on satellite constellation data. Eg the prediction algorithm has not used barometric data.
The use of barometric data will reduce periods of outages.
GPS receivers run something called a Kalman filter. For the vertical channel a GPS can use barometric altitude as an input to the kalman filter. Theoretically this will give a smoothed and more accurate calculation of altitude. Also if a satellite is lost (4 to 3) a 3D solution will still be possible when the GPS is baro-aided although it will be a degraded position/velocity solution.
Cheers
JP1