Okay, so I asked a question a while back about flying over a cliff and whether the Inspire would suddenly drop in altitude.  The response was, in simple terms, "no".

However, I failed to ask (and don't recall if someone mentioned) what happens if you descend after flying out past the ledge?  Recently I flew out from the top of a water fall and wanted to descend once downstream.  But I noticed my altitude was still indicating I was around 15 ft above ground level.  To descend near to the base I would have pushed it down about 30 ft or more.  My theory was it would fly normally, but my fear was it would think it should be landing and shut down the motors.

Was my concern unfounded?

Yeah, I've flown from parking decks to the street below.  The altitude goes negative.  The craft does not think it's landing.  I had no issues but it was kind of odd seeing the negative altitude.

The altidtude entering negative teritory, and flying normal...my best around -115 m , still perfectly normal to control

Displayed altitude can be influenced by different  weather condition, also IMU calibration should solve this issue