-9 ft altitude

[lloydr]

Have 71 flights and over 12 hrs flying time. All flights in flight log show altitudes from 25 ft to 400 ft.
But the top altitude on the log shows - 9.8 ft.
Any reason for the top altitude to be negative?

 

[Erised]

The top altitude in the log is not the crafts top altitude above ground level (AGL) but the top altitude (elevation) of your take off point above sea level. Not precise, having a negative is not normal unless your take off point is in Holland or 71 flights by the sea shore, the altitude if often off when you land your craft because the barometer is set upon take off by atmospheric pressure and that may change as you fly from weather or just the days temperatures changing. It also could be just a glitch or you live in Death Valley.

 

[Meta4]

Have 71 flights and over 12 hrs flying time. All flights in flight log show altitudes from 25 ft to 400 ft.
But the top altitude on the log shows - 9.8 ft.
Any reason for the top altitude to be negative?

Two things are happening here.
As Erised mentioned, the Top Altitude is the altitude of your highest takeoff location.
But the other factor is that this number comes from GPS which is terribly inaccurate when it comes to altitude and can easily be 1-200 feet out.
Although the Phantom uses it's barometer for flight data, it uses GPS altitude for the exif data it records with each photo taken.
This one gives you an idea about how (in)accurate GPS altitude data can be.
The relative altitude is the number you see on screen when flying.

 

[RodPad]

Yes, it doesn't look like a submarine.

Rod