I have a condo in a downtown with buildings around 400ft.  In class B Air Space that has 0 height on the AirMap table is this height from the ground or is it based on highest structure in a 400ft radius of the drone?

Ground.          h

NightThunder Posted at 1-9 12:33
Ground.          h

The confusion comes from the height of an object FAA rule within 400ft.  

JohnLietzke Posted at 1-9 12:35
The confusion comes from the height of an object FAA rule within 400ft.

No confusion on AirMap. So I assume you are in a LAANC area (or a proposed one) and are reading the height based on the grid you are in. 0 means that the grid is a "no fly" area and any flight above zero ft is prohibited regardless of the 400 ft rule. It does not apply here. You would need a part 107 waiver.

That is what I thought.  Thanks.

JohnLietzke Posted at 1-9 12:46
That is what I thought.  Thanks.

You are welcome.