"john smith" wrote in message
...
The regs say you must communicate, have permission, a clearance, have a
transponder, etc to fly in any Class B/C/D Airspace.
The airspace is generally defined by the airport reference point altitude
and location on the field. For example the definitions state "from the
surface to..."

The airspace isn't defined by reference to the airport altitude. An airspace
that goes down to the surface goes down to the surface at each point in that
airspace; otherwise, it would say e.g. "airport elevation to 2600" rather
than "surface to 2600".

--Gary