"David Megginson" wrote in message
...

You are supposed to be flying at your planned altitude. I don't know
how far ATC would be willing to trust that, though -- you'd certainly
be within your rights to choose a different altitude to avoid
turbulence or icing.


Where are those rights found?



How good a job can primary surveillance radar do on picking out a
target's altitude?


It can't do that job at all.