Is it just me or I have been experiencing this for awhile that my altitude on the panel of any aircraft i go to seems to be always wrong and unrealistic. Air traffic controllers often tell me that my altitude is different from what theirs say! Sometimes my panel shows i am at 5000 feet for example but I am actually at 11000 feet! So while using the auto pilot I sometimes have to cope with it and try putting the altitude lower! Sometimes the HUD screen that only some planes have, also tell me my real altitude compared to the wrong ones on the panel. But planes that do not have the HUD screen, I cant seem to figure out my real altitude and I can't fly normally. I have read up and tried pressing B but did not change anything on the panel. And also what is the difference between BARO and RADAR, radar seems to be a lower altitude?