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What is the difference between calibrated altitude and GPS altitude?
Indicated altitude is pressure altitude corrected for local atmospheric conditions. All aircraft in a given area should be on the same altimeter setting so relative (altitude) separation is maintained. A GPS, on the other hand, measures your absolute altitude off several satellites.
How does a transponder report altitude?
The transponder can get its information from one of two sources: an encoding altimeter, which transmits a pressure altitude reading to the transponder, or — more commonly — a blind encoder, an altimeter without needles or adjustment knob permanently set to 29.92 (pressure altitude).
Is GPS accurate for altitude?
If a decent signal reception is available, a modern GPS receiver should be able to give elevation data accurate to a range of 10 to 20 meters (35 to 70 feet) post correction. And that’s exactly where the problem with GPS-based altimeter watches meant for the great outdoors lies.
What is Mode C altitude?
While the primary function of secondary surveillance radar (SSR) is to detect and identify aircraft, the radar response from the aircraft may also be encoded to indicate the aircraft altitude. This capability is known as Mode C and will indicate the aircraft pressure altitude at intervals of the closest 100ft.
How high up are GPS satellites?
approximately 20,200 km
GPS satellites fly in medium Earth orbit (MEO) at an altitude of approximately 20,200 km (12,550 miles). Each satellite circles the Earth twice a day.
How does a mode C transponder get its altitude?
The transponder depends on an external altitude encoder to provide the digitized pressure altitude that the transponder needs for its Mode C replies. The encoder is connected the same static air line as the altimeter and is wired electrically to the transponder.
Why is my transponder telling me I am at the wrong altitude?
If your panel altimeter checked out, you used the proper setting during the approach, and your transponder is telling them you are at the wrong altitude the transponder’s altimeter appears to be the problem. I’m no expert, but from what I gather the transponder has a direct connection to the altimeter pre -Kollsman window.
Do you need an altimeter to report altitude?
Back at the hangar, the question is: does the aircraft have or need an encoding altimeter interfaced to the transponder to report altitude, is it built into some transponders; or was the Approach controller using altitude as reported by the radar if it has height finding capabilities?
Can a transponder be set to 29.92 while in flight?
Easy fix. Since the transponder is working off of pressure altitude you should be able to set your altimeter to 29.92 while in flight and your altimeter and transponder altitude should be the same to see if you have a calibration error between the two. (You must log in or sign up to reply here.)