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HomeHomeDiscussionsDiscussionsiFly Pictures &...iFly Pictures &...Altitutde Error?Altitutde Error?
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1/28/2011 8:37 PM
 

I have had a chance to use / test my unit on 4 flights (2 round trips, same waypoints). On the first trip, the altitude was off by aprx, 30ft (low) when on the ground and steadily increased to about 375ft (low) when G1000 and steam gauge indicated 6500ft. I spoke with Scott and he suggested I do a full reset to clear the satellite cache which he helped me do.

On the 2nd trip it was near perfect on the ground but off by almost 500ft (low) when compared to the G1000 / steam gauge indicated 6500ft. The altitude on a G1000 / steam are adjusted for pressure so perhaps that is the difference. But if that is the case, how are you using the altitude given by the iFly? I understand that the altitude (on the iFly) is calculated from GPS and is not adjusted for pressure but that still does not help me understand why I would even use this information if it is not remotely accurately when complared to other means of obtaining altitude. I would think that if this were a normal descrepency there would be a way to adjust the altitude on the iFly so it would be usable.

Walter and Scott have been very helpfull. They had the unit picked up and they tested it on their end but they report no problems. I cant imagine that I am the only one that has seen this before but I have been unable to find any posts of this issue. I'm a newbee pilot (and I LOVE the iFly!) so any info is appreciated. Thanks.

Dave


Dave K
 
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1/28/2011 9:48 PM
 

Dave all my GPS,s do the same thing. Unless thay are corrected my pressure. my 396 does the same thing. I talked to Garmin about it they told me that it is because ATC use's the corrected pressure so everybody is off the same amount. But what is displayed un-corrected is closer to absoulute alt. I that makes sense.

Bill Hempel

 
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1/28/2011 9:49 PM
 

P.S. my Ifly is almost exactly what my 396 displays as alt.

 
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1/28/2011 11:12 PM
 

Ok so if all of the GPS based units do this, what relevance is there to having the altitude given if it is not accurate? For example, if I have flight following and ATC expects me at 6500 I cannot rely given GPS altitude as I would be closer to 7000 which ATC would then advise that I am too high.

Like I said - I'm very new to this so please excuse me if I misunderstand but it appears that having conflicting info could pose more of a problem then benefit. Do you use the GPS altitude? If so, for what? Lastly, do you think it would be beneficial to be able to adjust the given GPS altitude to set it inline with the actual altimeter reading (adjusted for pressure)? Thanks.

Dave


Dave K
 
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1/29/2011 12:08 AM
 

That is why we always fly with the barometric altimeter not the GPS altimeter. The GPS altimeter is just an emergency backup. My IFly is sometimes off by 300 to 400 feet but so is my WAAS 530. The WAAS 530 is very accurate at lower altitudes for approaches. Pay attention to the plane's altimeter and use the GPS to get from A to B.

 
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HomeHomeDiscussionsDiscussionsiFly Pictures &...iFly Pictures &...Altitutde Error?Altitutde Error?