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2/1/2022 10:15 AM
 

I had a few questions about the GPX file and I was wondering if someone could help me answer them.

  • If I have it connected to a Stratus/Stratux, which provides a WAAS GPS source, will it always write that position to the GPX file (vs.using the phone's less accurate GPS)? On a related note, this might be a nice thing to add to the file - source.
  • Is there a way to change it so that it shows elevation above the ground instead of MSL?
  • I noticed that the intervals between points are not consistent. Sometimes there are multiple per second and other times there are 5+ seconds between points. Is anyone else seeing this or is it just me? Is this caused by losing GPS signal? What should the interval be?

Thank you all in advance.

 
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2/1/2022 3:50 PM
 

iFly records whichever GPS source it's using to drive the moving map.  By default, it prefers any external GPS, so if you're connected to an ADSB receiver it'll consume the GPS from that device.  (There is a way to override that behavior and force iFly to use the internal GPS of the phone or tablet device it's running on, but I always forget how to do that because I never use it.)

I'll let Brolin or someone else from iFly answer your questions re: MSL vs. AGL altitude and the recording interval.

 

 

 
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2/1/2022 7:03 PM
 

It would seem that unless you were flying "Nap Of The Earth" and wanted to see how well you were maintaining a precise level AGL, AGL would be relatively useless, as it would be (depending on the precision of the base map) constantly changing. 

I'm not from iFly/AP though.

 

 
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2/2/2022 11:13 AM
 
Fred wrote:

I had a few questions about the GPX file and I was wondering if someone could help me answer them.

  • If I have it connected to a Stratus/Stratux, which provides a WAAS GPS source, will it always write that position to the GPX file (vs.using the phone's less accurate GPS)? On a related note, this might be a nice thing to add to the file - source.
  • Is there a way to change it so that it shows elevation above the ground instead of MSL?
  • I noticed that the intervals between points are not consistent. Sometimes there are multiple per second and other times there are 5+ seconds between points. Is anyone else seeing this or is it just me? Is this caused by losing GPS signal? What should the interval be?

Thank you all in advance.

I'll forward this on to my devs to get better answers, but 
1. Yes cobra is right. it's however you're receiving data to start with. if you have a stratus or integral gps. we obviously prefer an adsb receiver though.
2. It will always be AGL as it's GPS derived. I could be wrong on this, so asking for clarification.
3. I don't know this one, I can speculate to say that it could be hearbeats from an adsb receiver, but not entirely sure. Again, deferring to whatever the devs say.

 
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2/2/2022 11:33 AM
 

Checked with Walter, and 1 and 2 are correct. Here's some more info on 3...

We only log a new data point if there is a change in speed, direction, or altitude. Theoretically if you were straight and level for 30 minutes there would be a point at the start and a point at the end. Conversely, if you were off doing aerobatics there would be a ton of data points. 

Hope this helps!

 
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