Nexrad data mislocated on display? - iFly Owners Q&A

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Nexrad data mislocated on display?

7/4/2013 3:16 PM

srf

Joined: 4/6/2012

Posts: 3

Nexrad data mislocated on display?

On two occasions now, I have been suspicious that the Nexrad returns are not located correctly on my iFly 720.
Here is what makes me suspicious:

1. On 6/22/13, I was travelling west thru Ohio to KHHG in Indiana, and approaching some convection storms. I have a Skyradar receiver, which is Wifi connection to the iFly, and also connected to a tablet computer via a USB cable. So, both devices were receiving the same ADS-B data. The Nexrad returns had the same shape on the two different devices. However, the iFly 720 showed the location roughly 20 miles south of the location shown on the table computer (running Essential Flight). The view through the windshield suggested that the iFly display was not correct.

2. On 7/4/13, I was using the same equipment, and experienced the same discrepancy of Nexrad return location between the two different displays, with the iFly 720 showing the returns roughly 20 to 30 miles south of the tablet computer. I was not close enough to compare my view thru the windshield. However, after landing I pulled up Nexrad on DUAT on my phone, and it suggested that the iFly display was mislocated.

I am having trouble making sense of this, and wonder if I am the only one who has experienced it.

7/5/2013 3:35 PM

Donald Alexander

Joined: 4/14/2013

Posts: 31

Re: Nexrad data mislocated on display?

That's interesting. On 6/23/13 I was using the iFly with ADS-B (Sky Radar D2, if it matters) and I was tracking convective cells from NY to VA. I was surprised to see how much further north the cells were that I expected. It never occurred to me the iFly wasn't displaying NEXRAD correctly. It was my assumption that the delay in getting the NEXRAD mosaic broadcast was what caused the "off-set". I'll pay more attention in the future.

7/5/2013 5:17 PM

Walter

Joined: 7/8/2009

Posts: 2778

Re: Nexrad data mislocated on display?

These are the first reports we've heard on a possible issue with Nexrad data being shown at the incorrect location. I have logged this as a high priority issue and we'll do further research. Our tests, both internally and on the field, have never noted this problem. More to come on this...

Thanks,
Walter

Walter Boyd
President, Adventure Pilot

7/8/2013 4:57 PM

Donald Alexander

Joined: 4/14/2013

Posts: 31

Re: Nexrad data mislocated on display?

Walter, Just to be clear, I didn't have any other devices running to compare with my NEXRAD radar on the iFly. As a result, I don't know that there was an offset. Most of the weather from Canada south that day had been moving slowly. When I got to southern NY/northern NJ I simply noticed the view out the cockpit was not what I expected. I don't think it was off 20-30 nm - (maybe half that) but with slow moving weather it was unexpected. An off-set would have explained what I was seeing and so would have a longer delay in broadcasting NEXRAD or an increase in the speed of the weather. I simple don't know and am being aware of all the possibilities.

The big thing it pointed out to me is what NEXRAD is good for and what it isn't good for. I'll go around weather but I won't try and shoot a gap in the weather...at least not one that I can't verify visually. It's a wonderful tool but it isn't the same as having radar on board.

Don

7/9/2013 8:47 AM

Walter

Joined: 7/8/2009

Posts: 2778

Re: Nexrad data mislocated on display?

You guys were right. We found some code that could sometimes lead to a scale issue when rendering the nexrad image, which would cause the storms located toward the outer portions of the coverage area to be off. This has been fixed and a new beta version has been released. This will be moved to production soon, this week hopefully - next week for sure.

Thanks for reporting this!

Walter

Walter Boyd
President, Adventure Pilot

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Nexrad data mislocated on display?

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