Featherweight tracker altitude question

[firemanup]

In reference to the audible call out of apogee altitude during tracking vs the altitude shown in the data file, they are different.

Im assuming the audible just probably lags behind so doesn’t always get the final recorded altitude called out before it starts going into decent rates??

Flight Sunday was called out as 18,200 but the data shows over a 1000 higher. Which one is correct?

Had bad upper level winds, rocket landed 2.5 MILES away in a wheat field, would have never found it without the featherweight, walked me right to it.

 

[Wayco]

I think that the Featherweight GPS calls the altitude from sea level, Is your launch site 1000 ft. about sea level?
Our launch site is, and we get the same results.

 

[firemanup]

I think that the Featherweight GPS calls the altitude from sea level, Is your launch site 1000 ft. about sea level?
Our launch site is, and we get the same results.

Good point, but it appears to be the opposite here for me, audible call out was 18,200’ where the data shows 19,526’ so it appears the call out was AGL and the data is showing nance sea level.

Tks

 

[kjs]

In reference to the audible call out of apogee altitude during tracking vs the altitude shown in the data file, they are different.

Im assuming the audible just probably lags behind so doesn’t always get the final recorded altitude called out before it starts going into decent rates??

Flight Sunday was called out as 18,200 but the data shows over a 1000 higher. Which one is correct?

The data file is the most accurate one. It is saved at 10Hz. The phone only gets packets at 1Hz so can only report on every 10th packet. Also, if it misses packets, it won't know either. I had one that wasn't tracking at peak but picked it up afterwards and so it announced the descending altitude as the apogee.

 

[kjs]

In reference to the audible call out of apogee altitude during tracking vs the altitude shown in the data file, they are different.

Im assuming the audible just probably lags behind so doesn’t always get the final recorded altitude called out before it starts going into decent rates??

Flight Sunday was called out as 18,200 but the data shows over a 1000 higher. Which one is correct?

ah.... Wayco was right - note that the downloaded data is all ASL (Above sea level). The voice calls outs are AGL. if you download the data, you should note the ASL just prior to launch and subtract that off from the apogee values. Your max ASL was 19536 for the phone packets with a launch site altitude of 1248 ASL. that comes out to 18288.

[I thought it odd/wrong that the phone would miss apogee by 1k feet as it is slowing down and should get packets every second or so - usually you get multiple readouts as it approaches apogee and slows down....]

 

[kjs]

I think that the Featherweight GPS calls the altitude from sea level, Is your launch site 1000 ft. about sea level?
Our launch site is, and we get the same results.

The unit should call out altitude in AGL but the downloaded data will be in ASL so needs math to match. We can confirm in a couple weeks...

 

[watheyak]

The unit should call out altitude in AGL but the downloaded data will be in ASL so needs math to match. We can confirm in a couple weeks...

I can confirm this!

 

[firemanup]

I think it did call out AGL.... called out 18,200 and data showed 19,536.

Which would put launch site about 1366 ASL and i think thats right....

Thanks guys...

 

[Buckeye]

The unit should call out altitude in AGL but the downloaded data will be in ASL

As it should be. During the flight, the user needs to know the altitude above ground, while during post-processing of downloaded data, the altitude should be in absolute terms.

As an aside, I wish clubs would be more clear when stating their waiver altitude. Some say ASL, some say AGL, most don't specify either way. This becomes more important west of the Mississippi!!!

 

[Handeman]

As an aside, I wish clubs would be more clear when stating their waiver altitude. Some say ASL, some say AGL, most don't specify either way. This becomes more important west of the Mississippi!!!

I would think the areas east of the Mississippi would be more critical. With most waivers below 15000, it's a lot easier to get near that waiver then when you have waivers 30K or so.

I get your point though. Our waiver comes from the FAA as 16,000 ft above mean sea level (MSL). Our site is at 400 ft above sea level so if you stay 10% below the waiver, you're still good.