Topics

table of GPSL altitudes

Hank Riley
 

where you list the groups and their
balloons, what about adding another column and listing
the altitudes? I think I saw a
chart of altitudes early after the flights.
Don,

I think you're remembering my post to TVNSP list (and maybe
a few other lists). It didn't go here, so here's it is
from July 7 (a few extra words added here and there). Since
this was written, Paul has a peak altitude revised slightly
upward by a couple hundred feet from what is shown below.

Hank
--------------------------------------------



July 7
------

meters feet

Paul 26796 87900 (87913)
Mike 26671 87500 (87503)
Don 26052 85500 (85472)
Mark* 24987 82000 (81978)
Zack 22167 72700 (72726)

*reported in feet and converted to meters

-------------------------------------------------------

This is what I get from using the igated data of the highest
*reported* altitudes. I've shown the feet converted from meters
rounded to hundreds of feet to set an example of showing data
to a reasonable degree of precision but no more (the
down-to-the-foot figures are in parentheses for those who
insist, but it's not a good practice).

Paul and Mike are already within a remarkably close 400 feet
of each other, and Paul's igated figures suggest that his peak
was almost caught perfectly by the timing of the packet
transmissions. Mike's figures don't indicate a favorable timing
(although it can't be ruled out), so to my way of thinking Mike's
balloon in actuality may have edged out Paul's by as much as
several hundred feet.

I offer these comments just to illustrate there is a certain
approximation involved in pegging a balloon's height without
more frequent measurements of the balloon's altitude and with
the limitations of GPS vertical accuracy. With this in mind, I
think it's best to consider it a tie between the first two in
the list.

The important point is that balloon altitudes by consumer GPS with
coarse reporting (every 60 or 30 seconds) are really only accurate
to within a hundred feet of absolute vertical position at best,
and likely err by as much as 500 feet in the direction of
underestimating altitude (because of the too infrequent measurement
cycle).

Hank

Hank Riley
 

Paul 26796 87900 (87913)

Paul (revised) 88200 (88163)


Do I think this reporting precision issue is
worthwhile to discuss?

Yes.

Reporting to a reasonable precision and no more
shows that the investigator is informed and aware
of the shortcomings of his data collection methods.

If this kind of data were ever to make it to an
engineering or scientific publication, the altitude
figures stated down to the foot, at least without
some qualification, would go out the window. They
just wouldn't get by the editor.

I know it's natural to use all the digits if you
have them, but it's not good practice because
the implied precision is bogus.

Hank

Don Pfister <ka0jlf@...>
 

Yes, I meant to come back to this but have been sidetracked. One of the things I
have tried to do in the past was to capture the GPS data too. Mainly I was
interested in the Satelite data, number, signal strength, 2D/3D fix etc.

One of my main interests is that GPS info. With all the balloons, and the
inability to get my second beacon (GPS payload) running in time for the launch
(later I realized I hooked up the RD instead of the TD line) I didn't fly the
second beacon which would have sent the GPS data on a different band. Oh well
there will be next year for GPSL. And another HABITAT SkyLab flight probably
Aug. 3.

Sorry this was just a running off at the fingers (yet again, been a lot of that
from me lately).

Thanks,
Hank

n1ltv wrote:

Paul 26796 87900 (87913)

Paul (revised) 88200 (88163)

Do I think this reporting precision issue is
worthwhile to discuss?

Yes.

Reporting to a reasonable precision and no more
shows that the investigator is informed and aware
of the shortcomings of his data collection methods.

If this kind of data were ever to make it to an
engineering or scientific publication, the altitude
figures stated down to the foot, at least without
some qualification, would go out the window. They
just wouldn't get by the editor.

I know it's natural to use all the digits if you
have them, but it's not good practice because
the implied precision is bogus.

Hank


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Name=Don Pfister KA0JLF
HABITAT SkyLab soon to add SeaLab (underwater robotics)
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http://habitat.netlab.org
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http://www.findu.com/cgi-bin/find.cgi?KA0JLF-11 balloon

Hank Riley
 

Don,

While you're around, inquiring minds would like to know
the weight of your GPSL HABITAT payload.

Surely you must be able to give a pretty good estimate
or actually drop it on a scale and weigh it. :)

Hank

Don Pfister <ka0jlf@...>
 

Actually it is still in the car from the launch, then photo shoot. I'll go get
it and get this checked off my "To Do" list. ;-)
It even made the trip to NE and back. ;-)

Back in a few,
Don (slow)

n1ltv wrote:

Don,

While you're around, inquiring minds would like to know
the weight of your GPSL HABITAT payload.

Surely you must be able to give a pretty good estimate
or actually drop it on a scale and weigh it. :)

Hank