[aprssig] Balloon - lessons learned (AVMAP-GPS) - GreenLight Labs GPS?

Joe Dempster joe.dempster at gmail.com
Mon Apr 7 15:58:10 CDT 2014


Amir, are you telling us Bob got separated from the balloon search team,
was lost for some time, and thus the dog collar recommendation?

73 de Joe K2EVK


On Mon, Apr 7, 2014 at 3:57 PM, Amir Findling <sarlabs at gmail.com> wrote:

> Talking to the father of APRS, you may perhaps want to see me burned at
> the stake for heresy, but here is what I have to say:
>
> Maybe the Garmin Astro dog collar and base unit may work better just
> because they are made to show the actual dog position. Not APRS, nor ham
> frequencies... Might work though...
>
> --
>
> 73 de Amir K9CHP
> Member ARRL, VE (ARRL and W5YI), WAC, WAS, DXCC
> www.k9chp.net http://k9chp.blogspot.com
> Liverpool Amateur Repeater Club www.W2CM.org
> Eagle Valley Search Dogs www.evdogs.org
> On Apr 7, 2014 12:32 PM, "Robert Bruninga" <bruninga at usna.edu> wrote:
>
>> See web page for summary of the balloon mission:
>> http://aprs.org/balloons.html
>>
>>
>>
>> APRS Lessons Learned: -- What the  GPS map shows MAY NOT BE what your
>> radio knows.
>>
>>
>>
>> We were running a GreenLight Labs GPS on the D710:
>> http://www.greenlightlabs.com/gps-710/
>>
>>
>>
>> For the chase, we added an AVMAP GPS for the map display and plugged it
>> into the "pass-through" socket on the Green light labs GPS.  Everything
>> seemed to be working.
>>
>>
>>
>> 20/20 HINDSIGHT HINTS:  Occasionally we notice the D710 was not updating
>> and so we cycled power and continued.  Some times the AVMAP was not
>> updating.  Sometimes when the AVMAP was plugged into the Green Light Labs
>> GPS, then the D710 did not get GPS updates.  But generally, a power cycle
>> fixed it.  Did it maybe 3 times during the all day chase.
>>
>>
>>
>> PROBLEM:  What screwed us up was "assuming" that the balloon ICON SHOWING
>> on the AVMAP GPS was the same last-updated balloon data showing on the
>> Kenwood D710.  So we were visually driving and chasing the BALLOON ICON on
>> the AVMAP not realizing that it was the 2nd from last actual position
>> data heard.  But each time we LOOKED at  the data on the kenwwod we WERE
>> seeing the last known position (looking mostly to see the altitude).  But
>> you see, they were not the same.  Apparently the last two packets did not
>> make it to the AVMAP.  So we were searching based on the time and altitiude
>> on the radio and the visual map data on the AVMAP, not realizing they were
>> different.
>>
>>
>>
>> Finally when I happened to compare LAT/LONG numbers on the radio, to our
>> searching area, it was 7 miles to the east!
>>
>>
>>
>> And searching through the 150+ AVMAP APRS entries provided nothing to
>> correlate the two.  (it shows no lat/long and the altitude it shows is the
>> LAND elevation, not the balloon!)  And since I was completely trusting the
>> balloon ICON on the GPS map display, I never noticed that the distance and
>> bearing on the Radio was showing it 7 miles away.
>>
>>
>>
>> 20/20 Hindsight.  Always use the final data in the RADIO as the last
>> known information.  It has to be right.  There may have been a transmission
>> error between the radio and the GPS display.
>>
>>
>>
>> WB4APR, Bob
>>
>>
>>
>>
>>
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>>
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