Wed 7/15 fantastic day, but SPOT??

[Hellman]

I soared from the Minden area down to abeam Independence then back to
Mono Lake before needing my engine to get home to the Bay Area. (I
also used the engine to get me to Minden.) As long as I stayed with
the clouds, lift was fantastic east of the Sierras. I saw 13 kts on my
averager several times, and 10 knots while dolphin flying. South of
Mono Lake, there were clouds that could take you to the Whites or the
Sierras and, since I'm a sucker for soaring the Sierras, I took that
fork in the clouds. Made it to abeam Independence before turning
around. Lift on the Sierras was spottier -- as usual, but still very
good.

When I got home and checked my SPOT messenger track was missing an
hour and twenty minutes -- a new record. The last message before the
dropout was at 12:10 PM PDT and the next one was around 1:30 PM. Did
anyone else with a SPOT have a similar problem today? If anyone wants
to compare data, my shared page is

http://share.findmespot.com/shared/faces/viewspots.jsp?glId=0BQITGzXK57fBVRGBJqB6QTLgQBTp7N ax

but, as usual, it will disappear in a few days or a week.

Thanks for any help on this question.

Martin

[Tuno]

Martin,

I've had several flights with that long of a gap in the tracking
messages. No one has come up with a good explanation.

Is your flight on OLC ... ? Thirteen knots, you gotta share that!

ted/2NO

[Steve Koerner]

Martin:

I did a serious investigation on the problem involving some
experiments and analysis and I made a presentation to my local club.
My presentation is available for download from my Wing Rigger website:
www.wingrigger.com. (click Extra Soaring Content in lower right
corner).

Here is the bottom line: the radio link between Spot and the Global
Star network is a bit fussy. There are some 40 Global Star satellites
in low earth orbit. Statistically 2 or 3 satellites are likely to be
in view but sometimes just one. When you consider the geometry of
the low earth orbit and the statistical distribution of the satellites
it will almost always be the case that the satellites are very near to
the horizon. So what matters is that Spot has a line of site view to
the horizon. Since you don’t know exactly where on the horizon the
Global Star will be, the only sure thing is to have a clear view of
the entire horizon. This is often rather difficult. My experiments
proved that when you do have a 360 degree view of the horizon Spot
works perfectly. So part of the answer relates to the mounting
location in your glider. What I found works best is a location
behind my headrest high against the underside of the canopy. I have a
picture of this mounting in the mentioned presentation.

There is more to the story. Even with optimal mounting you will miss
some Spot transmissions because gliders spend a portion of their time
in banked turns. When the glider is banked, a certain percentage of
the horizon becomes blocked by the glider’s wings, fuselage etc. If
there aren’t any satellites in the unblocked portion of the horizon,
your message won’t get out. I studied this effect by carefully time
correlating the exact times at which Spot succeeded or failed in its
transmissions to the time stamped record created by an IGC file that I
examined in See You. I did this for two long flights. With my
“optimal mounting” I miss about 20% of transmissions while banked and
I miss only 2% when in substantially level flight. So my Spot
tracking performance is pretty good, but certainly not perfect.

One other consideration relates to the performance of the patch
antenna that is used in the Spot device. The antenna preferentially
transmits to one hemisphere. So the unit works best when the unit is
mounted flat – label side up. Any other mounting angle reduces your
chance of linking to a satellite on the horizon. I’m sure this also
comes into play when the glider is in a banked turn.

Steve Koerner (GW)

[Steve Koerner]

PS:

Martin:

Here is a link to my Spot log for a long flight I made in AZ/UT the
day before yours: www.tinyurl.com/4fuc2h
I missed only one transmission in eight hours on that flight. That's
better than I would have expected. Since it was a high altitude
flight, I'm thinking that might have helped the odds of seeing more
horizon distance.

PPS:

Tuno: Were you sleeping during my lecture?

Steve

[Hellman]

On Jul 16, 6:04*am, Tuno > wrote:
> Is your flight on OLC ... ? Thirteen knots, you gotta share that!

Alas, I've been unable to read the files from my Colibri data logger
since I upgraded my PC's OS -- the Colibri uses a serial port and
either my serial-USB adapter doesn't work since that upgrade or the
Colibri itself is broken. I've seen 11 kts before on the averager, but
I am pretty sure 13 is a new record for mine, especially in 3 or 4
thermals in the same flight. Once I took the fork to the Sierras, the
lift was nowhere as good -- though that was partly expected. I was
willing to sacrifice thermal strength (and maybe even having to turn
on the engine) for the fantastic views the Sierras offer compared to
the more barren ranges to the east. Meadows, lakes, glacial remnants
make for great sightseeing, but do cut into thermals. Coming home to
the Bay Area was a bit problematic in that the clouds made an arc far
to the east before I could cross the Sierras, so I had to turn on the
engine for about 10 minutes near Mammoth Lakes to gain enough altitude
to safely cross as a glider at Yosemite. But I'd kinda expected that
since the BLIPMAP showed that would be the case at 5 PM local time.
Even so, I had a 6.6 hour flight with only 1.0 engine time.

Sorry not to be able to post the track, but an earlier one-day trip is
described (including a SeeYou map, showing engine use) at
http://tinyurl.com/5ahbcm

Martin

PS The ship is for sale. I'll miss it, but a project is taking too
much time and passion that used to go in here. If interested,
http://tinyurl.com/56qseu has a description of that project -- and
even connects it to soaring.

[Hellman]

On Jul 16, 7:48*am, Steve Koerner > wrote:
> I did a serious investigation on the problem involving some
> experiments and analysis and I made a presentation to my local club.
> My presentation is available for download from my Wing Rigger website:www..wingrigger.com. *(click Extra Soaring Content in lower right
> corner).

Steve,

Thanks for that detailed analysis of SPOT behavior. While it helps in
understanding SPOT generally, my question -- and big concern -- is why
that flight was different from all other flights. I don't believe I've
never had more than a 30 minute gap (2 missed transmissions) before,
yet this time the gap was 90 minutes (8 missed transmissions). I was
asking if anyone else had a track from that specific day and time (JUL
15, 1900-2020 Z) and general location (roughly from Oakland, CA to
Lake Tahoe). If so, I wanted to know if they had coverage or also had
around a 90 minute hole in their data.

Martin

[Darryl Ramm]

On Jul 17, 9:08*pm, Hellman > wrote:
> On Jul 16, 7:48*am, Steve Koerner > wrote:
>
> > I did a serious investigation on the problem involving some
> > experiments and analysis and I made a presentation to my local club.
> > My presentation is available for download from my Wing Rigger website:www.wingrigger.com. *(click Extra Soaring Content in lower right
> > corner).
>
> Steve,
>
> Thanks for that detailed analysis of SPOT behavior. While it helps in
> understanding SPOT generally, my question -- and big concern -- is why
> that flight was different from all other flights. I don't believe I've
> never had more than a 30 minute gap (2 missed transmissions) before,
> yet this time the gap was 90 minutes (8 missed transmissions). I was
> asking if anyone else had a track from that specific day and time (JUL
> 15, 1900-2020 Z) and general location (roughly from Oakland, CA to
> Lake Tahoe). If so, I wanted to know if they had coverage or also had
> around a 90 minute hole in their data.
>
> Martin

Martin

You want to end the guessing game and tell us where your SPOT
messenger is mounted? On your harness? On your shoulder? Obstructed
by your head? What is the effective field of view of the antenna?

You were tracking roughly the same heading for all that time. And
that heading (very) roughly lines up with one of the inclined planes
of the GlobalStar constellation.

The GlobalStar satelites orbit in a interweaved pattern with two
inclined planes at +/- 80 degrees or so (you can see a simulation here
http://www.youtube.com/watch?v=G8VPEueequM or you can actually play
with the SaVi software shown in the video, see http://savi.sourceforge.net)..
It is quite possible that things happen like the satelites flying from
the south west to north east are obscured over your left shoudler if
say your SPOT messenger was to the right side of your head and all
those passes could be obscured and maye the next parallel path to the
east is too far away. That leaves the satellites tracking north-west
to south-east and just maybe again if your head partially obscured
those then the satellite does not see the spot until it is further
overhead and out of the optimal bent-pipe geometry to reach the
Alberta, Canada ground station. So maybe in the whole time you just
get maybe one shot when the SPOT fires off its track message where it
manages to see a satellite to get it a bent path to the Texas ground
station. Maybe you just managed to get things timed so bad that you
never happened to have a satellite with bent-pipe view to any ground
station when your SPOT happened to fire the TRACK message.

This is all very uninteresting if the SPOT messenger is mounted say on
your parachute harness and inclined or significantly obscured. Tell me
it is out flat in the open and I'll actually care.

Darryl

[Ramy]

On Jul 17, 10:34*pm, Darryl Ramm > wrote:
> On Jul 17, 9:08*pm, Hellman > wrote:
>
>
>
>
>
> > On Jul 16, 7:48*am, Steve Koerner > wrote:
>
> > > I did a serious investigation on the problem involving some
> > > experiments and analysis and I made a presentation to my local club.
> > > My presentation is available for download from my Wing Rigger website:www.wingrigger.com. *(click Extra Soaring Content in lower right
> > > corner).
>
> > Steve,
>
> > Thanks for that detailed analysis of SPOT behavior. While it helps in
> > understanding SPOT generally, my question -- and big concern -- is why
> > that flight was different from all other flights. I don't believe I've
> > never had more than a 30 minute gap (2 missed transmissions) before,
> > yet this time the gap was 90 minutes (8 missed transmissions). I was
> > asking if anyone else had a track from that specific day and time (JUL
> > 15, 1900-2020 Z) and general location (roughly from Oakland, CA to
> > Lake Tahoe). If so, I wanted to know if they had coverage or also had
> > around a 90 minute hole in their data.
>
> > Martin
>
> Martin
>
> You want to end the guessing game and tell us where your SPOT
> messenger is mounted? *On your harness? On your shoulder? Obstructed
> by your head? What is the effective field of view of the antenna?
>
> You were tracking roughly the same heading for all that time. *And
> that heading (very) roughly lines up with one of the inclined planes
> of the GlobalStar constellation.
>
> The GlobalStar satelites orbit in a interweaved pattern with two
> inclined planes at +/- 80 degrees or so (you can see a simulation herehttp://www.youtube.com/watch?v=G8VPEueequMor you can actually play
> with the SaVi software shown in the video, seehttp://savi.sourceforge.net).
> It is quite possible that things happen like the satelites flying from
> the south west to north east are obscured over your left shoudler if
> say your SPOT messenger was to the right side of your head and all
> those passes could be obscured and maye the next parallel path to the
> east is too far away. That leaves the satellites tracking north-west
> to south-east and just maybe again if your head partially obscured
> those then the satellite does not see the spot until it is further
> overhead and out of the optimal bent-pipe geometry to reach the
> Alberta, Canada ground station. So maybe in the whole time you just
> get maybe one shot when the SPOT fires off its track message where it
> manages to see a satellite to get it a bent path to the Texas ground
> station. Maybe you just managed to get things timed so bad that you
> never happened to have a satellite with bent-pipe view to any ground
> station when your SPOT happened to fire the TRACK message.
>
> This is all very uninteresting if the SPOT messenger is mounted say on
> your parachute harness and inclined or significantly obscured. Tell me
> it is out flat in the open and I'll actually care.
>
> Darryl- Hide quoted text -
>
> - Show quoted text -

I don't think I agree with the notion that mounting a spot on the
parachute harness near the shoulder is bad idea. Mine is on the
parachute harness and I get around 10% drops, as good as anyone else
who mounts their Spot perfectly horizontally. I just checked my spot
messages from today: 5 missing messages in 7.5 hours fligh = 10%
Since installing on the parachute harness is the easiest, and provide
easy access during flight, and will stay with you in case of bailout,
I wouldn't recommend against it.

Ramy

[Darryl Ramm]

On Jul 17, 11:50*pm, Ramy > wrote:
> On Jul 17, 10:34*pm, Darryl Ramm > wrote:
>
>
>
> > On Jul 17, 9:08*pm, Hellman > wrote:
>
> > > On Jul 16, 7:48*am, Steve Koerner > wrote:
>
> > > > I did a serious investigation on the problem involving some
> > > > experiments and analysis and I made a presentation to my local club..
> > > > My presentation is available for download from my Wing Rigger website:www.wingrigger.com. *(click Extra Soaring Content in lower right
> > > > corner).
>
> > > Steve,
>
> > > Thanks for that detailed analysis of SPOT behavior. While it helps in
> > > understanding SPOT generally, my question -- and big concern -- is why
> > > that flight was different from all other flights. I don't believe I've
> > > never had more than a 30 minute gap (2 missed transmissions) before,
> > > yet this time the gap was 90 minutes (8 missed transmissions). I was
> > > asking if anyone else had a track from that specific day and time (JUL
> > > 15, 1900-2020 Z) and general location (roughly from Oakland, CA to
> > > Lake Tahoe). If so, I wanted to know if they had coverage or also had
> > > around a 90 minute hole in their data.
>
> > > Martin
>
> > Martin
>
> > You want to end the guessing game and tell us where your SPOT
> > messenger is mounted? *On your harness? On your shoulder? Obstructed
> > by your head? What is the effective field of view of the antenna?
>
> > You were tracking roughly the same heading for all that time. *And
> > that heading (very) roughly lines up with one of the inclined planes
> > of the GlobalStar constellation.
>
> > The GlobalStar satelites orbit in a interweaved pattern with two
> > inclined planes at +/- 80 degrees or so (you can see a simulation herehttp://www.youtube.com/watch?v=G8VPEueequMoryou can actually play
> > with the SaVi software shown in the video, seehttp://savi.sourceforge.net).
> > It is quite possible that things happen like the satelites flying from
> > the south west to north east are obscured over your left shoudler if
> > say your SPOT messenger was to the right side of your head and all
> > those passes could be obscured and maye the next parallel path to the
> > east is too far away. That leaves the satellites tracking north-west
> > to south-east and just maybe again if your head partially obscured
> > those then the satellite does not see the spot until it is further
> > overhead and out of the optimal bent-pipe geometry to reach the
> > Alberta, Canada ground station. So maybe in the whole time you just
> > get maybe one shot when the SPOT fires off its track message where it
> > manages to see a satellite to get it a bent path to the Texas ground
> > station. Maybe you just managed to get things timed so bad that you
> > never happened to have a satellite with bent-pipe view to any ground
> > station when your SPOT happened to fire the TRACK message.
>
> > This is all very uninteresting if the SPOT messenger is mounted say on
> > your parachute harness and inclined or significantly obscured. Tell me
> > it is out flat in the open and I'll actually care.
>
> > Darryl- Hide quoted text -
>
> > - Show quoted text -
>
> I don't think I agree with the notion that mounting a spot on the
> parachute harness near the shoulder is bad idea. Mine is on the
> parachute harness and I get around 10% drops, as good as anyone else
> who mounts their Spot perfectly horizontally. I just checked my spot
> messages from today: 5 missing messages in 7.5 hours fligh = 10%
> Since installing on the parachute harness is the easiest, and provide
> easy access during flight, and will stay with you in case of bailout,
> I wouldn't recommend against it.
>
> Ramy

But just don't do that and complain about gaps in your SPOT data. So
folks complaining about SPOT problems lets start with where is the
SPOT unit mounted and how much sky can it see? And Ramy you have been
on here complaining about gaps in your SPOT track in the past. I get
less than 10% drops. The next person with slightly more obscuration
who's flight happens to track the satellites in just the wrong way may
get a lot more. If you don't give them a really good sky view you are
going to see gaps in the data. That is your trade-off, just don't be
surprised when it happens.

Maybe Martin's is mounted with a clear sky view.. who knows.

Darryl

[WaltWX]

Some comments on the performance of my SPOT during flights this year,
2009, before and after I relocated it from my parachute harness to a
flat position on the forward instrument panel cover. BOTTOM LINE...
place you SPOT in the glider in a horizontal position with an
unobstructed view from horizon to horizon.

I fly "WX" a Discus 2A. Last year and for the first six flights this
year my SPOT was located on my parachute shoulder harness and is
aligned about 45deg to horizontal. Starting with my 06/28/09 flight at
Parowan it was re-located to a horizontal position on the forward
instrument cover.

Here are some statistics on the number of drop-outs during tracking
mode (updates every 10minutes). The percent number is the number of
dropout per flight. The number of track is the total (i.e. includes
the tracks that were lost). Results showed a dramatic improvement:

Date No Tracks No Drop Outs Per Cent Drops

03/15/09 12 2 17%
05/05/09 36 16 44%
06/19/09 22 8 36%
06/22/09 15 3 20%
06/23/09 28 5 18%
06/24/09 19 7 36%

Total dropouts cumulative: 31%

After re-locating to flat orientation forward instrument panel cover

06/28/09 29 0 0%
06/30/09 30 0 0%
07/01/09 25 1 4%
07/03/09 31 1 4%
07/04/09 23 0 0%
07/14/09 37 3 8%

Total dropouts cumulative: 4%

Walt Rogers, WX

[Hellman]

On Jul 17, 10:34 pm, Darryl Ramm > wrote:
> You want to end the guessing game and tell us where your SPOT
> messenger is mounted? On your harness? On your shoulder? Obstructed
> by your head? What is the effective field of view of the antenna?
>
> You were tracking roughly the same heading for all that time. And
> that heading (very) roughly lines up with one of the inclined planes
> of the GlobalStar constellation.

Darryl,

My SPOT is mounted in an indent in my glare shield (which is radio
transparent) well forward, and is oriented horizontally. While it
loses a little bit of the horizon to the rear (carbon fiber turtle
deck), it's a pretty good location. More to the point, as to why I
asked if anyone else had problems on that day in that locality, I've
NEVER seen more than two (maybe three, my memory isn't as good as it
used to be) dropped messages and here it was eight. Assuming rough
independence between dropped messages, that kind of jump (from 2 or 3
to 8 occurrences) would be highly unlikely. That's why I wondered what
happened.

While your theory about my track being fairly constant and possibly
aligned badly with the satellites is a possibility, I've never had
that problem before and whenever I fly from Hayward to the Tahoe area
I fly a roughly similar track. There's almost never any lift on that
part of the flight, so I fly pretty much direct.

Since no one else mentioned a big gap that day, I'm assuming the
problem was unique to me. One thing that came out of this: I've told
my wife not to look at the SPOT track to watch my progress. A huge gap
like that looks too much like a ship gone down.

Martin

[Darryl Ramm]

On Jul 20, 7:27*pm, Hellman > wrote:
> On Jul 17, 10:34 pm, Darryl Ramm > wrote:
>
> > You want to end the guessing game and tell us where your SPOT
> > messenger is mounted? *On your harness? On your shoulder? Obstructed
> > by your head? What is the effective field of view of the antenna?
>
> > You were tracking roughly the same heading for all that time. *And
> > that heading (very) roughly lines up with one of the inclined planes
> > of the GlobalStar constellation.
>
> Darryl,
>
> My SPOT is mounted in an indent in my glare shield (which is radio
> transparent) well forward, and is oriented horizontally. While it
> loses a little bit of the horizon to the rear (carbon fiber turtle
> deck), it's a pretty good location. More to the point, as to why I
> asked if anyone else had problems on that day in that locality, I've
> NEVER seen more than two (maybe three, my memory isn't as good as it
> used to be) dropped messages and here it was eight. Assuming rough
> independence between dropped messages, that kind of jump (from 2 or 3
> to 8 occurrences) would be highly unlikely. That's why I wondered what
> happened.
>
> While your theory about my track being fairly constant and possibly
> aligned badly with the satellites is a possibility, I've never had
> that problem before and whenever I fly from Hayward to the Tahoe area
> I fly a roughly similar track. There's almost never any lift on that
> part of the flight, so I fly pretty much direct.
>
> Since no one else mentioned a big gap that day, I'm assuming the
> problem was unique to me. One thing that came out of this: I've told
> my wife not to look at the SPOT track to watch my progress. A huge gap
> like that looks too much like a ship gone down.
>
> Martin

Martin

My comment has no meaning if your SPOT messenger has a good all round
view. I was assuming it maybe did not and was just noticing the rough
alignment with the satellite tracks. I am as stumped as you.

Throwing out a random comment. If there is any reason the GPS does not
have a fix the SPOT messenger just won't send a TRACK message. (It
will send a HELP or 911 message with no fix, at least to let people
know you are in trouble). Now of course there is no reason to expect
the device not to have a GPS fix (and if you happened to look at it
while it was you would see the LEDs alternately blinking). Oh here is
one - any chance you were running the engine all that time and have
some really bad electrical interference? (yes I now an awful long
shot, especially given the SPOT is not electrically connected).


Darryl

[Eric Greenwell]

Hellman wrote:
> While your theory about my track being fairly constant and possibly
> aligned badly with the satellites is a possibility, I've never had
> that problem before and whenever I fly from Hayward to the Tahoe area
> I fly a roughly similar track. There's almost never any lift on that
> part of the flight, so I fly pretty much direct.
>
> Since no one else mentioned a big gap that day, I'm assuming the
> problem was unique to me.

Have you contacted the SPOT people about this? If there was a system
problem, they should know about it and be able to tell you if it caused
your track point losses. Possibly, some SPOTs might have problems, and
maybe they can determine if yours is one of them from what you report.
In about 75 flights with my SPOT, neither I nor my wife have noticed
more than two consecutive missing points.

> One thing that came out of this: I've told
> my wife not to look at the SPOT track to watch my progress. A huge gap
> like that looks too much like a ship gone down.

This is an interesting point. My wife likes the track reports so much, I
don't want to tell her that, but maybe she and I should decide
explicitly how many missed points are needed before starting to worry,
or initiating a search.

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly

* "Transponders in Sailplanes" http://tinyurl.com/y739x4
* Sections on Mode S, TPAS, ADS-B, Flarm, more

* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

[Ramy]

On Jul 20, 9:54*pm, Eric Greenwell > wrote:
> Hellman wrote:
>
> * > While your theory about my track being fairly constant and possibly
>
> > aligned badly with the satellites is a possibility, I've never had
> > that problem before and whenever I fly from Hayward to the Tahoe area
> > I fly a roughly similar track. There's almost never any lift on that
> > part of the flight, so I fly pretty much direct.
>
> > Since no one else mentioned a big gap that day, I'm assuming the
> > problem was unique to me.
>
> Have you contacted the SPOT people about this? If there was a system
> problem, they should know about it and be able to tell you if it caused
> your track point losses. Possibly, some SPOTs might have problems, and
> maybe they can determine if yours is one of them from what you report.
> In about 75 flights with my SPOT, neither I nor my wife have noticed
> more than two consecutive missing points.
>
> > One thing that came out of this: I've told
> > my wife not to look at the SPOT track to watch my progress. A huge gap
> > like that looks too much like a ship gone down.
>
> This is an interesting point. My wife likes the track reports so much, I
> don't want to tell her that, but maybe she and I should decide
> explicitly how many missed points are needed before starting to worry,
> or initiating a search.
>
> --
> Eric Greenwell - Washington State, USA
> * Change "netto" to "net" to email me directly
>
> * "Transponders in Sailplanes"http://tinyurl.com/y739x4
> * * * Sections on Mode S, TPAS, ADS-B, Flarm, more
>
> * "A Guide to Self-launching Sailplane Operation" atwww.motorglider.org

In addition to the occasionly missing messages, there are occasionly
delays of an hour or more till the message shows up on the shared
page. Sometime 2 or 3 messages will show up at once. This is likely a
delay in the Spot backend system, not the communication system. As a
result, I would say that delays of up to 2 hours should not be an
immediate concern.

Ramy

[Ramy]

On Jul 17, 11:50*pm, Ramy > wrote:
> On Jul 17, 10:34*pm, Darryl Ramm > wrote:
>
>
>
>
>
> > On Jul 17, 9:08*pm, Hellman > wrote:
>
> > > On Jul 16, 7:48*am, Steve Koerner > wrote:
>
> > > > I did a serious investigation on the problem involving some
> > > > experiments and analysis and I made a presentation to my local club..
> > > > My presentation is available for download from my Wing Rigger website:www.wingrigger.com. *(click Extra Soaring Content in lower right
> > > > corner).
>
> > > Steve,
>
> > > Thanks for that detailed analysis ofSPOTbehavior. While it helps in
> > > understandingSPOTgenerally, my question -- and big concern -- is why
> > > that flight was different from all other flights. I don't believe I've
> > > never had more than a 30 minute gap (2 missed transmissions) before,
> > > yet this time the gap was 90 minutes (8 missed transmissions). I was
> > > asking if anyone else had a track from that specific day and time (JUL
> > > 15, 1900-2020 Z) and general location (roughly from Oakland, CA to
> > > Lake Tahoe). If so, I wanted to know if they had coverage or also had
> > > around a 90 minute hole in their data.
>
> > > Martin
>
> > Martin
>
> > You want to end the guessing game and tell us where yourSPOT
> > messenger is mounted? *On your harness? On your shoulder? Obstructed
> > by your head? What is the effective field of view of the antenna?
>
> > You were tracking roughly the same heading for all that time. *And
> > that heading (very) roughly lines up with one of the inclined planes
> > of the GlobalStar constellation.
>
> > The GlobalStar satelites orbit in a interweaved pattern with two
> > inclined planes at +/- 80 degrees or so (you can see a simulation herehttp://www.youtube.com/watch?v=G8VPEueequMoryou can actually play
> > with the SaVi software shown in the video, seehttp://savi.sourceforge.net).
> > It is quite possible that things happen like the satelites flying from
> > the south west to north east are obscured over your left shoudler if
> > say yourSPOTmessenger was to the right side of your head and all
> > those passes could be obscured and maye the next parallel path to the
> > east is too far away. That leaves the satellites tracking north-west
> > to south-east and just maybe again if your head partially obscured
> > those then the satellite does not see thespotuntil it is further
> > overhead and out of the optimal bent-pipe geometry to reach the
> > Alberta, Canada ground station. So maybe in the whole time you just
> > get maybe one shot when theSPOTfires off its track message where it
> > manages to see a satellite to get it a bent path to the Texas ground
> > station. Maybe you just managed to get things timed so bad that you
> > never happened to have a satellite with bent-pipe view to any ground
> > station when yourSPOThappened to fire the TRACK message.
>
> > This is all very uninteresting if theSPOTmessenger is mounted say on
> > your parachute harness and inclined or significantly obscured. Tell me
> > it is out flat in the open and I'll actually care.
>
> > Darryl- Hide quoted text -
>
> > - Show quoted text -
>
> I don't think I agree with the notion that mounting aspoton the
> parachute harness near the shoulder is bad idea. Mine is on the
> parachute harness and I get around 10% drops, as good as anyone else
> who mounts theirSpotperfectly horizontally. I just checked myspot
> messages from today: 5 missing messages in 7.5 hours fligh = 10%
> Since installing on the parachute harness is the easiest, and provide
> easy access during flight, and will stay with you in case of bailout,
> I wouldn't recommend against it.
>
> Ramy- Hide quoted text -
>
> - Show quoted text -

Couple of new feedbacks:

1 - Yesterday (8/9) I had 1 hour gap in messages along the Sierras
between Mammoth and Whitney. This was the longest gap I noticed so
far, long enough to get my wife concerned. As in Martin's case, there
was nothing special about this part of the flight then the rest. I
actually had more cloud coverage in other part of the flights then at
this section, so this rules out the clouds. My Spot is attached to my
parachute at 45 degrees. This is just FYI, not to restart the debate
re spot instalation...
2 - The Spot should not be attached to the parachute in the shoulder
area in a way that it may interfer with deployment. See important
notice from Allen Silver at
http://www.silverparachutes.com/files/Important_Notice_2009-07.pdf

Ramy

[Ramy]

On Aug 10, 1:56*pm, Ramy > wrote:
> On Jul 17, 11:50*pm, Ramy > wrote:
>
>
>
>
>
> > On Jul 17, 10:34*pm, Darryl Ramm > wrote:
>
> > > On Jul 17, 9:08*pm, Hellman > wrote:
>
> > > > On Jul 16, 7:48*am, Steve Koerner > wrote:
>
> > > > > I did a serious investigation on the problem involving some
> > > > > experiments and analysis and I made a presentation to my local club.
> > > > > My presentation is available for download from my Wing Rigger website:www.wingrigger.com. *(click Extra Soaring Content in lower right
> > > > > corner).
>
> > > > Steve,
>
> > > > Thanks for that detailed analysis ofSPOTbehavior. While it helps in
> > > > understandingSPOTgenerally, my question -- and big concern -- is why
> > > > that flight was different from all other flights. I don't believe I've
> > > > never had more than a 30 minute gap (2 missed transmissions) before,
> > > > yet this time the gap was 90 minutes (8 missed transmissions). I was
> > > > asking if anyone else had a track from that specific day and time (JUL
> > > > 15, 1900-2020 Z) and general location (roughly from Oakland, CA to
> > > > Lake Tahoe). If so, I wanted to know if they had coverage or also had
> > > > around a 90 minute hole in their data.
>
> > > > Martin
>
> > > Martin
>
> > > You want to end the guessing game and tell us where yourSPOT
> > > messenger is mounted? *On your harness? On your shoulder? Obstructed
> > > by your head? What is the effective field of view of the antenna?
>
> > > You were tracking roughly the same heading for all that time. *And
> > > that heading (very) roughly lines up with one of the inclined planes
> > > of the GlobalStar constellation.
>
> > > The GlobalStar satelites orbit in a interweaved pattern with two
> > > inclined planes at +/- 80 degrees or so (you can see a simulation herehttp://www.youtube.com/watch?v=G8VPEueequMoryoucan actually play
> > > with the SaVi software shown in the video, seehttp://savi.sourceforge..net).
> > > It is quite possible that things happen like the satelites flying from
> > > the south west to north east are obscured over your left shoudler if
> > > say yourSPOTmessenger was to the right side of your head and all
> > > those passes could be obscured and maye the next parallel path to the
> > > east is too far away. That leaves the satellites tracking north-west
> > > to south-east and just maybe again if your head partially obscured
> > > those then the satellite does not see thespotuntil it is further
> > > overhead and out of the optimal bent-pipe geometry to reach the
> > > Alberta, Canada ground station. So maybe in the whole time you just
> > > get maybe one shot when theSPOTfires off its track message where it
> > > manages to see a satellite to get it a bent path to the Texas ground
> > > station. Maybe you just managed to get things timed so bad that you
> > > never happened to have a satellite with bent-pipe view to any ground
> > > station when yourSPOThappened to fire the TRACK message.
>
> > > This is all very uninteresting if theSPOTmessenger is mounted say on
> > > your parachute harness and inclined or significantly obscured. Tell me
> > > it is out flat in the open and I'll actually care.
>
> > > Darryl- Hide quoted text -
>
> > > - Show quoted text -
>
> > I don't think I agree with the notion that mounting aspoton the
> > parachute harness near the shoulder is bad idea. Mine is on the
> > parachute harness and I get around 10% drops, as good as anyone else
> > who mounts theirSpotperfectly horizontally. I just checked myspot
> > messages from today: 5 missing messages in 7.5 hours fligh = 10%
> > Since installing on the parachute harness is the easiest, and provide
> > easy access during flight, and will stay with you in case of bailout,
> > I wouldn't recommend against it.
>
> > Ramy- Hide quoted text -
>
> > - Show quoted text -
>
> Couple of new feedbacks:
>
> 1 - Yesterday (8/9) I had 1 hour gap in messages along the Sierras
> between Mammoth and Whitney. This was the longest gap I noticed so
> far, long enough to get my wife concerned. As in Martin's case, there
> was nothing special about this part of the flight then the rest. I
> actually had more cloud coverage in other part of the flights then at
> this section, so this rules out the clouds. My Spot is attached to my
> parachute at 45 degrees. This is just FYI, not to restart the debate
> re spot instalation...
> 2 - The Spot should not be attached to the parachute in the shoulder
> area in a way that it may interfer with deployment. See important
> notice from Allen Silver athttp://www.silverparachutes.com/files/Important_Notice_2009-07.pdf
>
> Ramy- Hide quoted text -
>
> - Show quoted text -

Just noticed another gap in the same flight, even longer (80 minutes).
Both gaps are in the same general area around Bishop, one on the
Sierra the other on the Whites.

Ramy