SeeYou wind calculations

Hi Gary,

What GPS or flight computer is the PDA and SeeYou Mobile receiving data
from?

Paul Remde

"GARY BOGGS CFIG" wrote in message
...
Here in Hood River, Oregon, USA, we usually have lots of wind and
sometimes when I view the flights on SeeYou, it shows the wind very
accurately and sometimes it doesn't. It doesn't seem to matter if
there is a lot of circling on the flight or not. Sometimes when I
first look at the flight it doesn't show any wind and then when I view
the flight again, later there is wind shown. Has anybody else had
this problem? Does anybody have a suggestion for a fix?

Thanks

On Sep 27, 11:58*am, "Paul Remde" wrote:
Hi Gary,

What GPS or flight computer is the PDA and SeeYou Mobile receiving data
from?

Paul Remde

"GARY BOGGS CFIG" wrote in ...



Here in Hood River, Oregon, USA, we usually have lots of wind and
sometimes when I view the flights on SeeYou, it shows the wind very
accurately and sometimes it doesn't. *It doesn't seem to matter if
there is a lot of circling on the flight or not. *Sometimes when I
first look at the flight it doesn't show any wind and then when I view
the flight again, later there is wind shown. *Has anybody else had
this problem? *Does anybody have a suggestion for a fix?

Thanks

More like how is the .IGC file created? e.g. is it a file from a
Cambridge 302 or is it created by SeeYou Mobile. In the later case
there is TAS data in IGC file that is used by SeeYou to calculate wind
without circling. If you have plain non-TAS enhanced IGC data and
little circling then by definition SeeYou is going to have a tough
time guestimating the wind. Even if there is TAS data in the file and
sufficient heading change to calculate wind without circling it does
seem that SeeYou needs to be run forward in time to pick up that data.
If you carefully advance up to any point I expect SeeYou winds to be
consistent within reason. If not you should send a sample file to
Naviter and describe how to reproduce the problem.

Wind calculated in flight even by the same device as is creating the
IGC file may behave differently from what you see post flight. The in
flight calcs may use TAS data but that may not be available to SeeYou,
and if it is it may be at a much coarser sample rate.


Very coarse sample rates in the IGC file even when circling can also
be a problem. Even the dumbest PDA is reading GPS data many times per
second. If that is reduced to once every 10 or so seconds it can
change the wind calcs.

So what data exactly are you driving SeeYou with?
Darryl

On Sep 27, 4:38*pm, Darryl Ramm wrote:
On Sep 27, 11:58*am, "Paul Remde" wrote:





Hi Gary,

What GPS or flight computer is the PDA and SeeYou Mobile receiving data
from?

Paul Remde

"GARY BOGGS CFIG" wrote in ...

Here in Hood River, Oregon, USA, we usually have lots of wind and
sometimes when I view the flights on SeeYou, it shows the wind very
accurately and sometimes it doesn't. *It doesn't seem to matter if
there is a lot of circling on the flight or not. *Sometimes when I
first look at the flight it doesn't show any wind and then when I view
the flight again, later there is wind shown. *Has anybody else had
this problem? *Does anybody have a suggestion for a fix?

Thanks

More like how is the .IGC file created? e.g. is it a file from a
Cambridge 302 or is it created by SeeYou Mobile. In the later case
there is TAS data in IGC file that is used by SeeYou to calculate wind
without circling. If you have plain non-TAS enhanced IGC data and
little circling then by definition SeeYou is going to have a tough
time guestimating the wind. Even if there is TAS data in the file and
sufficient heading change to calculate wind without circling it does
seem that SeeYou needs to be run forward in time to pick up that data.
If you carefully advance up to any point I expect SeeYou winds to be
consistent within reason. If not you should send a sample file to
Naviter and describe how to reproduce the problem.

Wind calculated in flight even by the same device as is creating the
IGC file may behave differently from what you see post flight. The in
flight calcs may use TAS data but that may not be available to SeeYou,
and if it is it may be at a much coarser sample rate.

Very coarse sample rates in the IGC file even when circling can also
be a problem. Even the dumbest PDA is reading GPS data many times per
second. If that is reduced to once every 10 or so seconds it can
change the wind calcs.

So what data exactly are you driving SeeYou with?
Darryl

On Sep 27, 4:38*pm, Darryl Ramm wrote:
[snip]
Darryl

What I was trying to add to my own post was...

And to be clear in my example the IGC file created by SeeYou Mobile
will contain TAS data if fed by say a Cambridge 302 which outputs TAS
data in the NMEA stream. Obviously if you feed SeeYou Mobile from pure
GPS source you don't get this. Another example is say an SN10 which
although it uses TAS for internal wind calculations does not pass it
to an external PDA for capturing to the PDA generated (unofficial) IGC
file. (Why that is escapes me.) It might capture the TAS or wind data
in it's own (unofficial) IGC file, I'm note sure. The point is the
exact providence of your data has a huge effect on the wind
calculations. For these reasons I'll often capture an official IGC
file in my C302MG (needed for OLC with a motorglider) but use the
SeeYou Mobile generated IGC file at 1 sec sample rate for analysis
because it captures TAS info for better wind calculations by SeeYou.

Darryl

I am getting my .igc file from a Colibri, and my sample rate is every
two seconds. I also removed SeeYou and reloaded a fresh version but
still show no winds sometimes.

On Sep 28, 7:35*am, GARY BOGGS CFIG wrote:
I am getting my .igc file from a Colibri, and my sample rate is every
two seconds. *I also removed SeeYou and reloaded a fresh version but
still show no winds sometimes.

The Collibri IGC file contains no TAS data. If as you say you don't
circle much SeeYou has no data to us to calculate a wind. I'd say
likely working as designed. Play the trace forward through a thermal
for the most accurate then current wind.

Darryl

What is TAS data?

Mike Schumann

"Darryl Ramm" wrote in message
...
On Sep 28, 7:35 am, GARY BOGGS CFIG wrote:
I am getting my .igc file from a Colibri, and my sample rate is every
two seconds. I also removed SeeYou and reloaded a fresh version but
still show no winds sometimes.

The Collibri IGC file contains no TAS data. If as you say you don't
circle much SeeYou has no data to us to calculate a wind. I'd say
likely working as designed. Play the trace forward through a thermal
for the most accurate then current wind.

Darryl

TAS = True Air Speed

With TAS data and GPS derived ground speed SeeYou can calculate wind
using the effect of heading changes and not need to rely on thermal
circle drift.

The IGC file format is modular and somewhat extensible and pretty well
documented. You can see what additional data is being written to the
file by looking at the file header.

In the case of a SeeYou Mobile generated file fed by a device like a
Cambridge 302 that passes TAS data in the NMEA stream then SeeYou
Mobile will include some of that data in the IGC file and IGC file
header will have a J options record like

I043640TAS4145GSP4648TRT4953VAR

This describes the format of additional data stored in each B record
(the standard time/position/altitude record). e.g. here "3640TAS"
characters 36 to 40 in a B record encode the TAS. They are also
encoding the Ground Speed (GSP) and True Track (TRT) but these are all
derivable by SeeYou so I'm not sure what SeeYou uses and I'm too lazy
to do the experiment. A possible reason to want to use these files is
these may be better numbers than you can derive from the IGC file if
the sample times are really coarse.

Now it also turns out SeeYou Mobile will write what it thinks the
winds are in the IGC file. It does that in a optional K records
interspersed amongst the B records. I think I have done the experiment
of deliberately erasing this data and I think I recall SeeYou seems to
want to recalculate the its own wind from the TAS not pull them out of
the J record, but I could be wrong on that.

The header will have an optional record J definition that defines the
I record. Something like...

J020810WDI1115WVE

That says there are 02 data fields in a K record.

The first fields is WDI (Wind Direction) in characters 08 to 10
The second field is WVE (Wind Velocity in km/h) in characers 11 to 15
(I guess Naviter did not get the memo about using WSP :-))
The preceding characters are a standard time stamp

Then amongst the B records you'll see things like

K20253329400074

Anyhow bottom line is IGC files can be quite different and if you want
good non-circling wind you *won't* get it from an IGC file from a
simple GPS output converted to IGC or from a Colibri like flight
recorder.

You can open any IGC file with a text editor and look for the
existence of I and J records to show if TAS or wind data is written to
the file or not. Given modern compute power it really seems a waste
not to be logging this stuff in detail at 1 Hz rates, makes for great
play back in SeeYou.

Darryl


On Sep 28, 7:32*pm, "Mike Schumann" mike-nos...@traditions-
nospam.com wrote:
What is TAS data?

Mike Schumann
[snip]