IGC files and wind updates in LX9000

[lonkelly]

1. Does anyone know how often LX9000 updates the wind, and if each time the wind is updated on the LX9000 display it will be written to the IGC file for the flight?

2. Does anyone have a reference to how SeeYou determines wind speed and direction and if they use wind speed and direction from IGC files where it is available?

BACKGROUND:

I've built a rough and ready IGC file parser in Perl to extract data from LX9000 IGC files to be used to overlay those data on GoPro video. I'm interested in data that are not available directly from the GoPro metadata, particularly True Airspeed (TAS) and Vario (VAT), which are available in the IGC file.

In doing this I noticed there are IGC "K-records" in the log files that periodically update the wind speed and direction. In my test IGC file, which covers under 7 minutes of flight, there are 3 K-records. When I step through the flight with SeeYou Cloud the web app updates the wind periodically, but not in alignment or agreement with the K-records. SeeYou updates wind more often, and is never the same direction or speed as shown in the K-records even for the same timestamp.

[the_gle...@msn.com]

Both Naviter and LX Nav are quite good at answering emails. Why don't you email them to ask.

On the LX9000, you can show both average wind and current wind - you need to ask the question for both!

[lonkelly]

Thank you. I did not know LXNAV would respond to technical questions from users. I've posed my questions through their web contact interface and will post any response I receive regarding the IGC files and wind calculations.

[lonkelly]

That was fast. LXNAV responded to my query within minutes. Their answers in italics.

1. When does LX9000 does the LX9000 update the calculated wind speed and direction for display and logging?

lx9xxx calculates two winds

Actual (realtime) wind and average wind

Actual is updated after each new wind calcultion. Average is taken over long time period of few minutes.

The update rate of real time wind depends on the wind method. 

Groundspeed method needs 2 two turns, position method 6 turns, iteration method is for straight flying needs few seconds.  The fastest is the compass method which relays to the gp frequency. In lx9xxx is 1/s. It could be increased up to 5 to 10Hz.

New HAwk is also very fast, calculates wind several times per second. Hawk is not yet available for lxxxx, but only for sxxx varios. 

2. Will the calculated wind be written as a K-record to the IGC file for the flight each time the wind is updated on the display?

in K record is written actual average wind

[the_gle...@msn.com]

Very impressively quick reply but slightly confusing. 

1. I don't have a compass unit (in the past they told me the wind calculation was quite good without it, and I agree. They did not particularly recommend the compass unit at that time). I can set wind calculation to speed difference, position drift, or combination and I have all ticked. It is a pity he uses different terminology in his reply about the frequency of calculation.

2. What is the actual average wind written in the K record? He has just told us the device calculates an actual wind and an average wind, so which one is it? If the IGC record you looked at had 3 updates in 7 minutes, I would guess the K record uses what he called average wind. Will you now write to Naviter to ask how SeeYou derives the wind?

Great news that we are going to benefit from very rapid wind calculation from HAwk in due course - which is apparently a software development using our existing hardware devices.

[lonkelly]

Since the K-record are only written every few minutes, I'd decided Uros meant the K-records were average wind.

I have written to Naviter about how SeeYou updates the wind and if/when they reply I'll post it to this conversation.

[lonkelly]

UPDATE: The K-records recording the wind direction and velocity appear, in the IGC files I've been working with, to be written every 181 seconds after the first one. I haven't seen a pattern as to when the first K-record is written to the IGC file.

[lonkelly]

UPDATE: Response from Naviter on how SeeYou calculates the wind:

Hi Lon,

SeeYou does its own Wind calculation which uses the data recorded in K-records, but also applies calculations it does in real time, even better, it uses sensors input "from the future" because it can.

To compute the wind, it uses algorithms that include Indicated airspeed in the calculation. Because it uses data from the future, these values will not be the same as the ones you saw in the glider.

Regards,

Andrej KolarEnabling pilot excellence