[Gpsbabel-misc] IGC to KML: #track or #line

[Valerio M. <ef...@io...>]

hi,
I had to convert a FAI .IGC file taken with the Flarm anticollision.
The attached example small track time is about 30', and source file is about 80 kB.
Compressed with 7zip 16.x

I use GPSBabel Version 1.5.3 with this output options:

gpsbabel.exe -i igc -f 2016-10-29_6ATXETK1.IGC -o kml,floating=1,extrude=1,track=1,trackdirection=1,units=m -F 2016-10-29_6ATXETK1_1.5.3.kml

to keep the altitude absolute, draw an extrude down to terrain, and show direction on path.

The conversion work well, but the resulting file has some trouble:

1) the resulting KML is as expected and XML, with an open tag and close tag for each Placemark.
This generate a very big file, it this example is 3.8 MB.

2) 
there are many #track-N (with N up to 12) composed of many placemark named PRESALTTRK-NNN (up to 1819) with barometric altitude
there are many #track-N (with N up to 12) composed of many placemark named GNSSALTTRK-NNN (up to 1819) with GPS altitude
The two paths are overlapping and redundant, often is preferable choose only one, say filter one of the two.

Using and online service like:
http://cunimb.net/igc2kml.php
I got the "2016-10-29_6ATXETK1_online.kml" version, that has:
1) Waypoint saved as many "#line" of 500 coordinates, so no open/close tag in between.
2) only GPS altitude (or barometric altitude) is kept.
This save lot of space and resulting file is 42 KB.

Removing some of gpsbabel conversion output options I can reduce a little the output, but result is anyway an hundred size the online conversion.
I tried many options and filters combinations but I can't generate a small file.

Is there a way to output the waypoint as a single #line (or many 500 coordinate #lines)?
Is there a way to select GPS or barometric altitude?

Another less important question: is there a way to move up-down the track to compensate GPS elevation error (supposing costant)?

thank you,
Valerio