Andy,

thanks for your report. With Garmin's TIS protocol, we're running
into several limitations that are due to the very coarse nature of
the protocol. For example, direction is only in multiples of 45 degrees.

As a consequence, we explicitly recommend *against* using
a TIS-speaking device as the sole FLARM display in an installation.

We've been in touch with Garmin at the Aero in Friedrichshafen
and invited them to implement the open FLARM specific protocol on their devices. Feel free to ask Garmin about an ETA!

1. The altitude data is often hidden by one of the symbols that define the circle.

Layout of the screen is entirely determined by the display, and there are
probably dozens which implement TIS. FLARM has no influence on that.

2. The displayed altitude is usually 100ft lower that that displayed on the FLARM screen.
May be a rounding issue, I'll check the FLARM part.

3. Perhaps most concerning - the non-direction traffic symbol is never displayed if there is any other traffic (ADS-B or FLARM) being displayed, even if the non-directional target is the closest in distance and altitude.

You probably only had 'informational' (non-threat) targets. FLARM *will* send the non-directional target on TIS *if* it is more dangerous than FLARM or ADS-B traffic
around. In case of non-threat traffic (the most frequent case and what you're
probably seeing) is that there's no threat traffic. In this case
we do indeed prioritize directional targets. The reason is, again, a limitation
of the TIS protocol.


Display of ADS-B targets was very clear and far superior to the depiction on the PF Portable or the Butterfly display. Of course there is a lot more display area to work with. However, several times I saw an ADS-B target on the FLARM display but not on the 396 even though it was in the displayed range.

The TIS protocol is limited to 8 targets maximum and the range (defined
by the protocol) may be lower than the FLARM range. TIS devices may
have their own horizontal and vertical range settings, did you check?

Best
--Gerhard, FLARM dev mgr