I dont think the issue is with close targets, and I dont think we are talking
about long periods of "filtering" in which the glider can drastically change
position. We are talking about few seconds, maybe 10 seconds the most, not
sure. Basically the butterfly displays handles missing transmissions, while
xcsoar flarm radar doesnt, and as a result the targets keep dissapearing. I
cant see how this can be desired.
However I understand this might be more difficult to implement.
Ramy
>________________________________
> From: Michael Huber <michaelg.hu...@gmx.at>
>To: David Anisman <david.anis...@gmail.com>; xcsoar-user@lists.sourceforge.net
>Sent: Tuesday, September 11, 2012 11:48 AM
>Subject: Re: [Xcsoar-user] Flarm radar
>
>>The principle of what's been referred to here as "filtering" is based
>>on the fact that
>>if a glider is, say 2km from you (as per a flarm transmission) and if
>>a flarm message
>>is transmitted once per second, then if the receiving flarm fails to
>>receive a transmission
>>a second later with an updated position, this obviously does not mean
>>that the glider just
>>vanished, it is obviously still there somewhere probably still close
>>by.
>>So the question is: what to display in that case?
>
>The issue is not with a glider that is 2km away. Filter it or not,
>keep it on the last known position for a few seconds or try to predict
>its position from its last vectors, it doesn´t matter much as long as
>it is still 2km away.
>For a glider only 200m away or even in the same thermal it will make a
>difference. When no transmission is received some clever algorithm may
>predict that the other glider is still circling with a constant turn
>rate like a few seconds before, while in reality he decided to leave
>the thermal and dashes through the core right next to you.
>
>"After a short distraction, you realize that you have lost sight of
>the other glider thermalling with you. You immediately check on your
>[superclevermotionpredictingbrand] FLARM radar and see he is now in
>your blind spot, but still circling nicely with a constant distance
>from you. You start to relax as you suddenly hear a loud bang..."
>
>If no FLARM transmission is received, then no data is available. Even
>the best motion prediction algorithm in the world can´t change that.
>If any predicted data was shown on the XCSoar FLARM radar, it should
>be immediately evident that this is predicted only, and not actual
>data.
>
>Michael
>
>
>
>
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