On Wednesday, May 2, 2018 at 7:57:16 PM UTC-7, son_of_flubber wrote:
On Wednesday, May 2, 2018 at 9:23:29 PM UTC-4, Tom BravoMike wrote:
If it's all about software, why can't we have software using the ADS-B transmission (more universal, stronger ergo better visible) to provide us, glider pilots, with the information (visual/acoustic) equal to that produced by FLARM.

I'm pretty sure that it is not 'all about software'. The two other 'biggies' are radio frequency bandwidth (limited) and the rate at which 3-D positions need to be broadcast. Position transmission rate must be limited to avoid saturation of the available bandwidth. To calculate collision avoidance between gliders (that are sharing a thermal), 3-D position broadcasts need to be very frequent, much more frequent than the rate needed for collision avoidance between powered aircraft with nominal separation.

I doubt that ADS-B out transmits frequent enough position reports to compute collision avoidance between gliders. Gliders frequently fly close to other gliders.

Nope. ADS-B Out at ~2 Hz, actually transmits at at higher rate than FLARM. It really is mostly "just" about software. And I'm not saying that to minimize stuff, it's actually very hard to do this well. FLARM has invested a lot of work there to get this far.

So you might ask, 'how come Powerflarm has enough bandwidth to do collision avoidance between proximate aircraft and ADS-B does not?' Part of the answer (I guess) is that Powerflarm uses lower transmission power (so the signal does not travel as far), and there are far fewer Powerflarm transmitters in range of other Powerflarm transmitters, than the number of ADS-B transmitters talking to each other in a Bravo airspace. Another guess is that a Powerflarm transmission is smaller than an ADS-B transmission.

ADS-B has the bandwidth. It's transmitting away all those packers already. That is not the issue... and PowerFLARM itself today works on top of 1090ES In signals just fine.

One ADS-B issue is, as it has always been, the cost of doing ADS-B Out. Both the cost of the transmitter and suitable GPS source.... especially if you want that source to be 2020 Complaint. So doing a software layer similar to FLARM, with as much focus on needs of glider pilots, on top of ADS-B Out needs ADS-B Out adoption in gliders, and then somebody to develop software and build out an ecosystem similar to FLARM and do things like sign up OEMs and integration partners, and... oh my. Just ain't likely to happen is it?

ADS-B transmission is not encrypted, so if anyone would like to try to build Flarm like collision avoidance on top of ADS-B, there is nothing stopping you. I'd love to see that happen, but I'd not under-estimate the obstacles, and I would certainly not delay installing PoweFlarm while waiting for something new to come on line.

Yes, indeed, its all unencrypted, which ends up being an separate issue... for another day. Although spending a few $k on RTCA spec docs will help things go faster. After that it will only take a small fortune of developer time and lots of effort. And if you are doing ADS-B smart stuff the money is not to be made in the glider market.. it's in the GA market today, and maybe large drone/UAV markets. So I'd *really* not hold my breath.