Re: [Paparazzi-devel] 4-Dimensional Trajectories (4DT)

[Chris Gough]

I read the draft rules quickly, and needed to google quite a few terms that 
went familiar to me. 4D trajectory was one of then, and it didn't throw up 
anything that looked like a conventional meaning. I had Imagined (probably 
wrongly) that it was a telemetry message that other planes (and ATC) could use 
as a basis for smart avoiding (or directing) behavior. If it's a telecommand as 
you suggest, in some ways that's a lot simpler (it's just an extension or 
adaption of existing flight-planning constructs).

Either way, the harder part of the rules seems to be robustness to spoofing 
(both GPS and "ghost planes"). Has anybody got experience integrating paparazzi 
with light weight affordable radar? :) I've started reading up on gnuradio, and 
passive (SDR) radar solution looks to me like Mount Everest. Maybe _just_ 
possible for ground/terrain sensing, but other air traffic?

Has anyone used the paparazzi TCAS code recently? Is it up to date with all the 
code changes from the last year or so?

Chris Gough

On 22/10/2012, at 4:56 PM, Reto Büttner <address@hidden> wrote:

> Here are the draft rules:
> 
> http://prod.nais.nasa.gov/eps/eps_data/154025-OTHER-001-001.pdf
> 
> They say:
> 
> Page 3: "Competition missions will be defined by Four-Dimensional
> Trajectories (4DTs), which will be comprised of a series of
> three-dimensional waypoints in space and a specific time of arrival
> for each waypoint."
> 
> Page 7: "The five distinct segments of a mission are: aircraft launch,
> pre-4DT loiter, 4DT flight, post-4DT loiter, and aircraft recovery."
> 
> There will be an air traffic control ("central puppent master"), as
> they want to be able to create specific scenarios for the competitors
> with surrounding air traffic using a combination of real and virtual
> aircraft working synchronously.
> 
> Managing air traffic might be the next step in development of
> paparazzi. I would start out with 4DT. That would be a great new
> feature!
> 
> Regards, Reto
> 
> 2012/10/21 Chris Gough <address@hidden>:
>> I had imagined the 4d trajectories would be chirped about between vehicles
>> to enhance 'autonomous sense and avoid' with vehicles at potentially very
>> different speeds. I need to read the rules more carefully, but I didn't get
>> the impression that a central puppet master was involved. That wouldn't
>> scale well.
>> 
>> Chris Gough
>> 
>> On 21/10/2012, at 9:50 PM, Gerard Toonstra <address@hidden> wrote:
>> 
>> 
>> I'd expect this to be interpreted as a starting time when a uav is *allowed*
>> to be in some location, not so much when
>> it *must* be in some location. My implication is that it's more about
>> devising a strategy where the uav can be kept
>> safely in waiting until it's time to move on. The use case here is that this
>> allows atc to keep an area void of
>> other traffic until the landing of special craft X has taken place or other
>> use cases alike, or that a specific mission
>> may only commence at time Z.
>> 
>> There may also be an additional requirement where a NoFlyZone has a
>> particular time range. You may cross the zone
>> prior or after, but not during, otherwise you have to go around. These NFZ's
>> may pop up at any time during a trajectory
>> and may require substantial replanning of the flight itself.
>> 
>> Replanning flights isn't necessarily bad, as long as it's clear to the
>> operator why it is necessary and what will happen in the
>> new plan. It should also be clear what will happen if the new plan is not
>> accepted, because sometimes the old plan becomes
>> totally incompatible with the new situation.
>> 
>> 
>> Anyway... I'm speculating  :).  The actual rules will define how this should
>> be interpreted. I do think that here's an excellent opportunity to
>> impress the judges by thinking ahead of the requirements and demonstrating
>> that beyond a technical implementation, some
>> thinking has been undertaken why 4D is a necessity and how operators
>> 'interact" with uav's to enable this in the best way
>> possible (maintaining overview of the situation, reducing interaction
>> complexity, etc.)
>> 
>> G>
>> 
>> 
>> On Sun, Oct 21, 2012 at 7:12 AM, Reto Büttner <address@hidden>
>> wrote:
>>> 
>>> I do not think that the calculation of an ETA in flight will be enough for
>>> NASA.
>>> 
>>> I expect rules similar to the following:
>>> 
>>> - Before flight you file a flight plan including 4D waypoints
>>> (position, altitude and time). This calculation must include the
>>> expected wind.
>>> 
>>> - In flight the autopilot must control position, altitude and speed to
>>> hit the filed 4D waypoints.
>>> 
>>> - Perhaps in flight you are allowed to request a change of the filed
>>> flight plan, e.g. if a delay in departure has occured or wind is
>>> completely different than expected. I am sure Air Traffic Control will
>>> allow only a few changes and only for good reasons.
>>> 
>>> Therefore Paparazzi should accept 4D waypoints (position, altitude and
>>> time) and the flight control should be enhanced to hit the time. Has
>>> anybody done that in Paparazzi?
>>> 
>>> Regards, Reto
>>> 
>>> 2012/10/21 Steffen Spies <address@hidden>:
>>>> I think it means, that the flightplan has position and the time. Like
>>>> "be at home at 6pm" while the plane always tells if it will be in time or
>>>> not.
>>>> 
>>>> Am 21.10.2012 um 11:21 schrieb Chris Gough
>>>> <address@hidden>:
>>>> 
>>>>> I noticed that too, and don't really understand what it means. Is does
>>>>> it mean the telemetry messages that say "I am here now, and expect to be 
>>>>> at
>>>>> that place in two minutes"?
>>>>> 
>>>>> Chris Gough
>>>>> 
>>>>> On 21/10/2012, at 6:43 PM, Reto Büttner <address@hidden>
>>>>> wrote:
>>>>> 
>>>>>> Hi guys
>>>>>> 
>>>>>> The newest UAS competition of NASA requests 4-Dimensional Trajectories
>>>>>> (4DT):
>>>>>> 
>>>>>> "The Level 1 Competition (L1C) would focus on a competitors ability to
>>>>>> fly 4-Dimensional Trajectories (4DT) to provide a reasonable
>>>>>> expectation that they will be where they are supposed to be, when they
>>>>>> are scheduled to be there."
>>>>>> 
>>>>>> See:
>>>>>> https://www.fbo.gov/?s=opportunity&mode=form&id=426438809b8348c157fa5b7120c18a45&tab=core&_cview=1
>>>>>> 
>>>>>> Has anyone in Paparazzi realized 4-Dimensional Trajectories, in other
>>>>>> words has included the time dimension in flight control?
>>>>>> 
>>>>>> Regards
>>>>>> Reto
>>>>>> 
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>> 
>> 
>> --
>> Gerard Toonstra
>> -----------------------
>> http://www.radialmind.org
>> 
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