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

[Bernard Davison]

Guys don't forget about the obvious...
Usually Commercial aircraft fly to schedules. They take off at a time and 
arrive at their destination at a time. (We hope. How annoyed are we when our 
flight is late)

Cheers,
Bernie.

Sent from my iPad mini.

On 22/10/2012, at 11:16 PM, Reto Büttner <address@hidden> wrote:

> Hi Chris
> 
> The ATC will work from prior knowledge. The draft rules say on page 7:
> 
> "Prior to each mission, competitors must declare several details about
> their aircraft and how they intend to operate it. Chief among these is
> their preferred cruise speed for their aircraft."
> 
> Regards, Reto
> 
> 2012/10/22 Chris Gough <address@hidden>:
>> Im only just starting to learn about  ADS-B. When my budget SDR kit arrives 
>> (hacked tv tuner dongle) I'll start sniffing the ADS-B and TCAS traffic with 
>> a copy the protocol specs, to try to get my head around them.
>> 
>> With regard to commanding 4D trajectories, obviously the ATC should only 
>> command trajectories that the aircraft is capable off, and where possible, 
>> minimize disruption to it's mission. Do you imagine there would be an naive 
>> exchange of messages to discover the vehicle's characteristics (speed 
>> limits, remaining range, altitude ceiling etc), environment (wind, temp, 
>> humidity etc) and objectives? Or do you think that the ATC should work from 
>> prior knowledge about aircraft characteristics and telemetry logs?
>> 
>> Chris Gough
>> 
>> On 22/10/2012, at 8:33 PM, Reto Büttner <address@hidden> wrote:
>> 
>>> Hi Chris
>>> 
>>> The telemetry message you are imagining does exist. It is the ADS-B
>>> message. It is part of the collision avoidance (separation, TCAS)
>>> functionality.
>>> 
>>> The 4DT part is a simpler and is therefore the starting point of the
>>> contest (L1C). That basic functionality can and should be added to
>>> paparazzi straight forward. Once that is mastered, the a lot harder
>>> collision avoidance functionality can be addressed (L2C).
>>> 
>>> Regards, Reto
>>> 
>>> 2012/10/22 Chris Gough <address@hidden>:
>>>> 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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