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flight path trace in autopilot mode

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flight path trace in autopilot mode

Postby rahulroyrd350 » Thu Nov 05, 2009 5:14 am

I am quite sure that no such feature exists at the moment. I am working with version 1.0.0. I need to know if such a feature is there that will draw the path that the aircraft is going to take in the air when it is in autopilot. Is there any way of achieving this? I need to be able to draw 3d curves eventually within FlightGear for a ground replay system that i am designing. It takes in Flight data from file and runs automatically. Anybody got any idea how to go about this?
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Re: flight path trace in autopilot mode

Postby flameout » Thu Nov 05, 2009 2:49 pm

I don't know how to do this off the top of my head, but I have a few suggestions:

To actually draw the line, I would look at the glideslope marker code, under the data/Nasal directory.

As far as guessing the path the autopilot will take, that will be very difficult. It tries to fly to the given parameters, but guessing where it will go on its way will be difficult.

I hope this helps.
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Re: flight path trace in autopilot mode

Postby MAKG » Thu Nov 05, 2009 5:55 pm

flameout wrote:As far as guessing the path the autopilot will take, that will be very difficult. It tries to fly to the given parameters, but guessing where it will go on its way will be difficult.


Without being very familiar with the FG source code, the usual way to do this is to call the FDM. Isn't that sort of thing exactly what JSBSim is for?

The distinction between a flight planner and a flight simulator is the bounds on the integrations. A simulator will integrate over a frame; a flight planner much longer.
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Re: flight path trace in autopilot mode

Postby flameout » Fri Nov 06, 2009 2:11 am

MAKG is right.

I guess I wasn't thinking entirely straight. There's no way (that I know of) inside FlightGear to do this, but if you are running an external software you could use JSBSim (if that's your flight model) to predict its path, as long as it's a JSBSim autopilot or you can code it yourself in the external program. This will allow you to predict the aircraft's location into the future.

The only way of adding graphics to FlightGear like you are describing that I know of is by doing it however the glideslope markers are done, but I haven't looked at the code recently myself.

I hope this helps.
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Re: flight path trace in autopilot mode

Postby rahulroyrd350 » Fri Nov 06, 2009 3:56 am

flameout wrote:
The only way of adding graphics to FlightGear like you are describing that I know of is by doing it however the glideslope markers are done, but I haven't looked at the code recently myself.

I hope this helps.


Thanks i will make an attempt to see if i can use the glideslope code.

Lets forget about the AutoPilot.
I have Flight Data that is being read from a txt file by an external application and written to the FlightGear property tree.
This file has got Lat, Long and Alt. I think i should be able to convert this to 3d coords within flightgear and plot a path that the flight has taken with a 3d curve.

If someone can tell me any other way to get the 3d curve , that would be really helpful .

Thanks everyone.
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Re: flight path trace in autopilot mode

Postby jonsberndt » Thu Nov 12, 2009 2:48 am

MAKG wrote:
flameout wrote:As far as guessing the path the autopilot will take, that will be very difficult. It tries to fly to the given parameters, but guessing where it will go on its way will be difficult.


Without being very familiar with the FG source code, the usual way to do this is to call the FDM. Isn't that sort of thing exactly what JSBSim is for?

The distinction between a flight planner and a flight simulator is the bounds on the integrations. A simulator will integrate over a frame; a flight planner much longer.


Yes, this is an interesting problem. I worked on the Shuttle Abort Flight Management project several years ago. At each second during the shuttle ascent, several simulations were run quickly to determine viable abort locations at that instant and given the vehicle configuration. It has occurred to me that a JSBSim control <system> could be created that would use a simplified approach to predicting where the aircraft would be in ten, twenty, and thirty seconds into the future, based on current velocities, rates, and accelerations. I think it's possible. It would be a good exercise for someone!

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Re: flight path trace in autopilot mode

Postby rahulroyrd350 » Mon Nov 16, 2009 10:53 am

By editing the code in glide_slope_tunnel.nas in the Nasal directory of the data folder i was able to achieve the desired results.
Now while the patched version of flightgear runs , taking data from an external application, the path taken by the flight is traced out by markers ( a small transparent sphere ) . This serves the purpose and looks really neat. Thanks all.
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