Hi Tiago,
Just a real quick reply because no one else ahs ...
On Mon, May 14, 2012 at 4:59 PM, Tiago Gusmão wrote:
> Hello,
>
> It's been a long time since i've posted here!
>
> I'm currently employed in a small company here in Portugal
> (http://www.albatroz-eng.com/). Our main products in a system that
> inspects powerlines from helicopters.
> This year we are going to a big exhibition and i've suggested that it
> would be interesting to have a simulator (only because we would have a
> hard time flying the helicopter inside the building ;) ).
>
> Our solution is basically comprised of a LiDAR, an INS/GPS unit and
> camera(s).
>
> Simulating INS/GPS is easy because all the data is in the FG tree AFAIK.
>
Yes, FlightGear provides "exact" roll, pitch, yaw (true) as well as lon,
lat, and altitude.
> Camera(s) can be linked instances of FG with the views properly set
> (perhaps captured with image server).
>
I've done some work with setting up a model of a pan/tilt camera system
that can point at a specific wgs84 point or along a specific NED vector
(i.e. nadir, or exactly at my shadow, etc.) This was [unfortunately] for a
paid consulting project so that code doesn't live in the FlightGear tree.
However, it's really easy to configure a view that stays locked on a
specific lon/lat and I hacked a small bit of nasal to copy the point you
click on over into the view target variables so you can click any where in
the scene and the pan/tilt camera will hold center on that exact location.
FlightGear offers a lot of flexibility and comparability in this arena.
> LiDAR is the only part the gets tricky. Our LiDAR is placed pointing to
> the side and down of the aircraft. It's a 2D LiDAR that captures
> "slices" of the powerline and as the helicopter flies forward we get all
> the line (like this:
> http://www.albatroz-eng.com/solutions/plmi/lidar_ohl_example.PNG).
> My ideia is to have an instance of FG with the camera pointed as if it
> was the LiDAR and then capture a column of the Z-buffer.
>
> From what i understand FG has depth partitioning. I'm guessing we don't
> want this active for this application. Is this correct? Is there any
> "switch" for this or will i need to dive into the code? The LiDAR has
> about 150m of useful range.
>
> Is there any "recommended" method of getting the values from the
> z-buffer? From what i hear some methods have very low performance. Has
> anyone tinkered with this?
>
FlightGear has the ability to intersect a vector with the terrain and
return the exact altitude of the "hit". This is essentially what we are
doing when we compute the location of the point we click on with the mouse.
However, it may not scale well to the number of intersection tests you
would need to do (per frame) for a scanning lidar system.
Perhaps there could be a z-buffer trick you could use, but I don't know?
Maybe Fred (who's working on shadows and lighting effects) might be the
best one to comment on that since he has his head in that type of code
right now ... (?)
The intersection test code does cache small bits of scenery that was most
recently used, so if you do scan across a line of terrain quickly you might
get a bunch of cache hits and have a chance at making this work, but you'd
definitely need to test it out before putting your eggs in that basket.
I think the problem will be doing this at a resolution that could pick out
individual power lines.
It would be possible to create models of trees and shrubs and connected
power lines and populate an area of the scenery with your custom models --
it would be some effort, but if you can make (or locate) quality models,
the result would be quite nice.
Here's another random idea -- what about "faking" the lidar data or at
least some of it? I'm not sure you would have the performance to
physically model everything the way it is in real life, but if you have the
aircraft location and orientation and an offline DB of your power lines,
perhaps you could compute "fake" lidar data from that using special purpose
code, and that could feed your lidar display?
I'm sure there are several ways you could attack this and it may just mean
picking the best likely approach, diving in, and then seeing how far you
can get with it?
Best regards,
Curt.
For the scenery we would need a powerline with believable trees, shrubs
> and houses below and nearby (and they obviously can't be done with some
> trick that results in no z-buffer entry). The scenery doesn't need to
> match real world locations of powerlines.
>
> Do we have any part of the scenery that is suited for this?
> Last time i've seen we have towers but no cables between them. Is this
> still true? How should we go about solving this?
> I'm guessing i could make the powerline as an extremely big model but if
> it can be done with code i think we would be better served (and it would
> be a nice addition to FG)
> If we could crash into the powerlines it would be a good feature but
> it's not required
>
> As for helicopters, is anyone working on a EC350, EC120 or Bell 206?
> These are the types we have used and so would prefer to have in the sim
> but it's just a minor detail.
>
>
>
> Thanks!
>
> Cheers,
> Tiago
>
>
>
>
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--
Curtis Olson:
http://www.atiak.com - http://aem.umn.edu/~uav/
http://www.flightgear.org - http://gallinazo.flightgear.org
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Exclusive live event will cover all the ways today's security and
threat landscape has changed and how IT managers can respond. Discussions
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