Re: [Paparazzi-devel] platform for agricultural multispectral imaging?

[Chris Gough]

Troy,

In the simplest case, "multi spectral hacking" typically involves 2
(cheap) point and shoot cameras, not a video camera. One is modified
to physically remove the NIR filter (and possibly insert some dark red
glass).
The images from both cameras are post-processed and stitched together
on a workstation after the flight, to create one big mosaic.

Videos are more complicated, probably not what you need to find weeds
or allocate water / fertiliser. Fixed wings take more photos per
dollar. I'm starting a project arround christmas to surveying invasive
species in native bushland, I'll probably be using a ~2kg hexacopter.
ARDrones are pretty small for carying any external patload.

Open question: How to get good time synchronisation between images
(payload linux computer / USB camera) and telemetry (AHRS, fed to
payload linux computer over UART/FTDI)? I assume the telemetry
timestamps are accurate, and that the linux computer is doing an OK
job of keeping time. The problem is that the filesystem timestamps by
on images to have variable delays (~1s), possibly due to scheduling,
congestion and I/O buffering. We figure it's adding ~30m error to our
search and rescue application, which is a significant portion of our
total error budget.

We don't have enough processing power to try a computer vision /
photoprogrametric refinement (It's a realtime application,
post-processing isn't an option). We have already given the camera
driver a very high priority on the OS schedule. Are there any other
"tricks of the trade"?

Is this something custom camera firmware could help with? I thought it
might be possible to get the camera to log accurate timestamps
(perhaps using an external interrupt from PPS on the GPS?). We don't
have open firmware for our current camera, but maybe with a different
camera (running e.g. CHDK) this would be possible?

Chris Gough

On Fri, Aug 3, 2012 at 2:39 PM, Troy Benjegerdes <address@hidden> wrote:
> Too many choices ;)
>
> What I really liked about the ARdrone was the hardware integration, and that
> there's a linux kernel running on it.
>
> I saw a demo of the Quadshot (thequadshot.com), and I'm quite impressed, and
> thinking the best way to go might be to strap one of these to the bottom:
>
> http://www.alfa.com.tw/in/front/bin/ptdetail.phtml?Part=AIPC120M&Category=106193
>
> ... but then I don't quite have a clue where I'd start to to the multispectral
> hacking. At this point I think I just want to fly the camera and record
> 1280x1024 video and then see if it's usefull for determining if I need to
> actually walk out and pull weeds.
>
> On Fri, Aug 03, 2012 at 10:11:12AM +1000, Chris Gough wrote:
>> Hi Troy
>>
>> check this out:
>>
>> http://mechatronics.ece.usu.edu/yqchen/paper/08/08C30_igarss_4051FinalPaper.pdf
>>
>> Some things have moved on a bit since then, but the "hackeds cam
>> packed a foam wing" approach is probably a good place to start.
>>
>> Chris Gough
>>
>> On Fri, Aug 3, 2012 at 2:36 AM, Troy Benjegerdes <address@hidden> wrote:
>> > I'd like to find out what sort of configurations (airframes, camers, etc)
>> > other paparazzi users have used for multispectral imaging. I've got a farm
>> > and for what it would cost me to get a single satellite image, I could put
>> > together quite a nice RC/uav setup with a camera.
>> >
>> > I've played with an ARdrone1 a little bit, but the ultrasonic altitude
>> > sensor gets kinda confused by 5 foot tall corn, and the built-in camera
>> > resolution is pretty low.
>> >
>> > I might be interested in hacking an ARdrone2.0, and pointing the HD camera
>> > toward the ground, but only if I can get Paparrazi running on it instead of
>> > the stock firmware.
>> >
>> > Any other thoughts, or comments from someone who's done this?
>> >
>> >
>> > --
>> > ----------------------------------------------------------------------------
>> > Troy Benjegerdes                 'da hozer'                address@hidden
>> > 7 elements Farm                                         TerraCarbo biofuels
>> >
>> > An Engineer is a man who can do for a dime what any fool can do for a 
>> > dollar.
>> > -anonymous
>> >
>> > If you're going through hell, keep going. ~ Winston Churchill
>> >
>> > The challenge in changing the world is not in having great ideas, it's in
>> > having stupid simple ideas, as those are the ones that cause change.
>> >
>> >
>> > _______________________________________________
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>> > address@hidden
>> > https://lists.nongnu.org/mailman/listinfo/paparazzi-devel
>>
>>
>>
>> --
>> .
>>
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>
> --
> ----------------------------------------------------------------------------
> Troy Benjegerdes                 'da hozer'                address@hidden
> 7 elements Farm                                         TerraCarbo biofuels
>
> An Engineer is a man who can do for a dime what any fool can do for a dollar.
> -anonymous
>
> If you're going through hell, keep going. ~ Winston Churchill
>
> The challenge in changing the world is not in having great ideas, it's in
> having stupid simple ideas, as those are the ones that cause change.
>
>
> _______________________________________________
> Paparazzi-devel mailing list
> address@hidden
> https://lists.nongnu.org/mailman/listinfo/paparazzi-devel



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