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2003-05-15 17:46:13.094449+00 by ebradway 11 comments

I'm starting to shop for the parts for my Summer research project - flying a PC and digital camera with helium ballons to take georeferenced digital aerial photographs. I've been looking at Mini-ITX motherboards like Dan's Via Eden. Because of power consumption concerns, I'll probably go with the EPIA 5000 (fanless). I don't need alot of CPU horsepower. Has anyone tried out the FIC Falon? I'm wondering how well it works as a home PC. The lack of USB 2.0 is a drag - but $150 for a system that'll play DVDs and MP3s without a hard drive or OS is pretty swank!

[ related topics: Music Photography Coyote Grits Aviation Embedded Devices - Via Eden Gambling ]

comments in ascending chronological order (reverse):

#Comment made: 2003-05-15 20:37:26.643193+00 by: ebradway

To restate the problem: get a digital camera of at least 1Mpixel about 100m in the air, pointed straight down, and control the shutter from a laptop on the ground.

Here's my best possible solution so far: Use 2m helium balloons (about 7lbs lift per balloon) tethered to a base station containing a laptop and GPS. Suspened from the balloon is a 'gondola' with a consumer digital camera and a PC of some sort. The PC is running the camera's remote control software and VNC server. The laptop in the base station is running VNC client. Problems looked at so far: USB has a normal range of about 10m. To go much beyond 25m costs about $750 for a repeater - this blows my budget. I did mention that I have a budget of $1000. So the idea is to use either wireless ethernet or even use Cat-5 (or even Cat3) as the tetherline. I'm also playing around with providing power to the gondola through the tetherline (the basestation will be equipped with a 12V deep-cell marine battery and an AC inverter.

Other possible solutions: a camera I haven't seen with wireless ethernet builtin (and at least a 1Mpixel resolution), a better (cheaper) way to get a payload 100m in the air stable enough for photography (and cheap enough to do regularly and doesn't require alot of skill to operate - this eliminates kites and remote control airplanes). Here's the price breakdown of the current best idea (assuming I can provide power over the ethernet cable):

ITX motherboard, RAM, hard drive: $200 Ethernet cable: $50 Custom power supply: $50 (provide 5V, 12V to motherboard and hard drive and 6V to camera) Digital Camera: $200 (Canon A40 - for various reasons I won't go into now) Helium Tank: $150 Balloons: $30/each (4 to begin with) GPS: $130 Gonodola (assembled from diamond plate aluminum and plexiglas): $50

Everything else I already have. Anybody have any ideas?

#Comment made: 2003-05-15 22:02:36.668086+00 by: Dan Lyke

100m isn't very far. I also assume that you need to get GPS simultaneous with the image acquisition? And do you need to see what you're taking pictures of, or can you do that part blind? And how many images will you need to acquire?

One possibility would be just build a physical shutter release and use a stock off-the-shelf radio control system, save to the CompactFlash. Actually, using video out and one of those 900MHz video transmitters for previewing, then just saving to CF, sounds like a reasonable approach. Some of those claim ranges that could work, especially if you put some sort of directional antennas on 'em.

The Canon A40[Wiki] is a good little camera, works well with the USB remote control software. Much better for remote control apps than the D-30 and D-60 actually.

#Comment made: 2003-05-15 23:01:50.037377+00 by: dws

If you're only 100m up, you can do GPS from the ground, though you might get better accuracy by having the GPS above tree-line.

#Comment made: 2003-05-15 23:07:37.487595+00 by: dws

By way of tossing in an idea from outside the box, various kit people have rigged up ways of using Pencams for arial photos. You don't get the benefit of ground control, but the pencams are light enough that you hoist multiple of them aloft.

http://www.gentles.milestonenet.co.uk/KAP/Pencam/pencam.htm shows one hack. Googling for "pencam kite" will turn up more.

#Comment made: 2003-05-16 12:15:09.635516+00 by: meuon

Nice kite pics.. Wow.

#Comment made: 2003-05-16 13:36:58.051275+00 by: ebradway

Dan: One of the design goals is to be able to essentially 'look through the viewfinder' from the ground. So the radio control system is out of the question unless I could somehow rig the video signal to the back-panel LCD to broadcast over 900Mhz... Hmmm....

I just found the Canon A300 (new model). $189 at Amazon. 3.2Mpixels. Lighter than the A10 and runs on 3V (two AA). It would suck for general photography compared to my A10 - only digital zoom, short battery life, etc. But I'm not using any zoom. I want fixed infinite focus. And I have external power.

DWS: Yes, the GPS will pretty much have to be in the base station. In order to see the accuracy I want, I'll have to keep the GPS stationary for at least 10 minutes. Impossible to do at 100m in the air! The current plan is to mount an large umbrella on the base station with a big red dot and an arrow on it (which I'll point north) and make sure the base station is in each picture.

I bought the Aerial Eye CD-ROM last year to investigate using a kite. For a couple hundred dollars, I can get a fairly stable kite with about 5lbs of lift. But kites require alot more skill to operate than balloons. The hardest part of flying a balloon is making sure it doesn't get away!

#Comment made: 2003-05-16 14:51:46.766157+00 by: ebradway

If you liked the KAP images, check out Burningcam

#Comment made: 2003-05-16 16:26:51.970271+00 by: Dan Lyke

Eric, I haven't checked to see what it outputs, but the Canon cable set comes with one that has an RCA plug that I assume is outputting NTSC. If your positioning is ground based anyway, then I'll bet you can rig a small transmitter for the viewfinder, and just trip the shutter mechanically. This could also monstrously lower your payload and tether line weight.

If you do go with the full machine, last time I looked the GPhoto folks had decoded most of the digital camera USB protocols, so you could put Linux[Wiki] on CompactFlash[Wiki] and have no moving hard drive in the payload.

Two dots on the ground, if widely separated, could give you direction and altitude, the wider the separation the better, but this guy appears to have got reasonable distance tracking using dot size.

#Comment made: 2003-05-16 17:50:24.194816+00 by: pharm

I've got a Canon A70 -- bigger brother of the A40; it will indeed spit PAL or NTSC out.

Thought: rather than ethernet / usb why not use a serial card with real (ie not crappy PC style :) ) buffered serial interfaces and use a simple twisted pair serial line as part of the tether? Should be good for 4-5000 ' at a guess. Might not be fast enough for you though...

#Comment made: 2003-05-16 18:33:48.93007+00 by: Dan Lyke

Here's a 2.4GHz wireless system claiming 3 miles (with directional antennas) and a tiny transmitter that broadcasts on TV Channel 59 (and runs off a 9v transistor battery! Yay low weight!) that's got a short range (200 feet), but might be improved with directional antennas, and a 2.4GHz system with IR repeater and 300 foot range for $120. Although the repeater only seems to have half the range. Damn.

Here we go: 500 feet for $190, get a USB video decoder that you can plug into the laptop, a cheap R/C system (use the extra channels for aiming)...

Of course this still demands building something in the base station, and... well... there are things you can't do without the computer up there.

#Comment made: 2003-05-19 14:10:59.916828+00 by: ebradway

My A10 doesn't do NTSC, so I'll have to wait to get my hands on another camera to play around with the other solutions. As far as weight is concerned, except for the power source, I'm not sure if a system with a 2.4Ghz transmitter and a servo system for taking the pictures will really be significantly lighter than the ITX motherboard solution. Not to mention, the idea of flying an entire PC with a balloon is kewl...

I did some more research and the commercial outfits doing similar photography never go about 200ft. They claim that they get all the coverage they need and better resolution at the height. Oh yeah, I already have commercial georectification and photomosaicing software. I've also found that urethane 'blimps' are preferable over ellisoidal balloons because they are more stable in windy environments. Also, the urethane is much hardier than latex ballons (i.e., I'll be able to resuse the urethane blimp more than that balloons). I can get a misprinted blimp for less than $100 from the folks selling advertising blimps.

Another thing I didn't realize is that there are about 50 companies around the US who do this kind of thing. But they use bigger blimps with more elaborate camera systems (combination of video for aiming, digital and film cameras). Most all are tethered using RC controls to activate the shutter. What I'm doing is fairly unique - but might also lead to a nice little side job while I'm in school!

As far as altitude and direction goes, I'll probably mount a small compass, clock and altimeter inside frame of the picture. This in many ways greatly facilitates analysis of the image. They will the mounted on the outer edges of the picture frame where any imagery is so far off nadir to not really be useful.