Flutterby™! : Aerial Photography... Coming closer to fruition 2003-06-10 18:48:33.985578+00

Aerial Photography... Coming closer to fruition

2003-06-10 18:48:33.985578+00 by ebradway 13 comments

I'll be getting my grant money July 1 and I'm trying to hammer out some of the details. Some important things I've learned since:

The rig won't need to go much higher than about 80m. This changes the design radically. I'll will attempt to use stranded cat-5 as my tether and run 12V DC over one pair.
After reviewing Canon's offerings, I found I can't do everything I want unless I buy a PowerShot S series (the S45 is about $500). So I'm looking at the photopc library for Linux but I'm not familiar with Epson's or Fuji's camera offerings. Using photopc means I can run Linux in the gondola (+geekpts) and use a solid state Flash drive.

I've got a laptop running Win2K for the basestation. I'll probably setup a webserver in the gondola computer and build a web-frontend for the camera and other gear. I'm just wary of USB support in Linux. Photopc talks alot about serial but that's way too slow for what I want. I also need a good altimeter and would prefer something the PC can read. I'll play with putting a GPS in the ballon, but GPS sucks for accurate elevation readings (+/- 20m).

Nathan (whom I don't think you've met, but I can put you in touch with if necessary) has run lots of cameras off a single computer with Video4Linux

to do time-lapse experiment monitoring, but those were just webcamse, so that's probably not useful to you.

Have you looked at gPhoto? They seem to have decoded quite a few cameras. And don't be too scared of USB, the last few things I've tried with it under Linux have mostly just worked.

Oh yeah, the ACS CF adapter is only $20, versus the "starting from $39" on the link you used. Of course I didn't check to see if that actually included the CF card.

The ACS is perfect - and cheaper. I don't want the 3.5" drive housing. This means I'll have another $20 to spend on a larger CF card! Do you know of a cheaper source for the VIA Eden EPIA 5000? I need the USB riser, DC converter and AC adapter.

I was under the impression that gPhoto was just a Gnome or GTK interface on top of pcphoto. I guess I need to take a closer read.

As far as altimeters go, I'm beginning to think I need a watch. This has a serial interface and is very light. I could use it in datalog mode (it has it's own memory) but it would be cool to get it spooling altitude data out the serial port. This blows my budget, but I really do need a new watch. I could go alot cheaper and mount it so it shows in each picture. Or even sillier, buy a cheap digital camera pointed at the watch and write some recognition code to read the altitude, time, and facing.

gPhoto does look like it's the way to go. And it expands my camera choices alot. What I want to be able to do is take 'preview' pictures and final images. I'll play around with my A10 and gPhoto at work tomorrow.

I could be wrong about gPhoto, last time I looked at it could have been before all sorts of restructuring and similar code issues. Haven't run into a cheaper source for the motherboard, but if you have academic pretensions have you called up Via

yet to see if they might help a bit? I talked to their rep (sorry, no card) at the Embedded Systems Conference

and got the impression that they might be willing to help on projects like that.

Also, for data acquisition, Dallas Semiconductor

seems to have a fairly liberal samples program, and it looks like a lot of folks have built barometric pressure sensors around the Motorola MPX4115, less than $20 from Digi-Key. I haven't looked at interfacing to it, but for $350 you could get that chip, an Atmel dev kit and a few CPUs, and a couple of support chips.

As Dan stated I helped a friend with a long term experiment that used 8 USB webcams hooked to one Linux computer (Redhat 7.2) to monitor/record fish over a period of months. USB on Linux is generally pretty good now, but I suggest using a recent 2.4 kernel. Avoid development kernels (2.5) if you can. They have a habit of biting me in the ass...

There were some USB quirks that I mostly blame on the cheap $15 webcams and the very moist environment. The Kernel would lose an interrupt and panic or lock up once in a while, but some watchdog software helped it reboot gracefully. If this is a monitored experiment then you probably wouldn't need to worry.

The one concern is finding a camera that has good Linux driver support. That can be a pain. Also, if you are doing streaming video, don't plan on running more than one camera at a time on a single USB 1.1 controller. The bandwidth isn't there and the drivers/cameras would tend to freak out. Shut down the first camera before starting up the next.

Instead of spending hundreds on a watch with an altimeter I would take Dan's suggestion and build/buy a simple circuit and hook it up to the serial port on the balloon's motherboard. Googling for "digital altimeter circuit" and "serial port altimiter" shows a few plans. Or, if you do have the money to spend, one of the high end etrex GPS units has a built in altimeter and has a serial port. I think these would generate better results than trying to fit the watch in the camera's picture.

I just fired up gphoto2 on my new ArcIMS server (Red Hat 9) with the Canon A10 hooked up. The gphoto2 doesn't support remote capture on the A10. This means the A10 won't work for the project if I use gphoto2 (Canon uses a proprietary protocol and doesn't share). I'll stear away from Canon from now on...

Has anyone had much experience with Fuji's offerings? Fuji mentions 'effective pixels' and 'captured pixels'. I don't want alot of in-camera image processing. I just a decent lens and CCD - and I need to know the true resolution of the CCD. I also don't care about zoom - I'll use the height of the balloon to control the image resolution. I want to keep my focal length fixed (and I have to know it - accurately).

The problem with using a barometer for altitude is that it has to be calbrated on the ground and I need some way to determine the elevation. I'll have to look into it some more. Suunto does make an altimeter watch for $150 but I would really like to get the computer logging the altitude with the image.

Hmmm... I just tried a Canon A60 - which supports the PTP protocol but won't capture previews or images. The minimum requirements for the project would be 'capture image' but 'capture preview' would be nice as well. gphoto2 does work quite well though. Definitely changes my plans for the OS in the gondola!

Fuji's "effective pixels" thing comes from the fact that they skew the sensor out of a strict square raster pattern, so while the image isn't really getting the number they claim are effective, it's getting more than a strict look at the pixels might suggest. Supposedly. I haven't played with the S2 beyond "Great, I can get a ~3 megapixel image out of it fast".

Yes, barometry sucks for altitude, but your alternatives are sonar (off-the-shelf solutions only seem to be good to 20m or so, and I'll bet wind shear plays hell with accurate readings) or some sort of radar solution (reflecting a signal down the cable will just give you cable length, which you already know). The watch doesn't say how it does altitude, but I'll bet it's some combination of GPS and atmospheric pressure. And at tens of dollars for a sensor, you can build one for the gondola and one for the base-station and look at differences.

Hmmm... Looks like the gphoto2 that comes with Red Hat 9 is a good bit outdated! Evidently the Canon A10 supports capture. What I have installed doesn't even recognize the A60...

Now for some nasty thoughts about Red Hat as I try to build a program from a CVS tree as opposed to a Red Hat RPM (gphoto2 is spread out throughout the file system just like everything else in Red Hat...).

<sfx type="whistling" mode="innocently">On Debian we type apt-get source <packagename>, which drops the built source tar with diff files right in our laps, into which we can then untar the current versions and apply the diffs</sfx>

I'll use Debian or something even lighter for the gondola. I'm just testing now...