It took a couple of weeks for Jeffrey Warren’s message to sink in. At first I thought his workshop on balloon aerial photography at the Fine gigapixel conference in November promoted a fringe pursuit – lofting cameras on tethered helium balloons to make better maps than were currently available. But this pursuit emerged from the elegant convergence of modern camera technology and traditional lofting methods (balloons and kites). It was now possible for anyone to make good, current “maps” from stitched, low-elevation vertical photographs. Jeffrey is committed to inventing workarounds to the technological and financial obstacles that would otherwise put this process out of reach of the communities that might benefit from good maps. This was the focus of his thesis at MIT, and he has had great success bringing communities together around these new map images and the experience of making them. He has made the objective so compelling, and the process so simple and inexpensive that I soon realized I had to try it.
So I started looking for the materials I would need. It was easy to buy Mylar sleeping bag covers which are used for helium balloons (three will lift a camera and cost ~$3 apiece). A kite was more expensive but easy to find because the Sutton Flow Form 16 ($100) is widely used and every search leads to it. Finding kite line was harder because braided Dacron comes in many strengths and colors and there is conflicting information about which is appropriate. Kitebuilder.com had a $10 sale on 3000 feet of pink 50# test (probably good for ballooning), and I also got 3000 feet of brown 150# line for $30 (probably good for kites, but maybe 200# line is better?). I ordered a kite line winder for $10 at sourcingmap.com, and when it arrived 49 days later (shipped from Hong Kong over the holidays) I was offered a $5 discount on my next purchase if I wrote a review. My honest and insightful review (“…a source of very good deals on many items, and a fascinating business model…”) was published and I used the discount on a second kite winder which arrived in 12 days.
I was gearing up to do both balloon aerial photography (BAP) and kite aerial photography (KAP). Ballooning is easy and Mylar sleeping bags are cheap, but balloons will not lift very heavy cameras and don’t work when there is much wind. Plus, helium has to be purchased for every day or two of flying at something like $80 per fill. Good kites are expensive but are flown for free, are the only option on windy days, and have the potential to lift bigger cameras along with a mechanism to point them at any angle.
Figuring out which camera to buy slowed me down considerably. I don’t own a point and shoot (P&S), so I was ready to start bidding at ebay for an appropriate model. Jeffrey Warren’s Web site and discussion forum do not have much information about specific cameras. I guess this is because the minimize-the-obstacles approach is to use any small, cheap camera. But I assumed certain models would be better than others, and there are hundreds to choose from. To make BAP and KAP simple there are a few primary considerations:
1) Weight. When ballooning, everything is easier when the camera weighs less than 150 grams. With enough kite and wind, big DSLRs can fly, but even KAP is easier with smaller cameras.
2) Cost. Kites crash and balloon tethers fail, so spending a lot on cameras is not for beginners.
3) Continuous mode. The first level hack for taking multiple photos during a flight is to wrap a rubber band around the camera so the shutter button is depressed and the camera fires continuously (about once per second in P&S cameras). The camera must have a mode for this.
I guess that’s just too easy for me, so here some other considerations:
1) Sensor. This does not matter too much because the lenses on little P&S cameras rarely outperform a 5 megapixel sensor, especially when dangling midair. So any 5 to 10 MP camera could work. Ideally, one could use a 12 MP camera set to capture 6 MP images so the extra pixels would eliminate the need for Bayer interpolation (which adds noise), but I don’t know how to find out if a camera does this. It could be difficult to capture more than about 20 overlapping images to stitch together, so the final image may not be large enough to upload to gigapan.org (50 MP minimum). Reaching this limit with fewer photos could be one advantage of using a 14 MP camera. Also, some newer cameras with more MP might also have better lenses and better image stabilization.
2) Image stabilization (IS). This would seem to be a really good feature for this application, although it is designed for shaky hands and not wildly swaying cameras. Some of Canon’s 7 MP to 10 MP Powershots from 2007-2009 have lens-shift IS, and some don’t. I assume newer cameras have better IS, but I don’t plan to fly a very new camera.
3) Exposure modes. I assumed a manual exposure mode would be a desirable feature so all the photos can be taken with the same exposure for seamless stitching. This is the standard protocol for making gigapans. However, you can’t set the exposure while viewing the scene during a balloon flight, or change the exposure (or pause) if the sun peeks out mid-flight, so automatic exposure is often the best choice. While flying, it is important to keep the shutter speed high, so a shutter priority mode (Tv or S) might be preferred. This feature is rarer than image stabilization on Canon’s Powershots, but it is present on some.
4) Power source. Freshly charged batteries can fire a camera continuously for an hour or more; often long enough to fill up the memory card. Multiple batteries are required if you want to make multiple long flights in a day, so you must choose between having extra AA batteries (rechargeable or not) or having extra Li-ion battery packs (for your particular camera). Some P&S cameras use AAs and some use battery packs. Both are readily available for similar prices.
5) Focal length. Most of this aerial photography is done with fairly short (wide angle) focal lengths, especially if you want the photos to overlap enough for stitching. It would be possible to make higher resolution images with longer focal lengths, but precisely pointing a dangling camera is a challenge. The standard protocol is just to walk around with the tethered balloon or kite while it is firing away and hope the camera captures the area you want with no gaps. Most of the cameras have an appropriate focal range for this (e.g., 35-120 mm eq).
I have been using the Canon Camera Museum to find candidates. For a balloon camera, the Powershot SD1100 looks reasonable (8 MP, 125g, IS, but no Tv mode). I bought one on ebay for $52 (incl. shipping). It is hard to find a Canon under 175g with Tv. For kite photography, the Powershot A590 is a minimal candidate (8 MP, 175g, IS, Tv). I bought one on ebay for $71 (incl. shipping). I am still not sure if these are good choices.
And there is another level of complexity to the camera decision. The function of most Canon Powershots can be enhanced with a free program called CHDK (Canon Hack Development Kit). CHDK loads on startup from the SD memory card (it’s easy to install it there) and adds a deep menu structure of powerful features including shooting in RAW, USB-cable remote shutter-release, motion-detection trigger, shutter priority mode, exposure and focus bracketing, and custom continuous mode. So with CHDK, the camera does not have to ship with a Tv mode to have a shutter priority mode. With CHDK the shutter can be triggered electronically through the USB port (my Nikon D40 DSLR can’t do that). Scripts can be written for CHDK to do specific things like releasing the shutter every 10 seconds (instead of every second with the button mashed down), so far fewer shots are wasted. Installing and learning CHDK is a potential obstacle to easy participation in aerial photography, but I installed it as soon as the ebay cameras arrived. It displays the CCD temperature!
To take vertical aerial photos for stitching into a map image, the camera should point straight down. Jeffrey has designed a no-cost suspension using a 2 liter soda bottle which he and others have repeatedly used with success. But considerable engineering effort has been directed toward hanging cameras from kite lines, and one can buy a rig with self-leveling suspension (Picavet) and electro-mechanical equipment for pointing and triggering the camera. I thought this was way beyond my intention until I saw Brooks Leffler’s Brooxes Basic KAP Kit for only $72.00. This rig has everything needed to suspend itself from a kite line, automatically rotate the camera in 30° increments, and trigger the camera at each position. If only it would tilt the camera as well as rotating it would be flying GigaPan. A kite can’t hold the rig in exactly the same place long enough to take a precise GigaPan-like panorama, but if 1) it is high enough above the ground so that some wandering is tolerated, and 2) there is plenty of field-of-view overlap between adjacent camera positions, and 3) the rig continues to rotate and repeat the 360° capture several to many times, it should be possible to capture enough images to make stitched 360° panoramas. As I browsed further I learned that others had thought of this before and that by adding an AuRiCo controller and a second servo motor for tilting, the Brooxes rig could take four-row panorama sets with adjustable increments. It was indeed a flying GigaPan imager. Stitched high-resolution maps are a worthy goal, and any oblique photo from midair can have potential, but the promise of low-elevation aerial 360° gigapans was irresistible. I ordered the full AuRiCo rig (about $300).
I fear that I have abandoned Jeffrey Warren’s mission. That might be okay because as far as I know I am not part of a beleaguered community in need of better maps. I learned of the potential of BAP and KAP by accident (Jeffrey’s talk at the conference followed mine), and I decided to pursue it only because Jeffrey had removed so many of the financial and technological obstacles. Now that I have put those obstacles back in place, it is not clear if I am ever going to get to the part where I capture aerial images. I could put my Powershot in a soda bottle and fly it from my Flow Form kite today, but instead I will wait for my Brooxes kit (assembly required) and see what I can make of it. It’s not an obstacle when you choose it yourself. Right?