What I want to do
The topic of balloon mapping at night has come up a couple of times recently. Andy Shears and his students at Mansfield University did some really beautiful work taking pictures of MU's first nighttime football game in over a century in September. However, that seems to be the only nighttime mapping using Public Lab tools that anyone seems to know of and it seems like it would be an exceptionally useful tool for mapping light pollution.
I've got a balloon mapping outing planned for the end of the month that presents the opportunity to tryout nighttime mapping. So, I'm working out what I would need to do this safely. (I'm sure someone will promptly explain to me the legal reasons why I shouldn't do this at all...)
My attempt and results
My plan is to toss a package of LED balloon lights into the balloon when it's being filled. I'm also going to light the line by attaching glow sticks to it every 50ft or so. I'm planning to use my faux-FABA rig to carry the camera because it will block the camera from the lights in the balloon. I'm not really sure that's a necessary step, but I figure it couldn't hurt. Additionally, I'm not planning on flying more than 400ft up. Other than that, everything will be standard balloon mapping protocols.
Questions and next steps
The questions I have about doing this are:
1) Is this legal/ how do I do this legally?
2) How difficult is it going to be to stitch mostly black photos?
3) Will the camera be able to capture decent pictures of ambient lighting? The football field worked well for Andy, but those were some pretty strong lights.
4) Provided the pictures turn out, how do I quantify the light pollution? Do I even need to?
If this works, I'm thinking of making a nighttime map of the University of Kentucky campus. There's been a lot of work done on campus safety recently and it would be interesting to see the overlap of the new security measures and nighttime lighting.
4 Comments
For an after dark flight you might want:
The all black photos will be a problem to stitch or assign to even a general area. The higher you fly the fewer photos there will be without any lights in them.
In advance of the flight, take the camera out after dark sometime and see what it can capture on campus using different settings.
For a late afternoon flight that continues until after dark, the exposure settings are problematical.
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sounds like you are following the FAA guidelines for 101.17: http://www.ecfr.gov/cgi-bin/text-idx?c=ecfr&sid=e29bc663738a4224a2112f8a1a8279a9&rgn=div5&view=text&node=14:2.0.1.3.15&idno=14#14:2.0.1.3.15.2.9.4
§ 101.17 Lighting and marking requirements. (a) No person may operate a moored balloon or kite, between sunset and sunrise unless the balloon or kite, and its mooring lines, are lighted so as to give a visual warning equal to that required for obstructions to air navigation in the FAA publication “Obstruction Marking and Lighting”.
(b) No person may operate a moored balloon or kite between sunrise and sunset unless its mooring lines have colored pennants or streamers attached at not more than 50 foot intervals beginning at 150 feet above the surface of the earth and visible for at least one mile.
(Sec. 6(c), Department of Transportation Act (49 U.S.C. 1655(c)))
[Doc. No. 1580, 28 FR 6722, June 29, 1963, as amended by Amdt. 101-4, 39 FR 22252, June 21, 1974]
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Agree 100% with castle's camera recommendations. We did highest ISO our little point and shoot had (1600), shutter priority, manual focus to infinity.
Your biggest challenge, even in shutter priority mode, is movement of the camera. We did get some good imagery on the periphery of our map in areas much darker than the football field, but we collected many that were blurred because of movement in just 2 mph winds. With perfectly calm conditions, a point and shoot could accomplish exactly what you're trying to do.
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Andrew -- good point about motion blur. I see your nice shot of the stadium was taken at 1/20th second. Last night I tried to take cityscape photos from a plane window at night and got mostly black at 1/125th second. So my recommended 1/160th second probably won't work for most night scenes with a Powershot because the sensor is not sensitive enough.
If Jessi wants to quantify spatial variation in light levels, the exposure should be constant for all photos. So manual lock of both aperture (wide open) and shutter speed (probably pretty slow) is required. This assumes all shots are after it becomes dark outside. Very calm ballooning conditions will probably be needed.
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