Tomorrow evening, September 14, Mansfield University is hosting its first night football game since 1892, back when it hosted the first ever night football game. Some 121 years later, the university finally installed lights at its (“sprint”) football stadium. As a way to kick off the balloon mapping program at Mansfield, I thought we would send up an imaging balloon over the stadium to capture the evening.
After doing some looking, I couldn’t find anyone who had used the Public Labs rig in this kind of a context before. However, I knew that using a mapping balloon at night would provide several challenges, chiefly:
- No real knowledge how the Canon PowerShot A4000 IS camera, chosen for its low cost (~$99 retail), small size (9.5 x 5.5 x 2.5 cm, 150 g), hackability (via CHDK) would handle the lighting.
- No knowledge of whether this odd lighting situation, plus potential wind movement, would allow clear images.
- Potential issues with seeing the balloon and steering it, and avoiding those new lights.
- Lack of familiarity with the venue, possibly problematic when crowded with people.
The athletics department graciously agreed to turn on the lights tonight for a test launch. Around 20 students from the GIS/GPS class or other geography majors came out to watch and help.
Before the launch, I ran a test on the camera to determine its performance parameters in regards to continuous shooting. Memory space was not a problem: armed with a four gigabyte SD card, shooting 12 megapixel JPGs at 2.5mb each simply would not fill the card before the battery runs out. I determined that every 1% of battery power can shoot between 10 and 15 images while testing the camera, a process that led to 1500 images identical to this (click on any image to enlarge):
We launched our first attempt at about 8:02 pm. Because I was too cautious with our limited helium, it didn’t have enough lift and it failed, as did our second attempt a few minutes later for the same reason:
As we filled the balloon again, several of the students took advantage of the camera autofiring to take some pictures. This is how we discovered that we couldn’t get rid of a couple of drops that snuck beneath the top lens:
Since we didn’t have another camera handy, we went ahead and sent this camera up a third time when the balloon was full. The problem now, beyond the dew in the lens, was that the wind had not died down as forecast, so we didn’t get much lift. We only got the balloon up to maybe 150 feet or so because the wind just kept beating it downward. We also got a lot of pictures that look like this:
However limited, though, the test left us with plenty of reason for optimism. The biggest? We managed, even in the worst possible conditions, to get a few relatively clear pictures out of the bunch (if you ignore the dew spots):
After about 20 minutes in the air, and plenty of pessimism that we might not get anything, Brandon Lepley (the student who steered the rig for most of the flight) brought the balloon down.
Lessons for Tomorrow
I think we’re going to be in good shape. The lighting of the football stadium is obviously sufficient that clear pictures are possible, even after a short test. Tomorrow night’s wind forecast is supposed to be very calm, but if it’s anything calmer than tonight, we’ll have no problem getting the balloon up high enough and stable enought to get some clear pictures. I also resolved our other problem, dew on the lens, after we tore down and the students left.
Hopefully, we’re good to go.