Balloon Mapping From the Ground Up: Public Lab's Field Techniques
cross-posted from PBS's IdeaLab
Public Lab's balloon- and kite-based mapping approach is a new way to take aerial images from the ground. However, there are some considerations and things that can be learned from a few map stories.
Each map project has distinct characteristics in its time, place, and local atmospheric conditions. Here are several examples of how those factors make each balloon and kite map unique.
LAKE MERRITT (OAKLAND, CALIF.)
This map was created on a late July morning. It was cloudy but very calm, which proved important because throughout the flight we had to guide the balloon below and around obstructions and hazards. In order to map the whole area, we had to tether the balloon up and down under various overhead lines, and left and right around oak trees. We walked along the northern lake shore path for most of the flight, but then doubled back through the walking paths.
Walking along narrow pathways through oak trees.
In some cases, the balloon is lowered all the way back to the ground to get around or under things. Proceeding slowly and cautiously is important for staying safe and taking good care of the equipment. When the balloon is flying, somebody needs to watch it at all times. Ideally, a two- to three-person balloon recovery team works together to bring the balloon down where one person is wrangling the line in and feeding it evenly to the tether, and the remaining person works the spool.
Navigating the balloon around the trees.
Three-person balloon recovery team.
UC DAVIS CAMPUS (DAVIS, CALIF.)
This map was made on a foggy November morning in California's Central Valley. We were mapping a police brutality protest, and the fog played a major role in our field work. At the beginning of the flight, we were only able to fly at 200 to 300 feet before being obscured in the fog. In fact, there were news helicopters overhead that could be heard but not seen with the limited visibility.
Flying at 300 feet.
UC Davis Occupy.
After the first hour, the sun started to burn through, and we were able to fly at our goal altitude of 500 feet. The maneuverability and total height control of the balloon tether helped us shoot the best that we could with the foggy weather and low visibility.
SUNOL AG PARK (SUNOL, CALIF.)
While doing a scheduled flight at a community agricultural park, we encountered clear weather with high winds. We could not wait for another time without wind so we flew the balloon, and it acted like a kite; it pulled sharply to the side, a steady angle with the wind. We simply could not get the camera overhead to do orthophotography. So we took note of the steady wind direction, and we walked around the park on the windward side of what we were trying to map.
Map making at an angle in the wind.
CHANDELEUR ISLANDS (LOUISIANA)
Wind can sometimes enable better aerial imaging rather than deter it. While mapping around the Chandeleur Islands in windy weather we let our boat drift off-anchor with the wind swell. The balloon, meanwhile, drifted overhead in the same direction, and we were able to do a long flight over a large area without pulling the balloon around or repositioning it.
In this picture, the boat is drifting along with the balloon. The yellow pin markers are the GPS tracks.
As you can see from the examples above, the ground-based approach to aerial photography and making maps is undoubtedly special in its ability to adapt to all of these different time, place, and atmospheric conditions.