“According to the story in the Daily Times, a helium-filled balloon was being used to map the route. The balloon was sent up 50 to 100 feet and held in place with a rope, while surveyors 15 miles away spotted it with high-powered binoculars.”
“According to the story in the Daily Times, a helium-filled balloon was being used to map the route. The balloon was sent up 50 to 100 feet and held in place with a rope, while surveyors 15 miles away spotted it with high-powered binoculars.”