Mee-n-Mac is right ... there is a black & white marker just south of Long Pine Island ... but it's not there in the movie. (In fact, it wasn't there today either!
A winter casualty, maybe?) Maybe they "Photoshopped" it out in the movie, or maybe they just weighed it down below the surface while they made the shot.
Photo Taken Today of Long Pine Island
Billy Going By Long Pine Island