News outlets pegged it as the “historic” blizzard of 2015. Snow was supposed to reach unprecedented levels. Flights were canceled, driving bans enforced. New York Mayor Bill de Blasio warned his city to “prepare for the worst.”… The data on snow cover, which have been produced since late 1966, come from the Rutgers University Global Snow Lab, which works with the National Ice Center in Boulder, a joint collaboration with the Navy, the Coast Guard and NOAA to produce the snow maps. The maps are produced mostly with satellite images, in addition to some measurements gathered on the ground by observers, or by checking Web cameras to see where snow is, said David A. Robinson, state climatologist for New Jersey and director of the Rutgers lab.