Joe Bollinger in Glen Burnie asks: "How is snow measured at an unmanned weather station?" Some aim a video camera at a ruler. But the National Weather Service uses humans. Snow falls on a white, plywood "snow board," and is measured with a stainless steel ruler. The board is wiped clean every six hours. BWI's weather station is unmanned, but its snow board is tended by a control tower employee under contract to the NWS.