ground cover, buildings and trees: WMO 2010 recommendations, if incomplete, are a sound basis. In addition, Environment Canada, for example, recommends that the screen be placed at least twice the distance of the height of the object, e.g., from any tree that is high. In the northern hemisphere, the door of the screen should always face north so as to prevent direct sunlight on the thermometers. In polar regions with twenty-four-hour sunlight, the observer must take care to shield the thermometers from the sun and at the same time avoiding a rise in temperature being caused by the observer's body heat. A special type of Stevenson screen with an eye bolt on the roof is used on a ship. The unit is hung from above and remains vertical despite the movement of the vessel. Future In some areas the use of single-unit automatic weather stations is supplanting the Stevenson screen and other standalone meteorological equipment. References External links Article - Temperature measurement and the Stevenson screen Example of a non-traditional home built Stevenson screen Measuring instruments Meteorological instrumentation and equipment