the pilot in commands' failure to obtain obstruction clearance from trees during a visual takeoff from a short, soft, wet field in instrument meteorological conditions. A factor was the pilot in commands' misjudgment of the takeoff climb performance of the airplane, which resulted in striking trees at the departure end of the field. A second factor was the operation of the airplane with a known defective wet compass, which resulted in the pilot's disorientation and led him to land in the unsuitable field.