EE was walking with a 5 lb. GPS rover pole in his hand. He looked at the GPS to give directions. He was walking on fallen trees. The bark was smooth, wet and slippery. His foot slipped off and rested on soft and uneven ground 18"" to 24"" below, causing him to sustain a sprain of his left ankle. This Report was filed on 11/20/06, I called MSHA to inform internet problem.