With dusk approaching, the pilot decided to divert to an alternate airport. Information about the airport and its position was found on a GPS database. After making an approach to land, while approximately 3 feet off the ground, the airplane hit a pile of dirt, touched down, and then veered into a wheat field. Postflight inspection revealed the airplane had not landed on the airport's turf runway, but instead had landed on a parallel, 'elevated fill' runway under construction. Runway and construction information was available in the Airport/Facility Directory.