I mostly use my GPS for navigating backcountry, forest service roads. City Navigator is pretty good for this, but I've found that several roads shown on it in my area are in fact closed. Others are incorrectly identified. The forest service has issued new "motor vehicle use maps" for many areas. Is it possible ot edit the CN maps and erase closed roads or rename others? Or to create new, routable roads from known (track) data?