I worked in forestry for about 40 years in the pre-GPS days. Part of that work was in the Puget Sound lowlands of Washington in dense stands of second-growth Douglas-fir, hemlock and cedar. No landmarks and often foggy and/or rainy. We often needed to locate section corners or other property boundaries. For critical work we would use a staff compass and a two-chain trailer tape to measure our way. But, usually we could get close enough (100-200 feet) using dead reckoning with compass and pacing. The GPS I now have isn't too much better than that: it is faster and easier though.