Two hundred years ago, “metes and bounds” surveys used distances from trees, posts, rock piles or natural features to describe corners where property line directions changed. Trees were used as markers for the corners of a parcel, and these descriptions were included in deeds.
You can read more about Thomas-Van Gundy's efforts in an article by Jane Hodgins published in the United States Department of Agriculture web site at http://goo.gl/i7gpJ. The dataset she is using is available at http://www.nrs.fs.fed.us/pubs/gtr/gtr_nrs101.pdf.
My thanks to newsletter reader Wendy Stevens for telling me about this article.