Chapter 13. Seen from above
Part 2. Reading your report.
Old maps show how the land and its surroundings changed: roads built and abandoned, fields and forest, a town creeping closer.
What it says. The editions of the U.S. Geological Survey's topographic maps that cover your land, oldest first, with their scales.
What to notice. A topographic map shows the shape of the land with contour lines. At a scale of 1:62,500 an inch on the map is about a mile on the ground; at 1:24,000 an inch is 2,000 feet. The larger the second number, the less detail.
If the part is folded. "Old maps and air photos of this land are kept elsewhere; "If you're hooked" says where." Many of Oregon's air photos from the 1930s on are held by university libraries, some free to view online.
In the sample report
The oldest map in the sample is the 1942 Dallas sheet, at 1:62,500; the most detailed is the 1974 Falls City sheet, at 1:24,000.1 The sample found no air photos. Its appendix lists old air photos as "Kept elsewhere" and names where they are kept, starting with Oregon Digital, the U.S. Geological Survey's EarthExplorer and the University of Oregon Libraries.
From the farm's own history (not in the sample report)
By hand, the farm's history found air photos of 1936, 1955 and 1978, kept by Oregon State University and free online through Oregon Digital. In 1955 they show open grassland with scattered trees, where today there is Douglas-fir. Knowing Your Land, Chapter 22, follows the change through all three.2
