Dyer has it right. A staff compass is a precision compass of the sort that came with a transit. It has a level bubble and a needle about 4" long and sighting leaves. They come with a ball socket on the bottom that fits an ash wood (Jacob's) staff that is pushed into the ground. Carefully used, a staff compass and the "Jake stake" will give bearings to 30 minutes. A two chain trailer tape is a metal tape that is 132' (two chains) long with a trailer marked in topo units (a topo unit signifies one foot of rise per 66' chain). In use, one would run the tape out to a 2 chain distance and then measure the slope using an Abney Level scaled in topographic units. The forester would then advance the tape to the appropriate topo mark on the tape trailer. All of this was done to correct the distance on the slope to horizontal measure. All mapping and surveying is based on horizontal distances. Yeah, I know this is a bit arcane but most of the western US was surveyed this way and in forestry the old surveys rule.