Angle gauge

An angle gauge is a tool used by foresters to determine which trees to measure when using a variable radius plot design in forest inventory. Using this tool a forester can quickly measure the trees that are in or out of the plot. An angle gauge is a very similar tool to a wedge prism though it must be held a fixed distance from your eye for it to work properly. Unlike the wedge prism, which is held over the plot center, the surveyor's eye is kept over plot center when using an angle gauge.
Use
When using an angle gauge the user must count trees that are larger than the width of the angle gauge, as viewed from the center of the plot. The angle gauge is held a set distance away from the eye of the surveyor. Most angle gauges have a string or chain that lets the user know the set distance. Each angle gauge is set at a certain basal area factor (BAF). Each tree that is in the plot represents this number, the BAF, of square footage. It is multiplied...