- Angle gauge
An angle gauge is a tool used by
foresters to determine which trees to measure when using avariable 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 awedge prism though it must be held a fixed distance from your eye for it to work properly. Unlike thewedge prism , which is alway held over the plot center, the surveyor's eye is kept over plot center when using an angle gauge.Using the Angle Gauge
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 or BAF. Each tree that is in the plot represents this number, the BAF, of square footage. It is multiplied by the number of trees on the plot to give basal area per acre. In the US BAF is measured in units of Ft2/acre.For example: Using a BAF 10 angle gauge a forester measures 12 trees that are in trees. Therefore, this plot represents 120 ft2 of
basal area per acre.Borderline Trees
Some trees are on the borderline of the plot and must be checked to be sure they are in trees. The limiting distance must be calculated to see if the trees are in or out. The equation to calculate the limiting distance in feet is
Diameter at breast height , DBH, in inches timesplot radius factor , PRF, in feet. Dlim=DBH*PRF For example: Using a BAF 10 angle gauge a forester needs to know the limiting distance for a convert|20|in|mm|sing=on tree. The PRF using a 10 BAF angle gauge is convert|2.75|ft|m for every inch of tree diameter. Therefore, 20 inches * 2.75 ft/inch = convert|55|ft|m. This means that a convert|20|in|mm|sing=on tree must be over convert|55|ft|m away from the center of the plot using a BAF 10 angle gauge to be out of the plot. [ [http://www.kyphilom.com/www/wood/measure.html Introduction to Forest Measurements ] ]References
* [http://www.kyphilom.com/www/wood/measure.html An Introduction to Forest Measurements]
*Avery and Burkhart. "Forest Measurements". Fifth Edition, McGraw Hill, New York, New York: 2002.
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