Angle Gauges and Wedge Prisms for Basal Area Sampling
Angle gauges and wedge prisms are the primary tools for variable-plot sampling (also known as prism cruising or Bitterlich sampling) — one of the most widely used methods in professional timber cruising. CSP Forestry carries angle gauges and optical wedge prisms in multiple basal area factors (BAF), allowing foresters to efficiently estimate stand basal area and volume with statistically valid results. These compact, rugged instruments are a staple of every timber cruiser's vest pocket.
Complete your timber cruise setup with clinometers for slope and height measurement, diameter tapes for DBH recording, increment borers for site index, cruiser vests, and tallying supplies. CSP Forestry has supplied professional timber cruisers since 1986 with the forest measurement instruments that drive accurate stand assessments.
Frequently Asked Questions
What is an angle gauge used for in forestry?
Angle gauges are used in variable-plot timber cruising (Bitterlich sampling) to determine which trees are "in" or "out" of a sample based on their diameter-to-distance ratio. Trees that subtend an angle wider than the gauge are counted toward the basal area estimate.
What BAF should I use for my timber cruise?
The appropriate Basal Area Factor (BAF) depends on stand density. BAF 10 is common in dense eastern hardwoods; BAF 20 or higher suits open western timber types. Most foresters carry multiple angle gauges or prisms to adapt to varying stand conditions.
What is the difference between an angle gauge and a wedge prism?
Both angle gauges and wedge prisms perform the same sampling function. A wedge prism is an optical glass prism; an angle gauge is a calibrated frame or stick. Prisms are generally preferred for faster cruising over difficult terrain.
What other forest sampling tools do you carry?
We carry angle gauges, prisms, clinometers, densiometers, increment borers, tree calipers, and diameter tapes.
