¶ Prism
| Company | Remsoft |
| Country | Canada |
| Website | https://remsoft.com/prism/ |
| Category | Planning & Inventory › Remote sensing & mapping |
Forest Inventory Data Collection, Analysis and Reporting
¶ Overview
In forestry, a prism (also known as an angle gauge or wedge prism) is a simple optical tool used in variable-radius plot sampling — a method of forest inventory developed by Austrian forester Walter Bitterlich in the 1940s. The prism is a small wedge of glass that bends (refracts) light, causing a lateral displacement of the image viewed through it. When an observer holds the prism at eye level over a plot centre and views each surrounding tree, the prism image of the tree is offset relative to the direct image; if the offset tree trunk image overlaps or is in line with the direct image, the tree is counted as "in" the sample, and if it is fully displaced, the tree is "out." The probability that a tree is counted is proportional to its basal area, making the prism a basal area factor (BAF) sampling tool — each tree counted represents a fixed amount of stand basal area per hectare, determined by the prism's angle gauge factor. This elegant statistical property means that stand basal area — a key measure of stocking and site occupancy — can be estimated very efficiently with minimal equipment. In Australian native forest inventory and plantation monitoring, prism-based angle count sampling has historically been a standard field method, valued for its speed and low equipment cost relative to fixed-area plot methods. The prism remains relevant today as a cross-check and complement to newer LiDAR-based and photogrammetric inventory methods, and as a teaching tool for understanding the geometric principles underlying variable-radius sampling. It is also used in thinning operations to assess residual stocking after harvesting, and in research plots to calibrate remote sensing-derived basal area estimates.
¶ Assessment
Enhances optimisation and forecasting accuracy, decreasing decision risk and supporting more resilient management strategies.
¶ Details
| Field | Value |
|---|---|
| Company | Remsoft |
| Country | Canada |
| Type | Company |
| FWPA RD&E | 7.3 |