Prism 2 : An optical instrument used as an angle gauge, consisting of a thin wedge of glass that establishes a fixed (critical) angle of projection in a point sample
British Columbia Ministry of Forests and Range, Acronyms and Initialisms for Forestry Terms in British Columbia, Canada 2008. http://www.for.gov.bc.ca/hfd/library/documents/acr onyms/ & http://www.for.gov.bc.ca/hfd/library/documents/glo ssary/Glossary.pdf, (For Fr - Canad) {16}