Please read the vignette.
Or, after installation, the help page:
#> Correction Factors for Tree Plot Areas Intersected by Stand Boundaries
#>
#> Description:
#>
#> The German national forest inventory uses angle count sampling, a
#> sampling method first published by Bitterlich (1947) and extended
#> by Grosenbaugh (1952) as probability proportional to size
#> sampling. When plots are located near stand boundaries, their
#> sizes and hence their probabilities need to be corrected.
#>
#> Details:
#>
#> You will find the details in
#> 'vignette("An_Introduction_to_treePlotArea", package =
#> "treePlotArea")'.
#>
#> References:
#>
#> Bitterlich, W. (1947): Die Winkelzählmessung. Allgemeine Forst-
#> und Holzwirtschaftliche Zeitung, 58.
#>
#> Grosenbaugh, L. R. (1952): Plotless Timber Estimates - New, Fast,
#> Easy. Journal of Forestry.
#> https://academic.oup.com/jof/article-abstract/50/1/32/4684174.
You can install treePlotArea from gitlab via: