Prism Basal Area Factor

Convert measured prism deflection angle to metric BAF and sum caller inclusion weights, including explicitly half-counted border trees; sampling protocol determines weights and this is not a fixed-plot tree-area alias.

Description

A prism's angular deflection determines metric basal area factor.

A prism's angular deflection determines metric basal area factor. Inclusion weights, including any half-counted border trees, come from the sampling protocol.^[1]

When to use Prism Basal Area Factor

Use this tool to convert measured prism deflection angle to metric BAF and sum caller inclusion weights, including explicitly half-counted border trees; sampling protocol determines weights and this is not a fixed-plot tree-area alias.

Gather the tree inventory, plot measurements or model parameters. Check diameter, area, time and moisture conventions; keep paired observations aligned.

How to use Prism Basal Area Factor and understand its results

Gather the tree inventory, plot measurements or model parameters. Check diameter, area, time and moisture conventions; keep paired observations aligned.
Enter prismDeflectionAngleDegrees, countedTreeWeights using the field table and calculation rules, then run the tool.
Read basalAreaFactorM2PerHectare, angleCountBasalAreaM2PerHectare. The explanation below defines the units, signs, ordering and any flags or placeholder values.
If the tool reports an input issue, correct the values and run it again. Apply the stated assumptions when interpreting a successfully returned result.

Input field	Meaning	Value type; see rules below	Requirement
prismDeflectionAngleDegrees	Prism deflection angle degrees	number	Required
countedTreeWeights	Counted tree weights	list of number	Required

Use deflection strictly between 0° and 90° and weights in [0,1]. Convert the half-angle and return BAF and angle-count basal area; an empty weight list gives zero basal area.

BAF m²/ha=10,000sin²(deflection degrees × π/360); basal area=BAF × sum tree weights

Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.

Output field	Meaning	Value type
basalAreaFactorM2PerHectare	Basal area factor m2 per hectare	number
angleCountBasalAreaM2PerHectare	Angle count basal area m2 per hectare	number

json

{
  "input": {
    "prismDeflectionAngleDegrees": 1.1459346897143055,
    "countedTreeWeights": [
      1,
      0.5,
      1
    ]
  },
  "output": {
    "basalAreaFactorM2PerHectare": 1,
    "angleCountBasalAreaM2PerHectare": 2.5
  }
}

Limitations and assumptions

Border-tree weights are supplied rather than inferred. This is not fixed-plot expansion.

Numeric inputs and returned numeric values must be finite; an unrepresentable returned value produces an error. Numeric lists are limited to 100,000 entries; the rules above may require smaller limits. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors.

Alternative or Complementary methods

Use Relaskop Critical Distance: Compare slope-corrected horizontal tree distances to angle-count critical radii with a caller borderline tolerance; codes +1/0/-1 mean included/ambiguous/excluded and do not automatically assign border-tree weights. For a complementary task, use Species Importance Value: Calculate the three-component 0–300 importance-value convention from measured stems, basal area and plot occurrences; not percentage dominance alone or ecological importance certification.

References

Prism Basal Area Factor — tool.io

Similar or alternative tools

Relaskop Critical Distance
Compare slope-corrected horizontal tree distances to angle-count critical radii with a caller borderline tolerance; codes +1/0/-1 mean included/ambiguous/excluded and do not automatically assign border-tree weights.
Species Importance Value
Calculate the three-component 0–300 importance-value convention from measured stems, basal area and plot occurrences; not percentage dominance alone or ecological importance certification.