Näslund Height Curve

Evaluate caller calibrated Näslund h=breast height+(d/(a+b d))² with explicit cm/metre calibration convention; no universal species curve or measured height lookup.

Description

The Näslund height curve relates diameter to height using calibrated coefficients.

The Näslund height curve relates diameter to height using calibrated coefficients. Its coefficient units depend on the centimeter-diameter and meter-height convention.^[1]

Evaluate caller calibrated Näslund h=breast height+(d/(a+b d))² with explicit cm/metre calibration convention; no universal species curve or measured height lookup.

When to use Näslund Height Curve

Use this tool to evaluate caller calibrated Näslund h=breast height+(d/(a+b d))² with explicit cm/metre calibration convention; no universal species curve or measured height lookup.

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

How to use Näslund Height Curve 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 dbhCm, naslundA, naslundB, breastHeightM using the field table and calculation rules, then run the tool.
Read modelTreeHeightsM. 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
dbhCm	Dbh cm	list of number	Required
naslundA	Naslund a	number	Required
naslundB	Naslund b	number	Required
breastHeightM	Breast height m	number	Required

Enter positive DBHs in cm, positive a, nonnegative b and nonnegative breast height in meters. Evaluate model heights in input order; calibrations must use these same units.

height=breast height+(DBH cm/(a+b DBH cm))²

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

Output field	Meaning	Value type
modelTreeHeightsM	Model tree heights m	list of number

json

{
  "input": {
    "dbhCm": [
      10,
      20
    ],
    "naslundA": 1,
    "naslundB": 0.1,
    "breastHeightM": 1.3
  },
  "output": {
    "modelTreeHeightsM": [
      26.3,
      45.74444444444445
    ]
  }
}

Limitations and assumptions

The tool does not fit coefficients or supply a universal species/region curve. A supplied empty diameter list returns an empty result.

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 Chapman-Richards Site Index Height Age: Normalize supplied dominant height/age to a reference-age Chapman–Richards site index with explicit growth/shape calibration; no generic height/age ratio or universal regional site table. For a complementary task, use Merchantable Top Break 4-Inch Spec: Locate a unique measured stem-profile crossing of caller top diameter in inches (four-inch example), converting exactly 2.54 cm/in; no extrapolated taper, invented plateau height or automatic merchantability.

References

Näslund Height Curve — tool.io

Similar or alternative tools

Chapman-Richards Site Index Height Age
Normalize supplied dominant height/age to a reference-age Chapman–Richards site index with explicit growth/shape calibration; no generic height/age ratio or universal regional site table.
Merchantable Top Break 4-Inch Spec
Locate a unique measured stem-profile crossing of caller top diameter in inches (four-inch example), converting exactly 2.54 cm/in; no extrapolated taper, invented plateau height or automatic merchantability.