How this calculator works
The level-ground method adds eye height to the rise above your horizontal sight line. On a slope, use signed angles to both top and base: positive above horizontal and negative below. Subtracting the tangent heights handles a tree above or below your viewpoint. Shadows instead use similar triangles with an upright reference measured at the same time. All methods assume an identifiable top; a leaning trunk or displaced crown can bias tangent measurements.
Formula
Level: H = D tan(beta) + eye. Slope: H = D[tan(beta) - tan(alpha)]. Shadows: H = reference height x tree shadow / reference shadow.
Worked example
At 10 m horizontal distance, a 45 degree top angle and 1.5 m eye height give 11.5 m. A 2 m reference casting a 3 m shadow beside a tree with a 30 m shadow gives 20 m.
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Frequently asked questions
What sign should the base angle have?
Enter a negative angle when the trunk base is below your horizontal sight line and a positive angle when it is above.
Can I use the walking distance up a hill?
The tangent formula requires horizontal distance. A distance measured along the slope needs a separate horizontal correction.
When do shadows work best?
Use clear shadows cast at the same time on approximately level ground. Wind, diffuse tips and uneven ground increase uncertainty.