Early ITU model

The ITU vegetation model is a radio propagation model that estimates the path loss encountered due to the presence of one or more trees inside a point to point telecommunication link. The predictions found from this model is congruent to those found from Weissberger’s modified exponential decay model in low frequencies.
History.
The CCIR, predecessor of ITU, adopted this model in the late 1986.
Coverage.
Frequency: Not specified
Depth of Foliage: Not specified
Mathematical formulation.
The model is formulated as:
formula_1
Where
Points to note.
This equation is scaled for frequency specified in megahertz (MHz).
The depth of foliage must be in the units of meters.
Limitations.
The results of this model gets impractical at high frequencies.
Further reading.
"Introduction to RF Propagation," John S. Seybold, 2005, John Wiley and Sons.