Lifeform
Vegetation life-form (growth form) classes are defined based on structural similarities of plants.
Three main life-forms are encountered in the nature: woody, herbaceous and lichens/mosses forms.
Identification of life-forms can be performed through human resources (see here). However, this is a long, expensive and fastidious task. Furthermore, all land surface areas are not necessarily accessible to human people. Plant life-form can be automatically identified by satellite/airborne sensors.
Unit: class