In order to estimate the timber capital and the incremental elements of a forest, test surfaces are taken by making the necessary measurements in each of them.
The position of the test surfaces is chosen so as to give in general the average condition of the lumber stock of the cluster.
The procedure for placing on the ground of the test surfaces is the following: First the positions within the cluster are selected, based on the representativeness of the average condition and then the marking of the D.E. with red tape. In addition to their marking on the ground, these areas are also marked on the forestry map and the exact location of each is noted with its geographical coordinates in the EGSA ’87 system. These geographical elements of the test surfaces and their area per cluster are given in the attached table of test surfaces. Finally, on each test surface, all atoms are calibrated and the height of a tree, the diameter of which corresponds to the average circular area, is measured by diameter class.