# Pile Interaction
The Pile interaction module defines the interface between the nodes on pile and the soil.
# Definition
# Node List
A list of nodes that interact with soil.
Interaction Area
If Automatic is selected, the interaction areas will be calculated by GSA automatically, otherwise, X, Y and Z represent the dimension of the beam section of the pile covered by the interaction nodes. The perimeter is the perimeter length of the pile section that are used by pile-soil vertical shear interaction.
Interaction Elevation
The elevation of the pile nodes interacts with soil. If Automatic is selected, the Z coordinate of the interaction will be used as the interaction elevation. The user defined interaction elevations are relative to elevation used in soil profile.