Attribute: GELA [m NN] (horizontal or 3D models only)

The ground level is always required where an impermeable layer is defined (UNDU) or the difference between the ground level and the groundwater level should be computed (ground level - groundwater level = difference between ground and ground water level). Furthermore, the ground level is required to compute the initial and maximum thickness and it can define the topmost node layer in a 3D model. The ground level is always assigned to nodes.

Based on the terrain data the following relief image can be created with the program Surfer: