When viewing in Wireframe, Hidden Line or Patterned display mode in 3D, the terrain is displayed using a mesh pattern. You can adjust the spacing between the grid lines of the mesh pattern.
To edit the grid mesh spacing of the terrain:
Select Settings
> Terrain Settings, or click the Terrain Settings button on
the Settings toolbar.
In the Terrain Settings dialog, edit the value in the Grid Mesh Spacing edit box.
Click OK.