[Equivalent Circuit] How is computed a surface resistance?

Hello,

I do not understand how is computed the resistances/conductances between 2 surface nodes.

Here is a situation where it is easy : the resistance between 2 opposite sides of a rectangle surface is the sheet resistance (Ohm / square) times the aspect ratio of the rectangle.

But, it is not obvious to me for a resistance between 2 nodes of a surface meshing.

I can not find any answer in the documentation. Is there a resource more detailed about the equivalent circuit model ? Or any other reference ?

Thank you,

Martin J. Guillon.