This paper studies two methods to analyze stability of a legged modular robot, designed to move through natural environments with non-coplanar contacts that have different orientations. In order to ensure stability at a contact point, the ground reaction must be contained within a friction cone. Previous works use a linear approximation of the cone to a pyramid, such that the reaction force at the contact point should be a linear combination with non-negative coefficients of the lateral edges that compose the pyramid. In this paper, firstly, the terrain is modeled with a triangular mesh and a subdivision of the triangles is performed to efficiently identify those closest to the robot's feet using k-d trees. Afterwards, the stability of the robot is verified using the pyramidal approximation of the friction cone by comparing two methods: the polytope method and the Newton’s new method.