Determining external surface area.

(A) Brachiosaurus model showing the quadrilateral tessellation used to compute the surface area of the model. The scale bar is 2 m. (B) Decomposition of the nth body surface quadrilateral into two sub-triangles and . Q1, Q2, Q3 and Q4 are the four points defining the vertices of the quadrilateral. The edges of the triangles are represented by vectors between the vertices. One half of the magnitude of the vector cross-product of a pair of co-terminal vectors, eg. and , gives the area of the triangle. See Methods: Surface Area Calculations for more detail.