Tangent Vectors of Isochron Rays and Velocity Rays Expressed in Global Cartesian Coordinates

This paper provides Cartesian expressions for tangent vectors of isochron rays and velocity rays previously derived in so-called isochron-orthonormal coordinates. The Cartesian expressions are simpler and easier to implement than the expressions in isochron-orthonormal coordinates. It is shown that the expressions in both coordinate systems are equivalent.